Advertising IPv4 NLRI with IPv6 Next-Hop
This chapter describes Advertising IPv4 NLRI with IPv6 Next-Hop.
Topics in this chapter include:
Applicability
The information and configuration in this chapter are based on SR OS Release 24.3.R1. Advertising IPv4 Network Layer Reachability Information (NLRI) with IPv6 next-hop is supported in SR OS Release 19.5.R1 and later.
Overview
In networks where the routers are interconnected by IPv6-only links, SR OS routers can advertise and receive BGP routes that convey reachability to IPv4-unicast destinations that are reachable through IPv6 next-hops. Advertising and receiving IPv4 routes with IPv6 next-hops is useful in networks or regions with IPv6-only interfaces, such as data center deployments where leaf, spine, and aggregation routers are interconnected by IPv6-only links that carry a mix of unencapsulated IPv4 and IPv6 packets.
This feature requires the Extended Next Hop encoding BGP capability which is described in RFC 5549, Advertising IPv4 Network Layer Reachability Information with an IPv6 Next Hop. BGP capabilities are advertised between peers. For the Extended Next Hop encoding capability, the capability code field must be set to 5, the capability length field set to the length of the capability value field, and a capability value field with the format shown in Capability value field format:
Each triplet (NLRI AFI, NLRI SAFI, Nexthop AFI) indicates that NLRI AFI/SAFI may be advertised with a next-hop address belonging to the network-layer protocol of "Nexthop AFI".
By default, IPv4-unicast routes are advertised with IPv4 next-hops. However, on IPv6-only TCP transport sessions, IPv4-unicast routes can be advertised with IPv6 next-hops if the advertise-ipv6-next-hops command with the ipv4 true option applies to the session. The advertise-ipv6-next-hops command can be enabled for several address families, as follows:
# on PE-1:
configure {
router "Base" {
bgp {
advertise-ipv6-next-hops ?
advertise-ipv6-next-hops
evpn - Advertise EVPN route with IPv6 next-hop address
ipv4 - Advertise IPv4 route with IPv6 next-hop address
label-ipv4 - Advertise label IPv4 route with IPv6 next-hop address
label-ipv6 - Advertise label IPv6 route with IPv6 next-hop address
vpn-ipv4 - Advertise VPN IPv4 route with IPv6 next-hop address
vpn-ipv6 - Advertise VPN IPv6 route with IPv6 next-hop addressFor receiving IPv4-unicast routes with IPv6 next-hop addresses, the extended-nh-encoding command with the ipv4 true option must be applied to the session. This advertises the RFC 5549 capability to the peer for the different address families. The extended-nh-encoding command can be configured for several address families, as follows:
# on PE-1:
configure {
router "Base" {
bgp {
extended-nh-encoding ?
extended-nh-encoding
ipv4 - Advertise encoding capability for IPv4 routes
label-ipv4 - Advertise encoding capability for label-IPv4 routes
vpn-ipv4 - Advertise encoding capability for VPN-IPv4 routesWhen the BGP session is established, the BGP peers advertise the capability to each other, and the Extended Next Hop encoding capability is both a local and a remote capability, as in the following example between BGP peers 2001:db8::12:1 and 2001:db8::12:2:
[/]
A:admin@PE-1# show router bgp neighbor "2001:db8::12:2" | match "Capability" post-lines 1
Local Capability : RtRefresh MPBGP 4byte ASN ExtNhEncoding
Remote Capability : RtRefresh MPBGP 4byte ASN ExtNhEncoding
---snip---When next-hop-self true applies to the BGP session and the neighbor address is IPv6, an IPv4-unicast route that is advertised or re-advertised gets the following as next-hop:
The IPv6 local address used for peering, if the peer opened the BGP session by advertising an extended next-hop encoding capability with NLRI AFI=1, SAFI=1, and nexthop AFI=2, and the session is associated with an advertise-ipv6-next-hops ipv4 true command.
The IPv4 system interface address in all other cases.
Configuration
Example topology with IPv6 interfaces shows the example topology with three nodes with IPv6-only interfaces in different Autonomous Systems (ASs).
