SRv6 Encapsulation in the Base Routing Instance
This chapter provides information about SRv6 encapsulation in the base routing instance.
Topics in this chapter include:
Applicability
The information and configuration in this chapter are based on SR OS Release 22.2.R1. Segment Routing over IPv6 (SRv6) is supported on FP4-based equipment in SR OS Release 21.5.R2 and later.
Overview
SRv6 encapsulation in the base routing instance allows the transport of native IPv4 and IPv6 data across an SRv6-enabled network. To this end, native IPv4 and IPv6 data is sent to an ingress SRv6 router, where it is encapsulated and forwarded via an SRv6 tunnel. The SRv6 tunnel transports the encapsulated data across the SRv6-enabled network to an egress SRv6 router, where it is decapsulated and forwarded further as native IPv4 and IPv6 data. SRv6-tunneled data is encapsulated using an IPv6 header, where the destination address is a unique SRv6 segment identifier (SID), and is processed and forwarded in the IPv6 data plane.
An SRv6 SID is a preconfigured 128-bit routable IPv6 prefix address that is encoded in three parts: a locator, a function, and an argument. The locator is a summary IPv6 prefix for a set of SRv6 SIDs instantiated on an SRv6-capable router. It is used to route the data within the IPv6 transport network. Each participating SRv6-capable router needs its unique locator, based on a common block that all participating SRv6-capable routers share in the IPv6 address space. The function is an opaque identifier that indicates the local behavior at the endpoint of an SRv6 segment. The focus in this topic is on the SRv6 End.DT4 and the SRv6 End.DT6 functions, performing a prefix lookup in the global IPv4 route table (End.DT4) or in the global IPv6 route table (End.DT6). The argument is not used in SR OS 22.2.R1 and is set to all zeros.
The local router installs its locator prefix in its IPv6 route table and Forwarding Information Base (FIB), and advertises its locator prefix in IS-IS with the SRv6 locator sub-TLV. Each remote router populates its route table and FIB with the received locator prefixes, including the tunneled next hop to the originating router.
SRv6 data transport requires additional processing at both the ingress and egress data planes. This processing relies on Forwarding Path Extension (FPE), as described in the Segment Routing over IPv6 chapter.
Configuration
Example topology shows the example topology with five routers. Two routers (CE-1 and CE-2) simulate an IPv6-enabled network. They are connected to an SRv6-enabled network, comprising of PE-1 and PE-2, and a route reflector (RR) RR-3 in the control plane. The SRv6-enabled network has only IPv6 addresses and interfaces.
For the transport of native IPv4 and IPv6 data from CE-1 to CE-2, PE-1 acts as the SRv6 ingress PE node, while PE-2 acts as the SRv6 egress PE node. For the transport of native IPv4 and IPv6 data from CE-2 to CE-1, PE-2 acts as the SRv6 ingress PE node, while PE-1 acts as the SRv6 egress PE node. To explain the SRv6 encapsulation concept, the topology does not need an SRv6 transit router because SRv6 transit routers simply forward SRv6-encapsulated packets via IPv6 route table lookup without any other processing.
SRv6 and FPE are configured only on PE-1 and on PE-2. RR-3 acts as the BGP RR in the control plane and does not participate in the SRv6 data transport that only exists between PE-1 and PE-2.
The ping and traceroute commands between IPv4 and IPv6 system addresses of CE-1 and CE-2 simulate data transport.
The configuration for this example topology is completely symmetrical. All configure and show command outputs for PE-1 also apply for PE-2, and similar for CE-1 and CE-2.
The following sections describe the configuration steps needed to establish SRv6 Encapsulation in the base routing instance.
Configure the transport network:
This configuration includes:
- ports and IPv6-only interfaces on PE-1, PE-2, and RR-3
- port cross connect (PXC) and FPE on PE-1 and PE-2 (using internal loopbacks on an FP4 MAC chip), as described in the Segment Routing over IPv6 chapter .
- IS-IS on PE-1, PE-2, and RR-3 including:
- level 2 capability with wide metrics (for the 128-bit identifiers)
- native IPv6 routing
- as best practice, include also: traffic-engineering and traffic-engineering-options on PE-1 and PE-2
- advertise the router capability within the autonomous system (AS) (not for RR-3)
- BGP on PE-1, PE-2, and RR-3, with internal group “gr_v6_internal” that
includes:
- IPv4 and IPv6 address families
- extended-nh-encoding for IPv4
- advertise-ipv6-next-hops for IPv4
- next-hop-self (not for RR-3)
- BGP neighbor system IPv6 addresses
The core network topology uses IPv6 for BGP peering (with 16-byte next hop addresses), so to advertise and receive IPv4 routes (which have 4-byte next hop addresses) with IPv6 next hop addresses the commands advertise-ipv6-next-hops and extended-nh-encoding need to be configured at the BGP, group, or neighbor level. The advertise-ipv6-next-hops command instructs the system to advertise IPv4 routes with an IPv6 next hop address. The extended-nh-encoding command configures BGP to advertise the capability to receive IPv4 routes with an IPv6 next hop address.
The following example configuration applies for PE-1 and is similar for PE-2.
The following example configuration applies for RR-3:
[/]
A:admin@PE-1# configure {
router "Base" {
autonomous-system 64500
interface "int-PE-1-PE-2" {
description "interface between PE-1 and PE-2"
port 1/1/c1/1:1000
ipv6 {
address 2001:db8::168:12:1 {
prefix-length 126
}
}
}
interface "int-PE-1-RR-3" {
description "interface between PE-1 and RR-3"
port 1/1/c2/1:1000
ipv6 {
address 2001:db8::168:13:1 {
prefix-length 126
}
}
}
interface "system" {
description "system interface of PE-1"
ipv6 {
address 2001:db8::2:1 {
prefix-length 128
}
}
}
isis 0 {
admin-state enable
advertise-router-capability as
ipv6-routing native
level-capability 2 # required for SRv6
router-id 1.1.1.1
traffic-engineering true
area-address [49.0001]
traffic-engineering-options {
ipv6 true
application-link-attributes {
}
}
interface "int-PE-1-PE-2" {
interface-type point-to-point
}
interface "int-PE-1-RR-3" {
interface-type point-to-point
}
interface "system" {
passive true
}
level 2 {
wide-metrics-only true # required for SRv6
}
}
bgp {
min-route-advertisement 1
router-id 2.2.2.1
rapid-withdrawal true
split-horizon true
ebgp-default-reject-policy {
import false # do not refuse eBGP imported policies
export false # do not prevent eBGP exported policies
}
group "gr_v6_internal" {
description "internal bgp group on PE-1"
next-hop-self true
type internal
family {
ipv4 true
ipv6 true
}
extended-nh-encoding {
ipv4 true
}
advertise-ipv6-next-hops {
ipv4 true
}
}
neighbor "2001:db8::2:3" { # RR-3 system address
group "gr_v6_internal"
}
}
exit all
The following example configuration applies for RR-3:
[/]
A:admin@RR-3# configure {
router "Base" {
autonomous-system 64500
interface "int-RR-3-PE-1" {
description "interface between RR-3 and PE-1"
port 1/1/c1/1:1000
ipv6 {
address 2001:db8::168:13:2 {
prefix-length 126
}
}
}
interface "int-RR-3-PE-2" {
description "interface between RR-3 and PE-2"
port 1/1/c2/1:1000
ipv6 {
address 2001:db8::168:23:2 {
prefix-length 126
}
}
}
interface "system" {
description "system interface of RR-3"
ipv6 {
address 2001:db8::2:3 {
prefix-length 128
}
}
}
isis 0 {
admin-state enable
ipv6-routing native
level-capability 2 # required for SRv6
router-id 1.1.1.3
area-address [49.0001]
interface "int-RR-3-PE-1" {
interface-type point-to-point
}
interface "int-RR-3-PE-2" {
interface-type point-to-point
}
interface "system" {
passive true
}
level 2 {
wide-metrics-only true # required for SRv6
}
}
bgp {
min-route-advertisement 1
router-id 2.2.2.3
rapid-withdrawal true
split-horizon true
group "gr_v6_internal" {
description "internal bgp group on RR-3"
type internal
family {
ipv4 true
ipv6 true
}
cluster {
cluster-id 3.3.3.3
}
extended-nh-encoding {
ipv4 true
}
advertise-ipv6-next-hops {
ipv4 true
}
}
neighbor "2001:db8::2:1" { # PE-1 system address
group "gr_v6_internal"
}
neighbor "2001:db8::2:2" { # PE-2 system address
group "gr_v6_internal"
}
}
exit all
Configure CE-1 and CE-2 for native IPv4 and IPv6 data
This configuration includes:
- ports and IPv4 and IPv6 interfaces between CE-1 and PE-1 and between CE-2 and PE-2
- an IPv4 system address and an IPv6 system address for CE-1 and for CE-2
- BGP, with external group “gr_v6_external” that includes the following
capabilities:
- IPv4 and IPv6 address families
extended-nh-encodingfor IPv4advertise-ipv6-next-hopsfor IPv4- BGP neighbor interface IPv6 addresses, with BGP neighbors in a different external autonomous system
The following example configuration applies for PE-1 and is similar for PE-2. The strip-srv6-tlvs command (per address family) prevents PE-1 from advertising SRv6 TLVs to the BGP neighbor.
