BGP Selective Label-IPv4 Route Installation
This chapter provides information about BGP selective label-IPv4 route installation.
Topics in this chapter include:
Applicability
The information and configuration in this chapter are based on SR OS Release 23.3.R1. BGP selective label-IPv4 route installation is supported in SR OS Release 19.10.R2, and later.
Overview
Many service providers use BGP label-unicast (BGP-LU) to build network designs that connect multiple domains into unified and scalable network fabrics. However, the number of BGP-LU IPv4 routes that are distributed in the control plane can exceed the capacity of the Forwarding Information Base (FIB) and Label Forwarding Information Base (LFIB) of small access routers.
One solution is to apply import policies on the access router to limit the number of BGP-LU IPv4 routes accepted in the RIB-IN, but this is labor-intensive and prone to errors. A better solution is selective BGP-LU IPv4 route installation in the base routing instance, which addresses these issues.
When the selective-label-ipv4-install command is configured in the bgp context of the base router, BGP-LU IPv4 routes in the RIB-IN are made invalid if they are received from a base router BGP peer and not needed by any eligible service. When a BGP-LU IPv4 route is invalid in the RIB-IN, the BGP decision process prefers any valid route over this route, and the invalid BGP-LU IPv4 route is not programmed as a next-hop (primary next-hop, ECMP next-hop, or backup next-hop) of any IP route or tunnel.
The selective-label-ipv4-install command can be configured in the bgp context of the base router: in the global bgp context, the group context, or the neighbor context, as follows:
[/]
A:admin@PE-1# tree flat detail | match selective-label-ipv4-install
configure groups group <string> router <string> bgp group <string> selective-label-ipv4-install <boolean>
configure groups group <string> router <string> bgp neighbor <string | ipv4-address-with-zone | ipv4-address | ipv6-address-linklocal-with-zone | ipv6-address | ipv6-address-with-zone> selective-label-ipv4-install <boolean>
configure groups group <string> router <string> bgp selective-label-ipv4-install <boolean>
configure router <string> bgp group <string> selective-label-ipv4-install <boolean>
configure router <string> bgp neighbor <ipv4-address-with-zone | ipv4-address | ipv6-address-linklocal-with-zone | ipv6-address | ipv6-address-with-zone> selective-label-ipv4-install <boolean>
configure router <string> bgp selective-label-ipv4-install <boolean>
When a BGP-LU IPv4 route is invalid in the RIB-IN, it is marked with the flag Label-Unicast-No-Svc and the invalid route is handled as follows:
No route for the IPv4 prefix is added to the route table from the BGP-LU RIB.
No BGP tunnel for the /32 IPv4 prefix is added to the tunnel table.
No RIB-OUT is generated for the invalid BGP-LU route, so this invalid route does not trigger a label-swap (incoming label map - ILM) entry to be programmed.
Configuring the selective-label-ipv4-install command on a BGP session unconditionally invalidates all non-/32 BGP-LU IPv4 routes received on that session, because those non-/32 routes are never used to resolve service endpoints.
Selective BGP-LU installation logic by service type shows how BGP-LU IPv4 routes are handled when the selective-label-ipv4-install command is configured.
|
Service type |
Logic marks BGP label-IPv4 routes as invalid except |
|---|---|
|
L2 services with user-provisioned SDPs |
When the user-provisioned SDP has a BGP tunnel as transport and the far end matches a /32 BGP-LU IPv4 route, that route is not marked as invalid, regardless of the operational state of the SDP. |
|
L2 services with auto-created SDPs (BGP-AD, BGP-VPLS, BGP-EVPN) |
If an L2 service imports a BGP-AD, BGP-VPLS, or BGP-EVPN route, /32 BGP-LU IPv4 routes matching the BGP next-hop address of this BGP route are not marked as invalid. |
|
EVPN next-hop-self route reflector or model-B ASBR |
If the base router BGP instance is configured as a next-hop-self RR or a model-B ASBR, BGP-LU IPv4 routes matching any IPv4 address in the BGP next-hop field of a received EVPN route are not marked as invalid, regardless of whether the transport-tunnel resolution filter allows BGP tunnels. |
|
VPRN with explicitly configured SDP |
BGP-LU IPv4 routes matching the SDP far-end address are not marked as invalid, regardless of the operational state of the SDP. |
|
VPRN with auto-bind-tunnel |
If the auto-bind VPRN service imports VPN-IPv4 or VPN-IPv6 routes where the BGP next-hop matches a BGP-LU IPv4 route, that route is not marked as invalid, regardless of whether the auto-bind-tunnel resolution filter allows BGP tunnels. |
|
VPN-IP next-hop-self RR or model-B ASBR |
If the base router BGP instance is configured as a next-hop-self RR or a model-B ASBR, BGP-LU IPv4 routes matching any IPv4 address in the BGP next-hop field of a received VPN-IP route are not marked as invalid, regardless of whether the transport-tunnel resolution filter allows BGP tunnels. |
Configuration
Example topology shows the example topology with two PEs with the services that are configured.