The initial configuration includes:
Cards, MDAs, ports
Router interfaces with IPv6 addresses
In the example, IPv4, label-IPv4, and VPN-IPv4 routes are advertised with an IPv6 next-hop. On PE-1, loopback interfaces lo1 (10.1.0.1/32) and lo2 (10.131.0.1/32) are configured; lo1 is advertised as an IPv4 route and lo2 as a label-IPv4 route. VPRN 1 is configured on all nodes with loopback interface lo3, and prefix 172.31.0.1/32 is advertised as a VPN-IPv4 route on PE-1. PE-2 and PE-3 have similar loopback interfaces. Loopback addresses and advertised IPv4, label-IPv4, and VPN-IPv4 routes shows the loopback addresses and the advertised routes.
On PE-2, the interface configuration is as follows:
# on PE-2:
configure {
router "Base" {
interface "int-PE-2-PE-1" {
port 1/1/c2/1
ipv6 {
address 2001:db8::12:2 {
prefix-length 126
}
}
}
interface "int-PE-2-PE-3-0" {
port 1/1/c1/1
ipv6 {
address 2001:db8::23:1 {
prefix-length 126
}
}
}
interface "int-PE-2-PE-3-4" {
port 1/1/c3/1
ipv6 {
address 2001:db8::23:5 {
prefix-length 126
}
}
}
interface "lo1" {
loopback
ipv4 {
primary {
address 10.2.0.1
prefix-length 32
}
}
ipv6 {
address 2001:db8::10:2:0:1 {
prefix-length 128
}
}
}
interface "lo2" {
loopback
ipv4 {
primary {
address 10.132.0.1
prefix-length 32
}
}
ipv6 {
address 2001:db8::10:132:0:1 {
prefix-length 128
}
}
}
interface "system" {
ipv4 {
primary {
address 192.0.2.2
prefix-length 32
}
}
ipv6 {
address 2001:db8::2:2 {
prefix-length 128
}
}
}
}
}# on PE-2:
configure {
service {
vprn "VPRN 1" {
admin-state enable
service-id 1
customer "1"
ecmp 2
bgp-ipvpn {
mpls {
admin-state enable
route-distinguisher "64502:1"
vrf-target {
community "target:1:1"
}
auto-bind-tunnel {
resolution filter
}
}
}
interface "lo3" {
loopback true
ipv4 {
primary {
address 172.31.0.2
prefix-length 32
}
}
ipv6 {
address 2001:db8::172:31:0:2 {
prefix-length 128
}
}
}
}
}
}The VPRN configuration on PE-1 and on PE-3 is similar.
On PE-2, eBGP is configured toward three IPv6 neighbors with next-hop-self true enabled. For each of the BGP neighbors, extended-nh-encoding and advertise-ipv6-next-hops are configured for different address families. The BGP configuration is as follows:
# on PE-2:
configure {
router "Base" {
autonomous-system 64502
ecmp 2
bgp {
inter-as-vpn true
ebgp-default-reject-policy {
import false
export false
}
multipath {
max-paths 2
ebgp 2
}
group "eBGP-IPv6" {
loop-detect discard-route
next-hop-self true
split-horizon true
family {
ipv4 true
vpn-ipv4 true
ipv6 true
vpn-ipv6 true
label-ipv4 true
label-ipv6 true
}
local-as {
as-number 64502
}
import {
policy ["import-1:1-3:3"]
}
export {
policy ["export-10.2" "export-10.132"]
}
extended-nh-encoding {
vpn-ipv4 true
label-ipv4 true
ipv4 true
}
advertise-ipv6-next-hops {
vpn-ipv6 true
label-ipv6 true
vpn-ipv4 true
label-ipv4 true
ipv4 true
}
}
neighbor "2001:db8::12:1" {
group "eBGP-IPv6"
peer-as 64501
}
neighbor "2001:db8::23:2" {
group "eBGP-IPv6"
peer-as 64503
}
neighbor "2001:db8::23:6" {
group "eBGP-IPv6"
peer-as 64503
}
}
}
}where configurations that apply for all neighbors are moved to the BGP group to which they belong. The BGP configuration on PE-1 and on PE-3 is similar.