[/]
A:admin@PE-1# configure {
router "Base" {
interface "int-PE-1-CE-1" {
description "interface between PE-1 and CE-1"
port 1/1/c6/1:1000
ipv4 {
primary {
address 172.16.14.1
prefix-length 30
}
}
ipv6 {
address 2001:db8::168:14:1 {
prefix-length 126
}
}
}
bgp {
group "gr_v6_external" {
description "external bgp group on PE-1"
family {
ipv4 true
ipv6 true
}
extended-nh-encoding {
ipv4 true
}
advertise-ipv6-next-hops {
ipv4 true
}
}
neighbor "2001:db8::168:14:2" {
group "gr_v6_external"
type external
peer-as 64504
segment-routing-v6 {
route-advertisement {
family ipv4 {
strip-srv6-tlvs true
}
family ipv6 {
strip-srv6-tlvs true
}
}
}
}
}
exit all
The following example configuration applies for CE-2 and is similar for CE-1.
[/]
A:admin@CE-2# configure {
router "Base" {
autonomous-system 64505
interface "int-CE-2-PE-2" {
description "interface between CE-2 and PE-2"
port 1/1/c1/1:1000
ipv4 {
primary {
address 172.16.25.2
prefix-length 30
}
}
ipv6 {
address 2001:db8::168:25:2 {
prefix-length 126
}
}
}
interface "system" {
description "system interface of CE-2"
ipv4 {
primary {
address 192.0.2.5 # used for IPv4 ping
prefix-length 32
}
}
ipv6 {
address 2001:db8::2:5 { # used for IPv6 ping
prefix-length 128
}
}
}
bgp {
min-route-advertisement 1
router-id 2.2.2.5
rapid-withdrawal true
split-horizon true
ebgp-default-reject-policy {
import false # do not refuse eBGP imported policies
export false # do not prevent eBGP exported policies
}
group "gr_v6_external" {
description "external bgp group on CE-2"
family {
ipv4 true
ipv6 true
}
extended-nh-encoding {
ipv4 true
}
advertise-ipv6-next-hops {
ipv4 true
}
}
neighbor "2001:db8::168:25:1" {
group "gr_v6_external"
type external
peer-as 64500
}
}
exit all
Ensure the export of the system addresses of CE-1 and CE-2
Configure a policy on CE-2 that imports the IPv4 and IPv6 prefixes into BGP. Configure a similar policy on CE-1.
[/]
A:admin@CE-2# configure {
policy-options {
prefix-list "CE-2_prefixes" {
prefix 192.0.2.5/32 type exact {
}
prefix 2001:db8::2:5/128 type exact {
}
}
policy-statement "policy-export-bgp" {
entry 10 {
from {
prefix-list ["CE-2_prefixes"]
}
action {
action-type accept
}
}
}
exit all
Apply this policy on CE-2 to the BGP neighbor PE-2. Perform a similar configuration on CE-1 to the BGP neighbor PE-1.
[ex:/configure router "Base"]
A:admin@CE-2#
bgp {
neighbor "2001:db8::168:25:1" {
export {
policy ["policy-export-bgp"]
}
}
exit all
Verify the IPv4 and IPv6 route tables. The corresponding FIBs can be verified with the show router fib 1 ipv4 and show router fib 1 ipv6 commands.
On CE-1:
192.0.2.4/32 is the IPv4 system address of CE-1. 192.0.2.5/32 is the IPv4 system address of CE-2, which is reached via PE-1.
[/]
A:admin@CE-1# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.14.0/30 Local Local 00h05m19s 0
int-CE-1-PE-1 0
192.0.2.4/32 Local Local 00h05m19s 0
system 0
192.0.2.5/32 Remote BGP 00h00m26s 170
2001:db8::168:14:1 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
2001:db8::2:4/128 is the IPv6 system address of CE-1. 2001:db8::2:5/128 is the IPv6 system address of CE-2, which is reached via PE-1.