Initial configuration
The initial configuration on the PEs includes:
Cards, MDAs, ports
Router interfaces
SR-ISIS
On PE-2, four loopback interfaces are configured in the base router context with /32 IPv4 addresses: 192.0.1.21/32, 192.0.1.22/32, 192.0.1.23/32, and 192.0.1.24/32. The list of router interfaces on PE-2 is 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 Up/Down Network 1/1/c1/2:100
192.168.12.2/30 n/a
lo1 Up Up/Down Network loopback
192.0.1.21/32 n/a
lo2 Up Up/Down Network loopback
192.0.1.22/32 n/a
lo3 Up Up/Down Network loopback
192.0.1.23/32 n/a
lo4 Up Up/Down Network loopback
192.0.1.24/32 n/a
system Up Up/Down Network system
192.0.2.2/32 n/a
-------------------------------------------------------------------------------
Interfaces : 6
===============================================================================
These prefixes are exported as BGP-LU routes and the next-hop resolution filter for label-IPv4 routes is configured with SR-ISIS. The configuration on PE-2 is as follows:
# on PE-2:
configure {
policy-options {
prefix-list "192.0.1.0/24" {
prefix 192.0.1.0/24 type range {
start-length 32
end-length 32
}
}
policy-statement "export-svc-lu-bgp" {
entry 10 {
from {
prefix-list ["192.0.1.0/24"]
}
action {
action-type accept
}
}
}
}
router "Base" {
bgp {
split-horizon true
ebgp-default-reject-policy {
import false
export false
}
next-hop-resolution {
labeled-routes {
transport-tunnel {
family label-ipv4 {
resolution-filter {
ldp false
sr-isis true
}
}
}
}
}
group "iBGPv4" {
peer-as 64500
family {
vpn-ipv4 true
label-ipv4 true
}
}
neighbor "192.0.2.1" {
group "iBGPv4"
export {
policy ["export-svc-lu-bgp"]
}
}
}
}
PE-1 receives four valid label-IPv4 routes, as follows:
[/]
A:admin@PE-1# show router bgp routes label-ipv4
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 192.0.1.21/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.22/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.23/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.24/32 100 None
192.0.2.2 None 10
No As-Path 524286
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
The tunnel table on PE-1 includes four BGP tunnels toward the loopback interfaces on PE-2:
[/]
A:admin@PE-1# show router tunnel-table protocol bgp
===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination Owner Encap TunnelId Pref Nexthop Metric
Color
-------------------------------------------------------------------------------
192.0.1.21/32 bgp MPLS 262148 12 192.0.2.2 1000
192.0.1.22/32 bgp MPLS 262147 12 192.0.2.2 1000
192.0.1.23/32 bgp MPLS 262146 12 192.0.2.2 1000
192.0.1.24/32 bgp MPLS 262145 12 192.0.2.2 1000
-------------------------------------------------------------------------------
Flags: B = BGP or MPLS backup hop available
L = Loop-Free Alternate (LFA) hop available
E = Inactive best-external BGP route
k = RIB-API or Forwarding Policy backup hop
===============================================================================
The route table on PE-1 shows four BGP-LU IPv4 routes toward the loopback interfaces on PE-2, with next-hop resolved via an SR-ISIS tunnel:
[/]
A:admin@PE-1# show router route-table protocol bgp-label
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
192.0.1.21/32 Remote BGP_LABEL 00h01m12s 170
192.0.2.2 (tunneled:SR-ISIS:524290) 10
192.0.1.22/32 Remote BGP_LABEL 00h01m12s 170
192.0.2.2 (tunneled:SR-ISIS:524290) 10
192.0.1.23/32 Remote BGP_LABEL 00h01m12s 170
192.0.2.2 (tunneled:SR-ISIS:524290) 10
192.0.1.24/32 Remote BGP_LABEL 00h01m12s 170
192.0.2.2 (tunneled:SR-ISIS:524290) 10
-------------------------------------------------------------------------------
No. of Routes: 4
Flags: n = Number of times nexthop is repeated
B = BGP backup route available
L = LFA nexthop available
S = Sticky ECMP requested
===============================================================================
The tunnel toward destination 192.0.2.2 is the following SR-ISIS tunnel:
[/]
A:admin@PE-1# show router tunnel-table 192.0.2.2
===============================================================================
IPv4 Tunnel Table (Router: Base)
===============================================================================
Destination Owner Encap TunnelId Pref Nexthop Metric
Color
-------------------------------------------------------------------------------
192.0.2.2/32 isis (0) MPLS 524290 11 192.168.12.2 10
-------------------------------------------------------------------------------
Flags: B = BGP or MPLS backup hop available
L = Loop-Free Alternate (LFA) hop available
E = Inactive best-external BGP route
k = RIB-API or Forwarding Policy backup hop
===============================================================================
In the following examples, services that use these BGP tunnels are configured .