# on PE-2:
configure {
policy-options {
community "1:1" {
member "1:1" { }
}
community "2:2" {
member "2:2" { }
}
community "3:3" {
member "3:3" { }
}
prefix-list "10.2.0.0/16" {
prefix 10.2.0.0/16 type longer { }
}
prefix-list "10.132.0.0/16" {
prefix 10.132.0.0/16 type longer { }
}
prefix-list "2001:db8::10:2:0:0/96" {
prefix 2001:db8::10:2:0:0/96 type longer { }
}
prefix-list "2001:db8::10:132:0:0/96" {
prefix 2001:db8::10:132:0:0/96 type longer { }
}
policy-statement "export-10.2" {
entry 10 {
from {
prefix-list ["10.2.0.0/16"]
}
to {
protocol {
name [bgp]
}
}
action {
action-type accept
community {
add ["2:2"]
}
}
}
entry 20 {
from {
prefix-list ["2001:db8::10:2:0:0/96"]
}
to {
protocol {
name [bgp]
}
}
action {
action-type accept
community {
add ["2:2"]
}
}
}
}
policy-statement "export-10.132" {
entry 10 {
from {
prefix-list ["10.132.0.0/16"]
}
to {
protocol {
name [bgp-label]
}
}
action {
action-type accept
community {
add ["2:2"]
}
}
}
entry 20 {
from {
prefix-list ["2001:db8::10:132:0:0/96"]
}
to {
protocol {
name [bgp-label]
}
}
action {
action-type accept
community {
add ["2:2"]
}
}
}
}
policy-statement "import-1:1-3:3" {
entry 10 {
from {
community {
name "1:1"
}
}
action {
action-type accept
}
}
entry 20 {
from {
community {
name "3:3"
}
}
action {
action-type accept
}
}
}
}
}The policies on PE-1 and on PE-3 are similar.
The BGP summary on PE-1 shows that for each of the configured address families, one route is advertised and two routes are received and accepted:
[/]
A:admin@PE-1# show router bgp summary all
===============================================================================
BGP Summary
===============================================================================
Legend : D - Dynamic Neighbor
===============================================================================
Neighbor
Description
ServiceId AS PktRcvd InQ Up/Down State|Rcv/Act/Sent (Addr Family)
PktSent OutQ
-------------------------------------------------------------------------------
2001:db8::12:2
Def. Inst 64502 34 0 00h04m59s 2/2/1 (IPv4)
28 0 2/2/1 (IPv6)
2/2/1 (VpnIPv4)
2/2/1 (VpnIPv6)
2/2/1 (Lbl-IPv4)
2/2/1 (Lbl-IPv6)
-------------------------------------------------------------------------------On PE-1, the following IPv4 routes with IPv6 next-hop are received and used: route 10.2.0.1/32 originates from PE-2 and route 10.3.0.1/32 from PE-3. Both routes have next-hop 2001:db8::12:2 because next-hop-self true is enabled, as follows:
[/]
A:admin@PE-1# show router bgp routes
===============================================================================
BGP Router ID:192.0.2.1 AS:64501 Local AS:64501
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
l - leaked, x - stale, > - best, b - backup, p - purge
Origin codes : i - IGP, e - EGP, ? - incomplete
===============================================================================
BGP IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop (Router) Path-Id IGP Cost
As-Path Label
-------------------------------------------------------------------------------
u*>i 10.2.0.1/32 None None
2001:db8::12:2 None 0
64502 -
u*>i 10.3.0.1/32 None None
2001:db8::12:2 None 0
64502 64503 -
-------------------------------------------------------------------------------
Routes : 2
===============================================================================On PE-2, the following VPN-IPv4 routes with different IPv6 next-hops are received and used:
[/]
A:admin@PE-2# show router bgp routes vpn-ipv4
===============================================================================
BGP Router ID:192.0.2.2 AS:64502 Local AS:64502
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
l - leaked, x - stale, > - best, b - backup, p - purge
Origin codes : i - IGP, e - EGP, ? - incomplete
===============================================================================
BGP VPN-IPv4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop (Router) Path-Id IGP Cost
As-Path Label
-------------------------------------------------------------------------------
u*>i 64501:1:172.31.0.1/32 None None
2001:db8::12:1 None 0
64501 524283
u*>i 64503:1:172.31.0.3/32 None None
2001:db8::23:2 None 0
64503 524281
u*>i 64503:1:172.31.0.3/32 None None
2001:db8::23:6 None 0
64503 524281
-------------------------------------------------------------------------------
Routes : 3
===============================================================================On PE-3, the following label-IPv4 routes with IPv6 next-hop are received and used. Route 10.131.0.1/32 originates from PE-1 and is re-advertised by PE-2 on two eBGP paths, with next-hop addresses 2001:db8::23:1 and 2001:db8::23:5. Route 10.132.0.1/32 originates from PE-2 and is also advertised over these two eBGP paths.