[/]
A:admin@CE-1# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
2001:db8::2:4/128 Local Local 00h05m19s 0
system 0
2001:db8::2:5/128 Remote BGP 00h00m26s 170
2001:db8::168:14:1 0
2001:db8::168:14:0/126 Local Local 00h05m18s 0
int-CE-1-PE-1 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
On PE-1:
[/]
A:admin@PE-1# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.14.0/30 Local Local 00h06m21s 0
int-PE-1-CE-1 0
192.0.2.4/32 Remote BGP 00h00m40s 170
2001:db8::168:14:2 0
192.0.2.5/32 Remote BGP 00h00m21s 170
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
[/]
A:admin@PE-1# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
2001:db8::2:1/128 Local Local 00h12m43s 0
system 0
2001:db8::2:2/128 Remote ISIS 00h11m03s 18
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
2001:db8::2:3/128 Remote ISIS 00h10m52s 18
fe80::612:1ff:fe01:1-"int-PE-1-RR-3" 10
2001:db8::2:4/128 Remote BGP 00h00m40s 170
2001:db8::168:14:2 0
2001:db8::2:5/128 Remote BGP 00h00m21s 170
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
2001:db8::168:12:0/126 Local Local 00h12m43s 0
int-PE-1-PE-2 0
2001:db8::168:13:0/126 Local Local 00h12m42s 0
int-PE-1-RR-3 0
2001:db8::168:14:0/126 Local Local 00h06m20s 0
int-PE-1-CE-1 0
2001:db8::168:23:0/126 Remote ISIS 00h11m03s 18
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 20
-------------------------------------------------------------------------------
No. of Routes: 9
---snip---
===============================================================================
On PE-2:
[/]
A:admin@PE-2# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.25.0/30 Local Local 00h06m04s 0
int-PE-2-CE-2 0
192.0.2.4/32 Remote BGP 00h00m42s 170
fe80::60a:1ff:fe01:1-"int-PE-2-PE-1" 10
192.0.2.5/32 Remote BGP 00h00m24s 170
2001:db8::168:25:2 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
[/]
A:admin@PE-2# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
2001:db8::2:1/128 Remote ISIS 00h11m00s 18
fe80::60a:1ff:fe01:1-"int-PE-2-PE-1" 10
2001:db8::2:2/128 Local Local 00h12m27s 0
system 0
2001:db8::2:3/128 Remote ISIS 00h10m54s 18
fe80::612:1ff:fe01:b-"int-PE-2-RR-3" 10
2001:db8::2:4/128 Remote BGP 00h00m42s 170
fe80::60a:1ff:fe01:1-"int-PE-2-PE-1" 10
2001:db8::2:5/128 Remote BGP 00h00m24s 170
2001:db8::168:25:2 0
2001:db8::168:12:0/126 Local Local 00h12m26s 0
int-PE-2-PE-1 0
2001:db8::168:13:0/126 Remote ISIS 00h11m00s 18
fe80::60a:1ff:fe01:1-"int-PE-2-PE-1" 20
2001:db8::168:23:0/126 Local Local 00h12m26s 0
int-PE-2-RR-3 0
2001:db8::168:25:0/126 Local Local 00h06m03s 0
int-PE-2-CE-2 0
-------------------------------------------------------------------------------
No. of Routes: 9
---snip---
===============================================================================
IPv4 data transport is not possible between CE-1 and CE-2. Verify this with a ping from CE-1 to the IPv4 system address that CE-2 advertises.
[/]
A:admin@CE-1# ping 192.0.2.5
PING 192.0.2.5 56 data bytes
... ... ... ... . Request timed out. icmp_seq=1.
Request timed out. icmp_seq=2.
---snip---
---- 192.0.2.5 PING Statistics ----
5 packets transmitted, 0 packets received, 100% packet loss
IPv6 data transport is possible between CE-1 and CE-2, although not by using SRv6 between PE-1 and PE-2 but by using native IPv6. Verify this with a ping and a traceroute from CE-1 to the IPv6 system address that CE-2 advertises. Native IPv6 data flows over an IPv6 interface from CE-1 to PE-1, from there over an IPv6 interface to PE-2, and from there over an IPv6 interface to CE-2. The same is true for data transport between CE-2 and CE-1.
[/]
A:admin@CE-1# ping 2001:db8::2:5
PING 2001:db8::2:5 56 data bytes
64 bytes from 2001:db8::2:5 icmp_seq=1 hlim=62 time=2.18ms.
---snip---
---- 2001:db8::2:5 PING Statistics ----
5 packets transmitted, 5 packets received, 0.00% packet loss
round-trip min = 1.85ms, avg = 2.07ms, max = 2.18ms, stddev = 0.122ms
[/]
A:admin@CE-1# traceroute 2001:db8::2:5
traceroute to 2001:db8::2:5, 30 hops max, 60 byte packets
1 2001:db8::168:14:1 (2001:db8::168:14:1) 1.02 ms 0.790 ms 0.837 ms
2 2001:db8::168:12:2 (2001:db8::168:12:2) 1.28 ms 1.26 ms 1.41 ms
3 2001:db8::2:5 (2001:db8::2:5) 1.80 ms 1.99 ms 1.82 ms
Configure SRv6 in the router Base context on PE-1 and PE-2
Configure the locator in the router Base segment-routing segment-routing-v6 context on PE-2. Perform a similar configuration on PE-1, with ip-prefix 2001:db8:aaaa:101::/64 for locator “PE-1_loc”.
[ex:/configure router "Base" segment-routing]
A:admin@PE-2#
segment-routing-v6 {
locator "PE-2_loc" {
admin-state enable
block-length 48
prefix {
ip-prefix 2001:db8:aaaa:102::/64
}
}
exit all
Configure the FPEs on PE-1 and PE-2.
[ex:/configure]
A:admin@PE-2#
fwd-path-ext {
fpe 1 {
path {
pxc 1
}
application {
srv6 {
type origination
}
}
}
fpe 2 {
path {
pxc 2
}
application {
srv6 {
type termination
}
}
}
exit all
Use FPE 1 as the SRv6 origination FPE in the router Base segment-routing segment-routing-v6 context and FPE 2 as the SRv6 termination FPE in the router Base segment-routing segment-routing-v6 locator context on PE-2. Perform a similar configuration on PE-1 for locator “PE-1_loc”.
[ex:/configure router "Base" segment-routing]
A:admin@PE-2#
segment-routing-v6 {
origination-fpe [1]
locator "PE-2_loc" {
admin-state enable
termination-fpe [2]
}
exit all
Configure the SRv6 End function (equivalent to an IPv4 node SID) and SRv6 End.X functions (equivalent to IPv4 Adjacency SIDs) in the router Base segment-routing segment-routing-v6 base-routing-instance locator context on PE-2. Perform a similar configuration on PE-1 for locator “PE-1_loc”.
[ex:/configure router "Base" segment-routing]
A:admin@PE-2#
segment-routing-v6 {
base-routing-instance {
locator "PE-2_loc" {
function {
end 1 {
srh-mode usp
}
end-x-auto-allocate psp protection unprotected { }
}
}
}
exit all
Advertise the locator in IS-IS while ensuring level 2 capability on PE-2. Perform a similar configuration on PE-1 for locator “PE-1_loc”.
[ex:/configure router "Base" isis 0]
A:admin@PE-2#
segment-routing-v6 {
admin-state enable
locator "PE-2_loc" {
level-capability 2
}
exit all
A summary on locator and origination FPE configuration can be verified with the show router segment-routing-v6 summary command.
Verify the SRv6 local SIDs on PE-2 and similar on PE-1. Three SRv6 local SIDs are created: one for the statically configured SRv6 End function (configured in the base context) and two for the auto-allocated SRv6 End.X functions (one facing PE-1 and one facing RR-3). All three SRv6 local SIDs are concatenated with the locator. The statically configured SRv6 End function appears first with function number 1. The auto-allocated SRv6 End.X functions get subsequent function numbers, 2 and 4 respectively. RR-3 has no SRv6 configuration and does not have these SRv6 local SIDs and SRv6 functions.
[/]
A:admin@PE-2# show router segment-routing-v6 local-sid
===============================================================================
Segment Routing v6 Local SIDs
===============================================================================
SID Type Function
Locator
Context
-------------------------------------------------------------------------------
2001:db8:aaaa:102:0:1000:: End 1
PE-2_loc
Base
2001:db8:aaaa:102:0:2000:: End.X 2
PE-2_loc
None
2001:db8:aaaa:102:0:4000:: End.X 4
PE-2_loc
None
-------------------------------------------------------------------------------
SIDs : 3
-------------------------------------------------------------------------------
===============================================================================
Verify the SRv6 base routing instance details on PE-2 and similar on PE-1. The SRv6 End function is statically configured. There is an auto-allocated SRv6 End.X function for each IS-IS neighbor.