VPRN 1 with auto-bind-tunnel
VPRN 1 in VPRN 1 uses a BGP transport tunnel with endpoint 192.0.1.21 on PE-2 uses the BGP transport tunnel between loopback interfaces "lo1" with IP address 192.0.1.11/32 on PE-1 and 192.0.1.21/32 on PE-2.
VPRN 1 is configured with an auto-bind-tunnel and the next-hop must be resolved using a BGP tunnel. On PE-2, the policy "export-VPRN1" sets the next-hop to 192.0.1.21 and adds the community "target:64500:1", which matches the vrf-target of VPRN 1.
# on PE-2:
configure {
policy-options {
community "target:64500:1" {
member "target:64500:1" { }
}
policy-statement "export-VPRN1" {
entry 10 {
action {
action-type accept
next-hop 192.0.1.21
community {
add ["target:64500:1"]
}
}
}
}
}
service {
vprn "VPRN 1" {
admin-state enable
service-id 1
customer "1"
bgp-ipvpn {
mpls {
admin-state enable
route-distinguisher "64500:1"
vrf-target {
community "target:64500:1"
}
vrf-export {
policy ["export-VPRN1"]
}
auto-bind-tunnel {
resolution filter
}
}
}
interface "lo1" {
loopback true
ipv4 {
primary {
address 172.31.1.2
prefix-length 32
}
}
}
}
}
The configuration is similar on PE-1, but the IP addresses are different.
VPRN 1 on PE-1 receives a BGP VPN-IPv4 route for prefix 172.31.1.2/32 from PE-2. The next-hop of this BGP-VPN route is 192.0.1.21:
[/]
A:admin@PE-1# show router bgp routes vpn-ipv4
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 64500:1:172.31.1.2/32 100 None
192.0.1.21 None 0
No As-Path 524285
-------------------------------------------------------------------------------
Routes : 1
===============================================================================
VPRN 1 on PE-1 uses the BGP tunnel toward 192.0.1.21/32 while the other BGP tunnels are not required on PE-1. When BGP is configured with the selective-label-ipv4-install command, only the BGP-LU IPv4 route for 192.0.1.21/32 remains valid. The command can be configured in the global BGP context (as in the following configuration), per group, or per neighbor:
# on PE-1:
configure {
router "Base" {
bgp {
selective-label-ipv4-install true
}
From the four BGP transport tunnels on PE-1, only the BGP tunnel with endpoint 192.0.1.21/32 is used by a service, so it remains valid, as follows:
[/]
A:admin@PE-1# show router bgp routes label-ipv4
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 192.0.1.21/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.22/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.23/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.24/32 100 None
192.0.2.2 None 10
No As-Path 524286
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
The first label-IPv4 route is valid; the other three label-IPv4 routes are marked invalid with flag Label-Unicast-No-Svc:
[/]
A:admin@PE-1# show router bgp routes label-ipv4 hunt | match Flags
Flags : Used Valid Best IGP In-TTM In-RTM
Flags : Invalid IGP Label-Unicast-No-Svc
Flags : Invalid IGP Label-Unicast-No-Svc
Flags : Invalid IGP Label-Unicast-No-Svc
In the route table on PE-1, only one BGP-LU IPv4 route remains:
[/]
A:admin@PE-1# show router route-table protocol bgp-label
===============================================================================
Route Table (Router: Base)
===============================================================================
Dest Prefix[Flags] Type Proto Age Pref
Next Hop[Interface Name] Metric
-------------------------------------------------------------------------------
192.0.1.21/32 Remote BGP_LABEL 00h02m05s 170
192.0.2.2 (tunneled:SR-ISIS:524290) 10
-------------------------------------------------------------------------------
No. of Routes: 1
Flags: n = Number of times nexthop is repeated