[/]
A:admin@PE-3# show router bgp routes label-ipv4
===============================================================================
BGP Router ID:192.0.2.3 AS:64503 Local AS:64503
===============================================================================
Legend -
Status codes : u - used, s - suppressed, h - history, d - decayed, * - valid
l - leaked, x - stale, > - best, b - backup, p - purge
Origin codes : i - IGP, e - EGP, ? - incomplete
===============================================================================
BGP LABEL-IPV4 Routes
===============================================================================
Flag Network LocalPref MED
Nexthop (Router) Path-Id IGP Cost
As-Path Label
-------------------------------------------------------------------------------
u*>i 10.131.0.1/32 None None
2001:db8::23:1 None 0
64502 64501 524286
u*>i 10.131.0.1/32 None None
2001:db8::23:5 None 0
64502 64501 524286
u*>i 10.132.0.1/32 None None
2001:db8::23:1 None 0
64502 524287
u*>i 10.132.0.1/32 None None
2001:db8::23:5 None 0
64502 524287
-------------------------------------------------------------------------------
Routes : 4
===============================================================================The route table on PE-3 includes BGP IPv4 and label-IPv4 routes with IPv6 next-hops, as follows:
[/]
A:admin@PE-3# show router route-table
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
10.1.0.1/32 Remote BGP 00h07m07s 170
2001:db8::23:1 0
10.1.0.1/32 Remote BGP 00h07m07s 170
2001:db8::23:5 0
10.2.0.1/32 Remote BGP 00h07m07s 170
2001:db8::23:1 0
10.2.0.1/32 Remote BGP 00h07m07s 170
2001:db8::23:5 0
10.3.0.1/32 Local Local 00h15m16s 0
lo1 0
10.131.0.1/32 Remote BGP_LABEL 00h07m07s 170
2001:db8::23:1 0
10.131.0.1/32 Remote BGP_LABEL 00h07m07s 170
2001:db8::23:5 0
10.132.0.1/32 Remote BGP_LABEL 00h07m07s 170
2001:db8::23:1 0
10.132.0.1/32 Remote BGP_LABEL 00h07m07s 170
2001:db8::23:5 0
10.133.0.1/32 Local Local 00h15m16s 0
lo2 0
192.0.2.3/32 Local Local 00h15m16s 0
system 0
-------------------------------------------------------------------------------
No. of Routes: 11
---snip---
===============================================================================The tunnel table on PE-3 shows four BGP tunnels with IPv6 next-hops, as follows:
[/]
A:admin@PE-3# show router tunnel-table
===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination Owner Encap TunnelId Pref Nexthop Metric
Color
-------------------------------------------------------------------------------
10.131.0.1/32 bgp MPLS 262146 12 2001:db8::23:1 1000
10.131.0.1/32 bgp MPLS 262146 12 2001:db8::23:5 1000
10.132.0.1/32 bgp MPLS 262145 12 2001:db8::23:1 1000
10.132.0.1/32 bgp MPLS 262145 12 2001:db8::23:5 1000
-------------------------------------------------------------------------------
---snip---
===============================================================================The route table for VPRN 1 on PE-3 includes BGP VPN-IPv4 routes with IPv6 next-hops, as follows:
[/]
A:admin@PE-3# show router "1" route-table