[/]
A:admin@PE-2# show router segment-routing-v6 base-routing-instance
===============================================================================
Segment Routing v6 Base Routing Instance
===============================================================================
Locator
Type Function SID Status/InstId
SRH-mode Protection Interface
-------------------------------------------------------------------------------
PE-2_loc
End 1 2001:db8:aaaa:102:0:1000:: ok
USP
-------------------------------------------------------------------------------
Auto-allocated End.X: PSP Unprotected,
-------------------------------------------------------------------------------
End.X *2 2001:db8:aaaa:102:0:2000:: 0
PSP Unprotected int-PE-2-PE-1
ISIS Level: L2 Mac Address: 04:0a:01:01:00:01 Nbr Sys Id: 0010.0100.1001
End.X *4 2001:db8:aaaa:102:0:4000:: 0
PSP Unprotected int-PE-2-RR-3
ISIS Level: L2 Mac Address: 04:12:01:01:00:0b Nbr Sys Id: 0010.0100.1003
-------------------------------------------------------------------------------
===============================================================================
Legend: * - System allocated
Verify the IPv6 route table on PE-1. The IPv6 route table has also routes to the local and the learned remote locators and to the local SRv6 function SIDs. The remotely configured locator prefix of PE-2 is reached via an SRv6 tunnel. The routes with protocol “SRv6” correspond with the locally configured locator prefix of PE-1, or the locally configured SRv6 End function.
[/]
A:admin@PE-1# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
---snip---
2001:db8:aaaa:101::/64 Local SRV6 00h02m44s 3
fe80::201-"_tmnx_fpe_2.a" 0
2001:db8:aaaa:101:0:1000::/128 Local SRV6 00h01m33s 3
Black Hole 0
2001:db8:aaaa:101:0:2000::/128 Local ISIS 00h00m45s 18
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
2001:db8:aaaa:101:0:4000::/128 Local ISIS 00h00m45s 18
fe80::612:1ff:fe01:1-"int-PE-1-RR-3" 10
2001:db8:aaaa:102::/64 Remote ISIS 00h00m31s 18
2001:db8:aaaa:102::/64 (tunneled:SRV6-ISIS) 10
-------------------------------------------------------------------------------
No. of Routes: 14
---snip---
===============================================================================
Verify the IS-IS routes on PE-1 and similar on PE-2. This corresponds with the information in the route table (and FIB). IS-IS is not configured on CE-1 and CE-2, so CE-1 and CE-2 have no IS-IS routes.
[/]
A:admin@PE-1# show router isis routes
===============================================================================
Rtr Base ISIS Instance 0 Route Table
===============================================================================
Prefix[Flags] Metric Lvl/Typ Ver. SysID/Hostname
NextHop MT AdminTag/SID[F]
-------------------------------------------------------------------------------
2001:db8::2:1/128 0 2/Int. 2 PE-1
:: 0 0
2001:db8::2:2/128 10 2/Int. 9 PE-2
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 0 0
2001:db8::2:3/128 10 2/Int. 9 RR-3
fe80::612:1ff:fe01:1-"int-PE-1-RR-3" 0 0
2001:db8::168:12:0/126 10 2/Int. 4 PE-1
:: 0 0
2001:db8::168:13:0/126 10 2/Int. 4 PE-1
:: 0 0
2001:db8::168:23:0/126 20 2/Int. 9 PE-2
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 0 0
2001:db8:aaaa:101::/64 0 2/Int. 11 PE-1
:: 0 0
2001:db8:aaaa:102::/64 10 2/Int. 10 PE-2
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 0 0
-------------------------------------------------------------------------------
No. of Routes: 8 (8 paths)
---snip---
===============================================================================
The locator prefixes and who advertises them can be verified with the show router isis segment-routing-v6 locator command. The SRv6 End SIDs and who advertises them can be verified with the show router isis segment-routing-v6 end-sid command.
The IS-IS data base can be verified with the show router isis database detail command.
The output of this command provides information on each IS-IS-enabled router. Per uniquely identified IS-IS-enabled router, the SRv6 information indicates:
- the IS-IS-advertised router capabilities
- the advertised SRv6 locator TLV
- the advertised configured SRv6 End SID and auto-allocated SRv6 End.X SIDs
The BGP groups can be verified with the show router bgp group command. PE-1 and PE-2 know the iBGP and eBGP peers. RR-3 only knows the iBGP peers. CE-1 and CE-2 only know the eBGP peers.
The BGP next hops can be verified with the show router bgp next-hop ipv4 and show router bgp next-hop ipv6 commands.
Configure SRv6 End.DT4 and SRv6 End.DT6 functions on PE-1 and PE-2
Configure SRv6 End.DT4 and SRv6 End.DT6 functions in the router Base segment-routing segment-routing-v6 base-routing-instance locator function context on PE-1. They can have statically or automatically allocated values. For statically allocated values, an SRv6 reserved label block must be configured. Perform an identical configuration on PE-2.
[ex:/configure router "Base"]
A:admin@PE-1#
mpls-labels {
sr-labels {
start 20000
end 20999
}
reserved-label-block "SRv6" {
start-label 30100
end-label 30199
}
exit all
This SRv6 reserved label block must be referenced in the router Base segment-routing segment-routing-v6 locator static-function context on PE-2, where also the total number of static functions, including the already existing SRv6 End function (with value 1), must be set. Perform a similar configuration on PE-1 for locator “PE-1_loc”.
[ex:/configure router "Base" segment-routing]
A:admin@PE-2#
segment-routing-v6 {
source-address 2001:db8::2:2
locator "PE-2_loc" {
admin-state enable
static-function {
max-entries 3
label-block "SRv6"
}
}
base-routing-instance {
locator "PE-2_loc" {
function {
end-dt4 {
value 2
}
end-dt6 {
value 3
}
}
}
}
exit all
The SRv6 End.DT4 and SRv6 End.DT6 functions are allocated the unique static values of 2 and 3 respectively. The values allocated must not exceed the max-entries value.
Each PE must resolve the BGP next hop to an SRv6 End.DT4 or End.DT6 Segment ID. Therefore, each PE must advertise route prefixes within a BGP update message that includes an SRv6 Services TLV. This is achieved by configuring the add-srv6-tlvs command along with the locator value for each address family, IPv4 and IPv6.
When a PE receives a BGP update that includes the SRv6 Services TLV, the default behavior is to ignore this TLV, and resolve the next hop to the tunnel type configured in an auto-bind-tunnel statement. To override this behavior, ignore-received-srv6-tlvs must be set to false for IPv4 and IPv6 address families on PE-1. Perform a similar configuration on PE-2 for locator “PE-2_loc”.
[ex:/configure router "Base" bgp]
A:admin@PE-1#
segment-routing-v6 {
family ipv4 {
ignore-received-srv6-tlvs false
add-srv6-tlvs {
locator-name "PE-1_loc"
}
}
family ipv6 {
ignore-received-srv6-tlvs false
add-srv6-tlvs {
locator-name "PE-1_loc"
}
}
exit all
CE-2 sends BGP updates to PE-2 for the IPv4 and the IPv6 address families respectively. Each BGP update advertises the IPv4 or IPv6 address family, the reachable network prefixes, and the autonomous system to which they belong. PE-2 adds an SRv6 Services TLV, indicating that resolution to an SRv6 SID is available, making use of the endpoint behavior that is configured for the IPv4 or IPv6 address family on the locator. PE-2 advertises the BGP updates to PE-1 via the RR. PE-1 programs the route prefixes in its route table and FIB with an SRv6 tunnel next hop, and forwards the BGP updates to CE-1. CE-1 programs the learned route prefixes in its route table and FIB.