B = BGP backup route available
L = LFA nexthop available
S = Sticky ECMP requested
===============================================================================
L2 and L3 services with user-provisioned SDP
When SDPs are configured to use a BGP transport tunnel, the corresponding BGP label-IPv4 route is not marked as invalid. The following TLDP-signaled SDP is configured with a BGP transport tunnel between the loopback interfaces "lo2" with IP address 192.0.1.12 on PE-1 and 192.0.1.22 on PE-2:
# on PE-2:
configure {
router "Base" {
ldp {
targeted-session {
peer 192.0.1.12 {
local-lsr-id {
interface-name "lo2"
}
}
}
}
}
service {
sdp 1 {
admin-state enable
delivery-type mpls
bgp-tunnel true
far-end {
ip-address 192.0.1.12
}
}
}
The configuration is similar on PE-1; only the far-end and peer address is now 192.0.1.22:
[/]
A:admin@PE-1# show service sdp
============================================================================
Services: Service Destination Points
============================================================================
SdpId AdmMTU OprMTU Far End Adm Opr Del LSP Sig
----------------------------------------------------------------------------
1 0 8970 192.0.1.22 Up Up MPLS B TLDP
----------------------------------------------------------------------------
Number of SDPs : 1
----------------------------------------------------------------------------
Legend: R = RSVP, L = LDP, B = BGP, M = MPLS-TP, n/a = Not Applicable
I = SR-ISIS, O = SR-OSPF, T = SR-TE, F = FPE
============================================================================
When an SDP uses a BGP transport tunnel, the corresponding BGP label-IPv4 route is not marked as invalid, regardless of the operational state of the SDP. The following command shows that the second BGP label-IPv4 route is now valid:
[/]
A:admin@PE-1# show router bgp routes label-ipv4
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 192.0.1.21/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.22/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.23/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.24/32 100 None
192.0.2.2 None 10
No As-Path 524286
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
This SDP can be used by L2 and L3 services. VPRN 2, VPLS 3, and Epipe 4 use user-provisioned SDP 1 with BGP tunnel shows three services that use SDP 1: VPRN 2, VPLS 3, and Epipe 4.
VPRN 2 is similar to VPRN 1, but a spoke-SDP is configured instead of the auto-bind-tunnel. The configuration is as follows:
# on PE-1:
configure {
policy-options {
community "target:64500:2" {
member "target:64500:2" { }
}
policy-statement "export-VPRN2" {
entry 10 {
action {
action-type accept
next-hop 192.0.1.12
community {
add ["target:64500:2"]
}
}
}
}
}
service {
vprn "VPRN 2" {
admin-state enable
service-id 2
customer "1"
bgp-ipvpn {
mpls {
admin-state enable
route-distinguisher "64500:2"
vrf-target {
community "target:64500:2"
}
vrf-export {
policy ["export-VPRN2"]
}
}
}
interface "lo1" {
loopback true
ipv4 {
primary {
address 172.31.2.1
prefix-length 32
}
}
}
spoke-sdp 1:2 {
}
}
}
VPLS 3 and Epipe 4 only have a spoke-SDP and a SAP, as follows:
# on PE-1:
configure {
service {
vpls "VPLS 3" {
admin-state enable
service-id 3
customer "1"
spoke-sdp 1:3 {
}
sap 1/1/c2/1:3 {
}
}
epipe "Epipe 4" {
admin-state enable
service-id 4
customer "1"
spoke-sdp 1:4 {
}
sap 1/1/c2/1:4 {
}
}
}
L2 services with auto-created SDPs
PE-1 receives BGP-VPLS and BGP-AD routes with next-hop 192.0.1.23 shows two VPLS services where the SDPs are auto-created between the loopback interfaces "lo3" on the PEs: BGP-VPLS 5 and BGP-AD VPLS 6.