===============================================================================
Route Table (Service: 1)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
172.31.0.1/32 Remote BGP VPN 00h05m28s 170
2001:db8::23:1 0
172.31.0.1/32 Remote BGP VPN 00h05m28s 170
2001:db8::23:5 0
172.31.0.2/32 Remote BGP VPN 00h05m28s 170
2001:db8::23:1 0
172.31.0.2/32 Remote BGP VPN 00h05m28s 170
2001:db8::23:5 0
172.31.0.3/32 Local Local 00h05m32s 0
lo3 0
-------------------------------------------------------------------------------
No. of Routes: 5
---snip---
===============================================================================The reachability between source address 172.31.0.3 and destination 172.31.0.1 can be verified, but the following traceroute does not display any address for the intermediate node:
[/]
A:admin@PE-3# traceroute 172.31.0.1 router-instance "VPRN 1" numeric source-address 172.31.0.3
traceroute to 172.31.0.1 from 172.31.0.3, 30 hops max, 40 byte packets
1 0.0.0.0 * * *
2 172.31.0.1 3.42 ms 3.29 ms 3.62 msHowever, the following traceroute from lo1 on PE-3 to lo1 on PE-1 fails:
[/]
A:admin@PE-3# traceroute 10.1.0.1 numeric source-address 10.3.0.1
traceroute to 10.1.0.1 from 10.3.0.1, 30 hops max, 40 byte packets
1 0.0.0.0 * * *
2 0.0.0.0 * * *
3 0.0.0.0 * * *
4 0.0.0.0 * * *
5 0.0.0.0 * * *
6 0.0.0.0 * ^C
traceroute aborted by userIn an IPv6-only network, the IPv4 interfaces are down, as follows:
[/]
A:admin@PE-2# show router interface
===============================================================================
Interface Table (Router: Base)
===============================================================================
Interface-Name Adm Opr(v4/v6) Mode Port/SapId
IP-Address PfxState
-------------------------------------------------------------------------------
int-PE-2-PE-1 Up Down/Up Network 1/1/c2/1
2001:db8::12:2/126 PREFERRED
fe80::60e:1ff:fe01:b/64 PREFERRED
int-PE-2-PE-3-0 Up Down/Up Network 1/1/c1/1
2001:db8::23:1/126 PREFERRED
fe80::60e:1ff:fe01:1/64 PREFERRED
int-PE-2-PE-3-4 Up Down/Up Network 1/1/c3/1
2001:db8::23:5/126 PREFERRED
fe80::60e:1ff:fe01:15/64 PREFERRED
lo1 Up Up/Up Network loopback
10.2.0.1/32 n/a
2001:db8::10:2:0:1/128 PREFERRED
fe80::202:feff:fe00:0/64 PREFERRED
lo2 Up Up/Up Network loopback
10.132.0.1/32 n/a
2001:db8::10:132:0:1/128 PREFERRED
fe80::202:feff:fe00:0/64 PREFERRED
system Up Up/Up Network system
192.0.2.2/32 n/a
2001:db8::2:2/128 PREFERRED
-------------------------------------------------------------------------------
Interfaces : 6
===============================================================================To allow CPM-originated or terminated packets, such as IPv4 ping or traceroute traffic, the forward-ipv4-packets command is configured in the ipv6 context of these interfaces, as follows:
# on PE-2:
configure {
router "Base" {
interface "int-PE-2-PE-1" {
ipv6 {
forward-ipv4-packets true
}
}
interface "int-PE-2-PE-3-0" {
ipv6 {
forward-ipv4-packets true
}
}
interface "int-PE-2-PE-3-4" {
ipv6 {
forward-ipv4-packets true
}
}
}
}The configuration on PE-1 and on PE-3 is similar.