Similar BGP updates flow from CE-1 to CE-2, via PE-1, RR-3, and PE-2. PE-1 and PE-2 advertise only the SRv6 SIDs for the SRv6 End.DT4 and SRv6 End.DT6 functions.
After the BGP updates, the IS-IS data base remains the same, except for the renumbering of the SRv6 End.X functions. This can be verified with the show router isis database detail command.
The BGP next hops remain the same, except for the next hops to the system addresses of PE-1 and PE-2 that switch owner from “ISIS” to “N/A”. This can be verified with the show router bgp next-hop ipv4 and show router bgp next-hop ipv6 commands.
When debug logging for BGP updates is configured, the configuration results in the following BGP update logs for the IPv4 address family.
Focus as an example on prefix 192.0.2.5/32 and on prefix 192.0.2.4.1/32, but in the other direction.
Verify the IPv4 BGP routes.
CE-2 advertises route prefix 192.0.2.5/32 to PE-2 (in RIB Out Entries).
[/]
A:admin@CE-2# show router bgp routes 192.0.2.5 hunt
===============================================================================
BGP Router ID:2.2.2.5 AS:64505 Local AS:64505
===============================================================================
---snip---
===============================================================================
BGP IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::168:25:2
Path Id : None
To : 2001:db8::168:25:1
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : n/a Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : n/a
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.2
Origin : IGP
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
PE-2 receives the BGP update which CE-2 sends for the IPv4 address family:
[/]
A:admin@PE-2# show log log-id "log_2"
---snip---
5 2022/07/19 11:29:41.236 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::168:25:2
"Peer 1: 2001:db8::168:25:2: UPDATE
Peer 1: 2001:db8::168:25:2 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 43
Flag: 0x90 Type: 14 Len: 26 Multiprotocol Reachable NLRI:
Address Family IPV4
NextHop len 16 Global NextHop 2001:db8::168:25:2
192.0.2.5/32
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 6 AS Path:
Type: 2 Len: 1 < 64505 >
"
---snip---
Upon receipt of the BGP update from CE-2, PE-2 programs route prefix 192.0.2.5/32 in its route table and FIB, with the interface towards CE-2 as next hop.
Verify the resulting IPv4 route table on PE-2:
[/]
A:admin@PE-2# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.25.0/30 Local Local 00h16m25s 0
int-PE-2-CE-2 0
192.0.2.4/32 Remote BGP 00h00m49s 170
2001:db8:aaaa:101:0:2000:: (tunneled:SRV6) 10
192.0.2.5/32 Remote BGP 00h10m45s 170
2001:db8::168:25:2 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
Verify the corresponding IPv4 BGP routes on PE-2:
[/]
A:admin@PE-2# show router bgp routes 192.0.2.5 hunt
===============================================================================
BGP Router ID:2.2.2.2 AS:64500 Local AS:64500
===============================================================================
---snip---
===============================================================================
BGP IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::168:25:2
Path Id : None
From : 2001:db8::168:25:2
Res. Protocol : LOCAL Res. Metric : 0
Res. Nexthop : 2001:db8::168:25:2
Local Pref. : None Interface Name : int-PE-2-CE-2
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.5
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : External
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h10m45s
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::2:2
Path Id : None
To : 2001:db8::2:3
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : 100 Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.3
Origin : IGP
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
SRv6 TLV Type : SRv6 L3 Service TLV (5)
SRv6 SubTLV : SRv6 SID Information (1)
Sid : 2001:db8:aaaa:102:0:2000::
Behavior : End.DT4 (19)
SRv6 SubSubTLV : SRv6 SID Structure (1)
Loc-Block-Len : 48 Loc-Node-Len : 16
Func-Len : 20 Arg-Len : 0
Tpose-Len : 0 Tpose-offset : 0
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
PE-2 then advertises route prefix 192.0.2.5/32 (in RIB Out Entries), via RR-3, and inserts the SRv6 Services TLV. This TLV carries an SRv6 Service Information sub-TLV that contains the End.DT4 SID.
PE-1 receives (via RR-3) the BGP update which PE-2 sends for the IPv4 address family:
[/]
A:admin@PE-1# show log log-id "log_2"
---snip---
3 2022/07/19 11:39:38.404 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::2:3
"Peer 1: 2001:db8::2:3: UPDATE
Peer 1: 2001:db8::2:3 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 104
Flag: 0x90 Type: 14 Len: 26 Multiprotocol Reachable NLRI:
Address Family IPV4
NextHop len 16 Global NextHop 2001:db8::2:2
192.0.2.5/32
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 6 AS Path:
Type: 2 Len: 1 < 64505 >
Flag: 0x40 Type: 5 Len: 4 Local Preference: 100
Flag: 0x80 Type: 9 Len: 4 Originator ID: 2.2.2.2
Flag: 0x80 Type: 10 Len: 4 Cluster ID:
3.3.3.3
Flag: 0xc0 Type: 40 Len: 37 Prefix-SID-attr:
SRv6 Services TLV (37 bytes):-
Type: SRV6 L3 Service TLV (5)
Length: 34 bytes, Reserved: 0x0
SRv6 Service Information Sub-TLV (33 bytes)
Type: 1 Len: 30 Rsvd1: 0x0
SRv6 SID: 2001:db8:aaaa:102:0:2000::
SID Flags: 0x0 Endpoint Behavior: 0x13 Rsvd2: 0x0
SRv6 SID Sub-Sub-TLV
Type: 1 Len: 6
BL:48 NL:16 FL:20 AL:0 TL:0 TO:0
"
---snip---
Upon receipt of the BGP update from RR-3 on behalf of PE-2, PE-1 programs route prefix 192.0.2.5/32 in its route table and FIB. The presence of the SRv6 Services TLV indicates that the next hop is the SRv6 End.DT4 SID which, in turn, is resolved to the remote locator for PE-2.
PE-1 then advertises route prefix 192.0.2.5/32 to CE-1 (in RIB Out Entries).
Verify the resulting IPv4 route table on PE-1. The IPv4 route table has a route to the remote IPv4 system address of CE-2, via the End.DT4 SID of the remotely configured locator prefix of PE-2.