For BGP-VPLS and BGP-AD, a BGP session is established for the L2-VPN address family between the loopback interfaces "lo3" on both PEs:
# on PE-2:
configure {
router "Base" {
bgp {
group "iBGP-L2" {
type internal
local-address 192.0.1.23
family {
l2-vpn true
}
}
neighbor "192.0.1.13" {
group "iBGP-L2"
}
For BGP-AD, T-LDP signaling is used, so the following T-LDP session is established:
# on PE-2:
configure {
router "Base" {
ldp {
targeted-session {
peer 192.0.1.13 {
local-lsr-id {
interface-name "lo3"
}
The service configuration is as follows:
# on PE-2:
configure {
service {
vpls "BGP-VPLS 5" {
admin-state enable
service-id 5
customer "1"
bgp 1 {
route-distinguisher "64500:5"
route-target {
export "target:64500:5"
import "target:64500:5"
}
pw-template-binding "PW1" {
import-rt ["target:64500:5"]
}
}
bgp-vpls {
admin-state enable
maximum-ve-id 100
ve {
name "PE-2"
id 2
}
}
sap 1/1/c2/1:5 {
}
}
vpls "BGP-AD VPLS 6" {
admin-state enable
service-id 6
customer "1"
bgp 1 {
route-distinguisher "64500:6"
route-target {
export "target:64500:6"
import "target:64500:6"
}
pw-template-binding "PW1" {
}
}
bgp-ad {
admin-state enable
vpls-id "64500:6"
vsi-id-prefix 192.0.1.23
}
sap 1/1/c2/1:6 {
}
}
On PE-1, the received L2-VPN BGP routes have next-hop 192.0.1.23:
[/]
A:admin@PE-1# show router bgp routes l2-vpn
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 L2VPN Routes
===============================================================================
Flag RouteType Prefix MED
RD SiteId Label
Nexthop VeId BlockSize LocalPref
As-Path BaseOffset vplsLabelBa
se
-------------------------------------------------------------------------------
u*>i VPLS - - 0
64500:5 - -
192.0.1.23 2 8 100
No As-Path 1 524276
u*>i AutoDiscovery 192.0.1.23 - 0
64500:6 - -
192.0.1.23 - - 100
No As-Path - -
-------------------------------------------------------------------------------
Routes : 2
===============================================================================
On PE-1, the following SDPs with far-end address 192.0.1.23 are auto-created in BGP-VPLS 5 and BGP-AD VPLS 6:
[/]
A:admin@PE-1# show service id 5 sdp
===============================================================================
Services: Service Destination Points
===============================================================================
SdpId Type Far End addr Adm Opr I.Lbl E.Lbl
-------------------------------------------------------------------------------
32766:4294967294 BgpVpls 192.0.1.23 Up Up 524277 524276
-------------------------------------------------------------------------------
Number of SDPs : 1
-------------------------------------------------------------------------------
===============================================================================
[/]
A:admin@PE-1# show service id 6 sdp
===============================================================================
Services: Service Destination Points
===============================================================================
SdpId Type Far End addr Adm Opr I.Lbl E.Lbl
-------------------------------------------------------------------------------
32767:4294967295 BgpAd 192.0.1.23 Up Up 524273 524263
-------------------------------------------------------------------------------
Number of SDPs : 1
-------------------------------------------------------------------------------
===============================================================================
BGP-VPLS 5 and BGP-AD VPLS 6 use a BGP transport tunnel between the "lo3" interfaces, so the corresponding BGP label-IPv4 route is valid, as follows:
[/]
A:admin@PE-1# show router bgp routes label-ipv4
===============================================================================
BGP Router ID:192.0.2.1 AS:64500 Local AS:64500
===============================================================================
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 192.0.1.21/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.22/32 100 None
192.0.2.2 None 10
No As-Path 524286
u*>i 192.0.1.23/32 100 None
192.0.2.2 None 10
No As-Path 524286
i 192.0.1.24/32 100 None
192.0.2.2 None 10
No As-Path 524286
-------------------------------------------------------------------------------
Routes : 4
===============================================================================
Only the BGP tunnel between the "lo4" interfaces is not used by any service, so the last BGP label-IPv4 route is marked invalid in the RIB-IN when selective-label-ipv4-install is configured on PE-1, as follows:
[/]
A:admin@PE-1# show router bgp routes label-ipv4 hunt | match "Invalid" pre-lines 16
Network : 192.0.1.24/32
Nexthop : 192.0.2.2
Path Id : None
From : 192.0.2.2
Res. Nexthop : 192.0.2.2 (ISIS Tunnel)
Local Pref. : 100 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 : 192.0.2.2
Fwd Class : None Priority : None
IPv4 Label : 524286
Flags : Invalid IGP Label-Unicast-No-Svc
Conclusion
The selective-label-ipv4-install command allows BGP-LU IPv4 routes to be marked as invalid in the RIB-IN when these routes are received from a base router BGP peer and not needed by any eligible service. This is a technique to reduce the number of routes in the FIB/LFIB, which is mainly useful for small access routers having small FIB/LFIB sizes.