The connectivity between the lo1 and lo2 interfaces can now be verified from PE-3, as follows:
[/]
A:admin@PE-3# traceroute 10.1.0.1 numeric source-address 10.3.0.1
traceroute to 10.1.0.1 from 10.3.0.1, 30 hops max, 40 byte packets
1 10.2.0.1 2.36 ms 2.81 ms 2.94 ms
2 10.1.0.1 3.97 ms 3.45 ms 3.65 ms[/]
A:admin@PE-3# traceroute 10.2.0.1 numeric source-address 10.3.0.1
traceroute to 10.2.0.1 from 10.3.0.1, 30 hops max, 40 byte packets
1 10.2.0.1 2.57 ms 2.98 ms 3.02 ms[/]
A:admin@PE-3# traceroute 10.131.0.1 numeric source-address 10.133.0.1
traceroute to 10.131.0.1 from 10.133.0.1, 30 hops max, 40 byte packets
1 10.2.0.1 2.56 ms 2.67 ms 2.86 ms
2 10.131.0.1 3.70 ms 3.85 ms 3.60 ms[/]
A:admin@PE-3# traceroute 10.132.0.1 numeric source-address 10.133.0.1
traceroute to 10.132.0.1 from 10.133.0.1, 30 hops max, 40 byte packets
1 10.132.0.1 2.37 ms 2.93 ms 6.76 msWith the forward-ipv4-packets command, the IOM is instructed by the CPM to consider the IPv4 operational state of the interface as up when the IPv6 interface is operationally up. IPv4 packets can be sent and received on the interface when the IPv6 interface is up, even when the IPv4 interface is operationally down.
[/]
A:admin@PE-1# show router bgp neighbor "2001:db8::12:2" | match "Capability" post-lines 1
Local Capability : RtRefresh MPBGP 4byte ASN
Remote Capability : RtRefresh MPBGP 4byte ASN ExtNhEncoding
---snip---
[/]
A:admin@PE-2# show router bgp neighbor "2001:db8::12:1" | match "Capability" post-lines 1
Local Capability : RtRefresh MPBGP 4byte ASN ExtNhEncoding
Remote Capability : RtRefresh MPBGP 4byte ASN
---snip---[/]
A:admin@PE-1# show router bgp summary all
===============================================================================
BGP Summary
===============================================================================
Legend : D - Dynamic Neighbor
===============================================================================
Neighbor
Description
ServiceId AS PktRcvd InQ Up/Down State|Rcv/Act/Sent (Addr Family)
PktSent OutQ
-------------------------------------------------------------------------------
2001:db8::12:2
Def. Inst 64502 24 0 00h01m44s 2/0/1 (IPv4)
18 0 2/2/1 (IPv6)
2/0/1 (VpnIPv4)
2/2/1 (VpnIPv6)
2/0/1 (Lbl-IPv4)
2/2/1 (Lbl-IPv6)
-------------------------------------------------------------------------------- When overextending true is configured on PE-1:
- the PE-1 route table has BGP routes to lo1 on PE-2, lo1 on PE-3, lo2
on PE-2, and lo2 on PE-3, via an IPv6 next-hop as
follows:
[/] 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 ------------------------------------------------------------------------------- 10.1.0.1/32 Local Local 00h15m41s 0 lo1 0 10.2.0.1/32 Remote BGP 00h07m12s 170 2001:db8::12:2 0 10.3.0.1/32 Remote BGP 00h06m43s 170 2001:db8::12:2 0 10.131.0.1/32 Local Local 00h15m41s 0 lo2 0 10.132.0.1/32 Remote BGP_LABEL 00h07m12s 170 2001:db8::12:2 0 10.133.0.1/32 Remote BGP_LABEL 00h06m43s 170 2001:db8::12:2 0 192.0.2.1/32 Local Local 00h15m41s 0 system 0 ------------------------------------------------------------------------------- No. of Routes: 7 ---snip--- =============================================================================== - the VPRN 1 route table on PE-1 has BGP routes to lo3 on PE-2 and lo3
on PE-3, via an IPv6 next-hop as
follows:
[/] A:admin@PE-1# show router "1" route-table ipv4 =============================================================================== Route Table (Service: 1) =============================================================================== Dest Prefix[Flags] Type Proto Age Pref Next Hop[Interface Name] Metric ------------------------------------------------------------------------------- 172.31.0.1/32 Local Local 00h05m54s 0 lo3 0 172.31.0.2/32 Remote BGP VPN 00h05m33s 170 2001:db8::12:2 0 172.31.0.3/32 Remote BGP VPN 00h04m34s 170 2001:db8::12:2 0 ------------------------------------------------------------------------------- No. of Routes: 3 ---snip--- =============================================================================== - the tunnel table on PE-1 has tunnels to lo2 on PE-2 and lo2 on PE-3,
as follows:
[/] A:admin@PE-1# show router tunnel-table =============================================================================== IPv4 Tunnel Table (Router: Base) =============================================================================== Destination Owner Encap TunnelId Pref Nexthop Metric Color ------------------------------------------------------------------------------- 10.132.0.1/32 bgp MPLS 262145 12 2001:db8::12:2 1000 10.133.0.1/32 bgp MPLS 262146 12 2001:db8::12:2 1000 ------------------------------------------------------------------------------- ---snip--- ===============================================================================
- the PE-1 route table has BGP routes to lo1 on PE-2, lo1 on PE-3, lo2
on PE-2, and lo2 on PE-3, via an IPv6 next-hop as
follows:
- When extended-nh-encoding is not configured on PE-1:
- those BGP routes and tunnels are missing, as
follows:
[/] 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 ------------------------------------------------------------------------------- 10.1.0.1/32 Local Local 00h30m32s 0 lo1 0 10.131.0.1/32 Local Local 00h30m32s 0 lo2 0 192.0.2.1/32 Local Local 00h30m32s 0 system 0 ------------------------------------------------------------------------------- No. of Routes: 3 ---snip--- ===============================================================================[/] A:admin@PE-1# show router "1" route-table ipv4 =============================================================================== Route Table (Service: 1) =============================================================================== Dest Prefix[Flags] Type Proto Age Pref Next Hop[Interface Name] Metric ------------------------------------------------------------------------------- 172.31.0.1/32 Local Local 00h20m21s 0 lo3 0 ------------------------------------------------------------------------------- No. of Routes: 1 ---snip--- ===============================================================================[/] A:admin@PE-1# show router tunnel-table =============================================================================== IPv4 Tunnel Table (Router: Base) =============================================================================== Destination Owner Encap TunnelId Pref Nexthop Metric Color ------------------------------------------------------------------------------- No Matching Entries. ------------------------------------------------------------------------------- ---snip--- =============================================================================== - and there is no connectivity from and to PE-1. This is verified as
follows:
# on PE-1, towards PE-2 and PE-3 [/] A:admin@PE-1# ping 10.2.0.1 source-address 10.1.0.1 count 5 PING 10.2.0.1 56 data bytes ---snip--- ---- 10.2.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss [/] A:admin@PE-1# ping 10.3.0.1 source-address 10.1.0.1 count 5 PING 10.3.0.1 56 data bytes ---snip--- ---- 10.3.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss [/] A:admin@PE-1# ping 10.132.0.1 source-address 10.131.0.1 count 5 PING 10.132.0.1 56 data bytes ---snip--- ---- 10.132.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss [/] A:admin@PE-1# ping 10.133.0.1 source-address 10.131.0.1 count 5 PING 10.133.0.1 56 data bytes ---snip--- ---- 10.133.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss [/] A:admin@PE-1# ping 172.31.0.2 router-instance "VPRN 1" source-address 172.31.0.1 count 5 PING 172.31.0.2 56 data bytes ---snip--- ---- 172.31.0.2 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss [/] A:admin@PE-1# ping 172.31.0.3 router-instance "VPRN 1" source-address 172.31.0.1 count 5 PING 172.31.0.3 56 data bytes ---snip--- ---- 172.31.0.3 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss# on PE-3, towards PE-1 (similar on PE-2 towards PE-1): [/] A:admin@PE-3# ping 10.1.0.1 source-address 10.3.0.1 count 5 PING 10.1.0.1 56 data bytes ---snip--- ---- 10.1.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss ---snip--- [/] A:admin@PE-3# ping 10.131.0.1 source-address 10.133.0.1 count 5 PING 10.131.0.1 56 data bytes ---snip--- ---- 10.131.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss ---snip--- [/] A:admin@PE-3# ping 172.31.0.1 router-instance "VPRN 1" source-address 172.31.0.3 count 5 PING 172.31.0.1 56 data bytes ---snip--- ---- 172.31.0.1 PING Statistics ---- 5 packets transmitted, 0 packets received, 100% packet loss ---snip---
- those BGP routes and tunnels are missing, as
follows:
Conclusion
SR OS routers can advertise and receive BGP routes for IPv4 destinations with IPv6 next-hops. This feature requires the Extended Next Hop encoding BGP capability in RFC 5549 and is useful in IPv6-only networks or regions.