[/]
A:admin@PE-1# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.14.0/30 Local Local 00h16m41s 0
int-PE-1-CE-1 0
192.0.2.4/32 Remote BGP 00h11m01s 170
2001:db8::168:14:2 0
192.0.2.5/32 Remote BGP 00h00m46s 170
2001:db8:aaaa:102:0:2000:: (tunneled:SRV6) 10
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
Verify the corresponding IPv4 BGP routes on PE-1:
[/]
A:admin@PE-1# show router bgp routes 192.0.2.5 hunt
===============================================================================
BGP Router ID:2.2.2.1 AS:64500 Local AS:64500
===============================================================================
---snip---
===============================================================================
BGP IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::2:2
Path Id : None
From : 2001:db8::2:3
Res. Protocol : ISIS Res. Metric : 10
Res. Nexthop : fe80::60e:1ff:fe01:1
Local Pref. : 100 Interface Name : int-PE-1-PE-2
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 10
Connector : None
Community : No Community Members
Cluster : 3.3.3.3
Originator Id : 2.2.2.2 Peer Router Id : 2.2.2.3
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : Internal
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h00m46s
SRv6 TLV Type : SRv6 L3 Service TLV (5)
SRv6 SubTLV : SRv6 SID Information (1)
Sid : 2001:db8:aaaa:102:0:2000::
Behavior : End.DT4 (19)
SRv6 SubSubTLV : SRv6 SID Structure (1)
Loc-Block-Len : 48 Loc-Node-Len : 16
Func-Len : 20 Arg-Len : 0
Tpose-Len : 0 Tpose-offset : 0
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::168:14:1
Path Id : None
To : 2001:db8::168:14:2
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : n/a Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 10
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.4
Origin : IGP
AS-Path : 64500 64505
Route Tag : 0
Neighbor-AS : 64500
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
CE-1 receives the BGP update which PE-1 sends for the IPv4 address family:
[/]
A:admin@CE-1# show log log-id "log_2"
---snip---
1 2022/07/19 11:39:39.220 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::168:14:1
"Peer 1: 2001:db8::168:14:1: UPDATE
Peer 1: 2001:db8::168:14:1 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 47
Flag: 0x90 Type: 14 Len: 26 Multiprotocol Reachable NLRI:
Address Family IPV4
NextHop len 16 Global NextHop 2001:db8::168:14:1
192.0.2.5/32
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 10 AS Path:
Type: 2 Len: 2 < 64500 64505 >
"
---snip---
Upon receipt of the BGP update from PE-1, CE-1 programs route prefix 192.0.2.5/32 in its route table and FIB with the interface towards PE-1 as the next hop.
Verify the resulting IPv4 route table on CE-1:
[/]
A:admin@CE-1# show router route-table ipv4
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.16.14.0/30 Local Local 00h15m40s 0
int-CE-1-PE-1 0
192.0.2.4/32 Local Local 00h15m40s 0
system 0
192.0.2.5/32 Remote BGP 00h00m51s 170
2001:db8::168:14:1 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
Verify the corresponding IPv4 BGP routes on CE-1:
[/]
A:admin@CE-1# show router bgp routes 192.0.2.5 hunt
===============================================================================
BGP Router ID:2.2.2.4 AS:64504 Local AS:64504
===============================================================================
---snip---
===============================================================================
BGP IPv4 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 192.0.2.5/32
Nexthop : 2001:db8::168:14:1
Path Id : None
From : 2001:db8::168:14:1
Res. Protocol : LOCAL Res. Metric : 0
Res. Nexthop : 2001:db8::168:14:1
Local Pref. : None Interface Name : int-CE-1-PE-1
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.1
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : External
AS-Path : 64500 64505
Route Tag : 0
Neighbor-AS : 64500
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h00m51s
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
Similar BGP update logs are generated for the IPv6 address family.
Focus as an example on prefix 2001:db8::2:5/128 and on prefix 2001:db8::2:4/128, but in the other direction.
Verify the IPv6 BGP routes.
CE-2 advertises route prefix 2001:db8::2:5/128 to PE-2 (in RIB Out Entries).
[/]
A:admin@CE-2# show router bgp routes 2001:db8::2:5/128 hunt
===============================================================================
BGP Router ID:2.2.2.5 AS:64505 Local AS:64505
===============================================================================
---snip---
===============================================================================
BGP IPv6 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::168:25:2
Path Id : None
To : 2001:db8::168:25:1
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : n/a Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : n/a
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.2
Origin : IGP
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
PE-2 receives the BGP update which CE-2 sends for the IPv6 address family:
[/]
A:admin@PE-2# show log log-id "log_2"
---snip---
6 2022/07/19 11:29:41.237 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::168:25:2
"Peer 1: 2001:db8::168:25:2: UPDATE
Peer 1: 2001:db8::168:25:2 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 55
Flag: 0x90 Type: 14 Len: 38 Multiprotocol Reachable NLRI:
Address Family IPV6
NextHop len 16 Global NextHop 2001:db8::168:25:2
2001:db8::2:5/128
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 6 AS Path:
Type: 2 Len: 1 < 64505 >
"
---snip---
Upon receipt of the BGP update from CE-2, PE-2 programs route prefix 2001:db8::2:5/128 in its route table and FIB, with the interface towards CE-2 as next hop.
Verify the resulting IPv6 route table on PE-2:
[/]
A:admin@PE-2# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
---snip---
2001:db8::2:4/128 Remote BGP 00h00m49s 170
2001:db8:aaaa:101:0:3000:: (tunneled:SRV6) 10
2001:db8::2:5/128 Remote BGP 00h10m45s 170
2001:db8::168:25:2 0
---snip---
2001:db8:aaaa:101::/64 Remote ISIS 00h03m20s 18
2001:db8:aaaa:101::/64 (tunneled:SRV6-ISIS) 10
2001:db8:aaaa:102::/64 Local SRV6 00h01m42s 3
fe80::201-"_tmnx_fpe_2.a" 0
2001:db8:aaaa:102:0:1000::/128 Local SRV6 00h01m42s 3
Black Hole 0
2001:db8:aaaa:102:0:4000::/128 Local ISIS 00h01m42s 18
fe80::60a:1ff:fe01:1-"int-PE-2-PE-1" 10
2001:db8:aaaa:102:0:5000::/128 Local ISIS 00h01m42s 18
fe80::612:1ff:fe01:b-"int-PE-2-RR-3" 10
-------------------------------------------------------------------------------
No. of Routes: 14
---snip---
===============================================================================
Verify the corresponding IPv6 BGP routes on PE-2:
[/]
A:admin@PE-2# show router bgp routes 2001:db8::2:5/128 hunt
===============================================================================
BGP Router ID:2.2.2.2 AS:64500 Local AS:64500
===============================================================================
---snip---
===============================================================================
BGP IPv6 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::168:25:2
Path Id : None
From : 2001:db8::168:25:2
Res. Protocol : LOCAL Res. Metric : 0
Res. Nexthop : 2001:db8::168:25:2
Local Pref. : None Interface Name : int-PE-2-CE-2
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.5
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : External
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h10m45s
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::2:2
Path Id : None
To : 2001:db8::2:3
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : 100 Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.3
Origin : IGP
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
SRv6 TLV Type : SRv6 L3 Service TLV (5)
SRv6 SubTLV : SRv6 SID Information (1)
Sid : 2001:db8:aaaa:102:0:3000::
Behavior : End.DT6 (18)
SRv6 SubSubTLV : SRv6 SID Structure (1)
Loc-Block-Len : 48 Loc-Node-Len : 16
Func-Len : 20 Arg-Len : 0
Tpose-Len : 0 Tpose-offset : 0
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
PE-2 then advertises route prefix 2001:db8::2:5/128, via RR-3, and inserts the SRv6 Services TLV. This TLV carries an SRv6 Service Information sub-TLV that contains the End.DT6 SID.
