Exploring the quirks of Network Engineering
Scenario
R1 and R3 are PE routers. R2 is a P router. A pseudowire (aka xconnect) is configured between R1 and R3 with VCID 100. The R1 interface assigned to the pseudowire is Gi0/0/0/0.10. IS-IS is configured to advertise the loopbacks used for the xconnects (connected subnets are advertised too but not needed). The relevant config for R1 is shown.
IOS Config
hostname R1
!
pseudowire-class CLASS_ONE
encapsulation mpls
!
interface Loopback0
ip address 1.1.1.1 255.255.255.255
!
interface GigabitEthernet0/0/0/0.10
description Pseudowire Subinterface
encapsulation dot1Q 10
xconnect 3.3.3.3 100 pw-class CLASS_ONE
!
interface GigabitEthernet0/0/0/1
description link to R2
ip address 10.1.2.1 255.255.255.252
ip router isis LAB
mpls ip
isis circuit-type level-2-only
isis network point-to-point
isis csnp-interval 10
!
router isis LAB
net 49.0500.0000.0000.0002.00
is-type level-2-only
passive-interface Loopback0
!
XR Config
hostname R1
!
interface Loopback0
ipv4 address 1.1.1.1 255.255.255.255
!
interface GigabitEthernet0/0/0/0.10 l2transport
encapsulation dot1q 10
!
interface GigabitEthernet0/0/0/1
description link to R2
ipv4 address 10.1.2.1 255.255.255.252
!
router isis LAB
is-type level-2-only
net 49.0500.0000.0000.0002.00
address-family ipv4 unicast
!
interface Loopback0
passive
address-family ipv4 unicast
!
!
interface GigabitEthernet0/0/0/1
circuit-type level-2-only
point-to-point
address-family ipv4 unicast
!
!
!
l2vpn
xconnect group XCONNECT-GROUP-ONE
p2p XCONNECT
interface GigabitEthernet0/0/0/0.10
neighbor ipv4 3.3.3.3 pw-id 100
!
!
!
!
mpls ldp
router-id 1.1.1.1
interface GigabitEthernet0/0/0/1
!
!
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