PE-1 receives (via RR-3) the BGP update which PE-2 sends for the IPv6 address family:
[/]
A:admin@PE-1# show log log-id "log_2"
---snip---
4 2022/07/19 11:39:38.404 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::2:3
"Peer 1: 2001:db8::2:3: UPDATE
Peer 1: 2001:db8::2:3 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 116
Flag: 0x90 Type: 14 Len: 38 Multiprotocol Reachable NLRI:
Address Family IPV6
NextHop len 16 Global NextHop 2001:db8::2:2
2001:db8::2:5/128
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 6 AS Path:
Type: 2 Len: 1 < 64505 >
Flag: 0x40 Type: 5 Len: 4 Local Preference: 100
Flag: 0x80 Type: 9 Len: 4 Originator ID: 2.2.2.2
Flag: 0x80 Type: 10 Len: 4 Cluster ID:
3.3.3.3
Flag: 0xc0 Type: 40 Len: 37 Prefix-SID-attr:
SRv6 Services TLV (37 bytes):-
Type: SRV6 L3 Service TLV (5)
Length: 34 bytes, Reserved: 0x0
SRv6 Service Information Sub-TLV (33 bytes)
Type: 1 Len: 30 Rsvd1: 0x0
SRv6 SID: 2001:db8:aaaa:102:0:3000::
SID Flags: 0x0 Endpoint Behavior: 0x12 Rsvd2: 0x0
SRv6 SID Sub-Sub-TLV
Type: 1 Len: 6
BL:48 NL:16 FL:20 AL:0 TL:0 TO:0
"
---snip---
Upon receipt of the BGP update from RR-3 on behalf of PE-2, PE-1 programs route prefix 2001:db8::2:5/128 in its route table and FIB. The presence of the SRv6 Services TLV indicates that the next hop is the SRv6 End.DT6 SID which, in turn, is resolved to the remote locator for PE-2.
PE-1 then advertises route prefix 2001:db8::2:5/128 to CE-1 (in RIB Out Entries).
Verify the resulting IPv6 route table on PE-1. The IPv6 route table has a route to the remote IPv6 system address of CE-2, now resolved to the End.DT6 SID of the remotely configured locator prefix of PE-2. The local auto-allocated SRv6 End.X functions have a renumbered SID, because their initial SID is now used for the statically configured SRv6 End.DT4 and SRv6 End.DT6 functions.
[/]
A:admin@PE-1# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
---snip---
2001:db8::2:5/128 Remote BGP 00h00m46s 170
2001:db8:aaaa:102:0:3000:: (tunneled:SRV6) 10
---snip---
2001:db8:aaaa:101::/64 Local SRV6 00h02m02s 3
fe80::201-"_tmnx_fpe_2.a" 0
2001:db8:aaaa:101:0:1000::/128 Local SRV6 00h02m02s 3
Black Hole 0
2001:db8:aaaa:101:0:4000::/128 Local ISIS 00h02m02s 18
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
2001:db8:aaaa:101:0:5000::/128 Local ISIS 00h02m02s 18
fe80::612:1ff:fe01:1-"int-PE-1-RR-3" 10
2001:db8:aaaa:102::/64 Remote ISIS 00h03m18s 18
2001:db8:aaaa:102::/64 (tunneled:SRV6-ISIS) 10
-------------------------------------------------------------------------------
No. of Routes: 14
---snip---
===============================================================================
Verify the corresponding IPv6 BGP routes on PE-1:
[/]
A:admin@PE-1# show router bgp routes 2001:db8::2:5/128 hunt
===============================================================================
BGP Router ID:2.2.2.1 AS:64500 Local AS:64500
===============================================================================
---snip---
===============================================================================
BGP IPv6 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::2:2
Path Id : None
From : 2001:db8::2:3
Res. Protocol : ISIS Res. Metric : 10
Res. Nexthop : fe80::60e:1ff:fe01:1
Local Pref. : 100 Interface Name : int-PE-1-PE-2
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 10
Connector : None
Community : No Community Members
Cluster : 3.3.3.3
Originator Id : 2.2.2.2 Peer Router Id : 2.2.2.3
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : Internal
AS-Path : 64505
Route Tag : 0
Neighbor-AS : 64505
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h00m46s
SRv6 TLV Type : SRv6 L3 Service TLV (5)
SRv6 SubTLV : SRv6 SID Information (1)
Sid : 2001:db8:aaaa:102:0:3000::
Behavior : End.DT6 (18)
SRv6 SubSubTLV : SRv6 SID Structure (1)
Loc-Block-Len : 48 Loc-Node-Len : 16
Func-Len : 20 Arg-Len : 0
Tpose-Len : 0 Tpose-offset : 0
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::168:14:1
Path Id : None
To : 2001:db8::168:14:2
Res. Protocol : INVALID Res. Metric : 0
Res. Nexthop : n/a
Local Pref. : n/a Interface Name : NotAvailable
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 10
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.4
Origin : IGP
AS-Path : 64500 64505
Route Tag : 0
Neighbor-AS : 64500
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
CE-1 receives the BGP update which PE-1 sends for the IPv6 address family:
[/]
A:admin@CE-1# show log log-id "log_2"
---snip---
2 2022/07/19 11:39:39.220 CEST MINOR: DEBUG #2001 Base Peer 1: 2001:db8::168:14:1
"Peer 1: 2001:db8::168:14:1: UPDATE
Peer 1: 2001:db8::168:14:1 - Received BGP UPDATE:
Withdrawn Length = 0
Total Path Attr Length = 59
Flag: 0x90 Type: 14 Len: 38 Multiprotocol Reachable NLRI:
Address Family IPV6
NextHop len 16 Global NextHop 2001:db8::168:14:1
2001:db8::2:5/128
Flag: 0x40 Type: 1 Len: 1 Origin: 0
Flag: 0x40 Type: 2 Len: 10 AS Path:
Type: 2 Len: 2 < 64500 64505 >
"
---snip---
Upon receipt of the BGP update from PE-1, CE-1 programs prefix 2001:db8::2:5/128 in its route table and FIB, with the interface towards PE-1 as next hop.
Verify the resulting IPv6 route table on CE-1:
[/]
A:admin@CE-1# show router route-table ipv6
===============================================================================
IPv6 Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
2001:db8::2:4/128 Local Local 00h15m40s 0
system 0
2001:db8::2:5/128 Remote BGP 00h00m51s 170
2001:db8::168:14:1 0
2001:db8::168:14:0/126 Local Local 00h15m39s 0
int-CE-1-PE-1 0
-------------------------------------------------------------------------------
No. of Routes: 3
---snip---
===============================================================================
Verify the corresponding IPv6 BGP routes on CE-1:
[/]
A:admin@CE-1# show router bgp routes 2001:db8::2:5/128 hunt
===============================================================================
BGP Router ID:2.2.2.4 AS:64504 Local AS:64504
===============================================================================
---snip---
===============================================================================
BGP IPv6 Routes
===============================================================================
-------------------------------------------------------------------------------
RIB In Entries
-------------------------------------------------------------------------------
Network : 2001:db8::2:5/128
Nexthop : 2001:db8::168:14:1
Path Id : None
From : 2001:db8::168:14:1
Res. Protocol : LOCAL Res. Metric : 0
Res. Nexthop : 2001:db8::168:14:1
Local Pref. : None Interface Name : int-CE-1-PE-1
Aggregator AS : None Aggregator : None
Atomic Aggr. : Not Atomic MED : None
AIGP Metric : None IGP Cost : 0
Connector : None
Community : No Community Members
Cluster : No Cluster Members
Originator Id : None Peer Router Id : 2.2.2.1
Fwd Class : None Priority : None
Flags : Used Valid Best IGP In-RTM
Route Source : External
AS-Path : 64500 64505
Route Tag : 0
Neighbor-AS : 64500
Orig Validation: NotFound
Source Class : 0 Dest Class : 0
Add Paths Send : Default
RIB Priority : Normal
Last Modified : 00h00m51s
-------------------------------------------------------------------------------
RIB Out Entries
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
Verify the SRv6 local SIDs on PE-2 and similar on PE-1. The SRv6 local SIDs 2001:db8:aaaa:102:0:2000:: and 2001:db8:aaaa:102:0:3000:: now correspond with the additional SRv6 End.DT4 and SRv6 End.DT6 behavior that is configured on the locator for the data transport between CE-1 and CE-2. RR-3, CE-1, and CE-2 do not have SRv6 configuration and do not have SRv6 local SIDs.
[/]
A:admin@PE-2# show router segment-routing-v6 local-sid
===============================================================================
Segment Routing v6 Local SIDs
===============================================================================
SID Type Function
Locator
Context
-------------------------------------------------------------------------------
2001:db8:aaaa:102:0:1000:: End 1
PE-2_loc
Base
2001:db8:aaaa:102:0:2000:: End.DT4 2
PE-2_loc
Base
2001:db8:aaaa:102:0:3000:: End.DT6 3
PE-2_loc
Base
2001:db8:aaaa:102:0:4000:: End.X 4
PE-2_loc
None
2001:db8:aaaa:102:0:5000:: End.X 5
PE-2_loc
None
-------------------------------------------------------------------------------
SIDs : 5
-------------------------------------------------------------------------------
===============================================================================
Verify the SRv6 base routing instance on PE-2 and similar on PE-1.
[/]
A:admin@PE-2# show router segment-routing-v6 base-routing-instance
===============================================================================
Segment Routing v6 Base Routing Instance
===============================================================================
Locator
Type Function SID Status/InstId
SRH-mode Protection Interface
-------------------------------------------------------------------------------
PE-2_loc
End.DT4 2 2001:db8:aaaa:102:0:2000:: ok
End.DT6 3 2001:db8:aaaa:102:0:3000:: ok
End 1 2001:db8:aaaa:102:0:1000:: ok
USP
-------------------------------------------------------------------------------
Auto-allocated End.X: PSP Unprotected,
-------------------------------------------------------------------------------
End.X *4 2001:db8:aaaa:102:0:4000:: 0
PSP Unprotected int-PE-2-PE-1
ISIS Level: L2 Mac Address: 04:0a:01:01:00:01 Nbr Sys Id: 0010.0100.1001
End.X *5 2001:db8:aaaa:102:0:5000:: 0
PSP Unprotected int-PE-2-RR-3
ISIS Level: L2 Mac Address: 04:12:01:01:00:0b Nbr Sys Id: 0010.0100.1003
-------------------------------------------------------------------------------
===============================================================================
Legend: * - System allocated
Verify that the tunnel from PE-1 to the remote locator has SRv6 encapsulation and similar for the tunnel from PE-2 to the remote locator. The tunnel tables on RR-3 and on CE-1 are empty.
[/]
A:admin@PE-1# show router tunnel-table ipv6
===============================================================================
IPv6 Tunnel Table (Router: Base)
===============================================================================
Destination Owner Encap TunnelId Pref
Nexthop Color Metric
-------------------------------------------------------------------------------
2001:db8:aaaa:102::/64 srv6-isis SRV6 524289 0
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 10
-------------------------------------------------------------------------------
---snip---
===============================================================================
Verify that the tunnel from PE-1 to the remote locator uses the “int-PE-1-PE-2” interface and similar for the tunnel from PE-2 to the remote locator, where that tunnel uses the “int-PE-2-PE-1” interface. Interface “int-PE-1-PE-2” is configured on port 1/1/c1/1:1000. The FP tunnel tables on RR-3 and on CE-1 are empty.
[/]
A:admin@PE-1# show router fp-tunnel-table 1 ipv6
===============================================================================
IPv6 Tunnel Table Display
Legend:
label stack is ordered from bottom-most to top-most
B - FRR Backup
===============================================================================
Destination Protocol Tunnel-ID
Lbl/SID
NextHop Intf/Tunnel
Lbl/SID (backup)
NextHop (backup)
-------------------------------------------------------------------------------
2001:db8:aaaa:102::/64 SRV6 524289
-
fe80::60e:1ff:fe01:1-"int-PE-1-PE-2" 1/1/c1/1:1000
-------------------------------------------------------------------------------
Total Entries : 1
-------------------------------------------------------------------------------
===============================================================================
Verify that data transport is possible between CE-1 and CE-2. IPv4 data flows from CE-1 to PE-1, where it is SRv6-encapsulated and forwarded via the SRv6 tunnel to PE-2. At PE-2, the data is decapsulated and is forwarded to CE-2. Between PE-1 and PE-2, the IPv4 data cannot flow unencapsulated because there is no IPv4 interface between PE-1 and PE-2.
[/]
A:admin@CE-1# ping 192.0.2.5
PING 192.0.2.5 56 data bytes
64 bytes from 192.0.2.5: icmp_seq=1 ttl=62 time=2.13ms.
---snip---
---- 192.0.2.5 PING Statistics ----
5 packets transmitted, 5 packets received, 0.00% packet loss
round-trip min = 1.76ms, avg = 1.98ms, max = 2.35ms, stddev = 0.225ms
[/]
A:admin@CE-1# traceroute 192.0.2.5
traceroute to 192.0.2.5, 30 hops max, 40 byte packets
1 172.16.14.1 (172.16.14.1) 0.783 ms 0.864 ms 0.893 ms
2 0.0.0.0 * * *
3 192.0.2.5 (192.0.2.5) 2.07 ms 1.83 ms 1.87 ms
IPv6 data flows from CE-1 to PE-1, where it is SRv6 encapsulated and forwarded via the SRv6 tunnel to PE-2. At PE-2, the data is decapsulated and is forwarded to CE-2. The IPv6 data does not flow with native IPv6 between PE-1 and PE-2 because then it would use the 2001:db8::168:12:1 IPv6 interface instead of the 2001:db8::2:2 IPv6 system address in the second hop. The same is true for data transport between CE-2 and CE-1.
[/]
A:admin@CE-1# ping 2001:db8::2:5
PING 2001:db8::2:5 56 data bytes
64 bytes from 2001:db8::2:5 icmp_seq=1 hlim=62 time=1.68ms.
---snip---
---- 2001:db8::2:5 PING Statistics ----
5 packets transmitted, 5 packets received, 0.00% packet loss
round-trip min = 1.68ms, avg = 1.75ms, max = 1.83ms, stddev = 0.056ms
[/]
A:admin@CE-1# traceroute 2001:db8::2:5
traceroute to 2001:db8::2:5, 30 hops max, 60 byte packets
1 2001:db8::168:14:1 (2001:db8::168:14:1) 0.835 ms 0.915 ms 0.809 ms
2 2001:db8::2:2 (2001:db8::2:2) 1.54 ms 1.59 ms 1.51 ms
3 2001:db8::2:5 (2001:db8::2:5) 1.88 ms 1.73 ms 2.00 ms
Conclusion
SRv6 Encapsulation in the base routing instance can be used to transport native IPv4 and IPv6 data across an SRv6-enabled provider network.