Scenario
This comparison shows how Carrier Supporting Carrier is configured from the point of view of BB-PE2, an edge router for the backbone provider. OSPF + LDP is the internal configuration for the Backbone Provider. BGP-LU is configured between BB-PE2 and ASBR2.
This is best viewed alongside this CsC cheatsheet or this GNS3 lab.
There is an alternate approach to CsC, using IGP+LDP between the Backbone Provider and the Customer Provider Edge Routers, but IOS-XR does not support VRF aware LDP. This means that in such as setup, an IOS-XR cannot play the role of the Backbone Edge Router.
IOS Config
hostname BB-PE2 ! ip cef ! ip vrf CSC_CUST_ISP1 rd 100:500 route-target export 100:500 route-target import 100:500 ! ! ! interface Loopback0 ip address 100.2.2.2 255.255.255.255 ip ospf 1 area 0 ! interface GigabitEthernet0/1 description link to ASBR2 ip vrf forwarding CSC_CUST_ISP1 ip address 192.168.117.6 255.255.255.252 ! interface GigabitEthernet0/0 description link to BB-Core ip address 10.30.23.2 255.255.255.0 ip ospf 1 area 0 ! router ospf 1 mpls ldp autoconfig router-id 100.2.2.2 log-adjacency-changes passive-interface Loopback0 ! router bgp 100 bgp router-id 100.2.2.2 no bgp default ipv4-unicast bgp log-neighbor-changes neighbor 100.1.1.1 remote-as 100 neighbor 100.1.1.1 update-source Loopback0 ! address-family vpnv4 neighbor 100.1.1.1 activate neighbor 100.1.1.1 send-community extended neighbor 100.1.1.1 next-hop-self exit-address-family ! address-family ipv4 vrf CSC_CUST_ISP1 neighbor 192.168.117.5 remote-as 500 neighbor 192.168.117.5 activate neighbor 192.168.117.5 send-label no synchronization exit-address-family ! |
XR Config
hostname BB-PE2 ! vrf CSC_CUST_ISP1 address-family ipv4 unicast import route-target 100:500 ! export route-target 100:500 ! ! ! interface Loopback0 ipv4 address 100.2.2.2 255.255.255.255 ! interface GigabitEthernet0/0/0/1 description link to ASBR2 vrf CSC_CUST_ISP1 ipv4 address 192.168.117.6 255.255.255.252 ! interface GigabitEthernet0/0/0/0 description link to BB-Core ipv4 address 10.30.23.2 255.255.255.0 ! route-policy PASS pass end-policy ! ! XR devices cannot label switch to a next-hop ! that is not learned via a /32 host. Hence the ! need for a static route here. router static vrf CSC_CUST_ISP1 address-family ipv4 unicast 192.168.117.5/32 GigabitEthernet0/0/0/1 ! ! ! router ospf 1 log adjacency changes address-family ipv4 unicast area 0 mpls ldp auto-config interface Loopback0 passive enable ! interface GigabitEthernet0/0/0/0 ! ! ! router bgp 100 bgp router-id 100.2.2.2 bgp log neighbor changes detail address-family vpnv4 unicast ! neighbor 100.1.1.1 remote-as 100 update-source Loopback0 address-family vpnv4 unicast next-hop-self ! ! vrf CSC_CUST_ISP1 rd 100:500 ! Note the need to specify allocate-label all on XR under ! the bgp vrf config address-family ipv4 unicast allocate-label all ! neighbor 192.168.117.5 remote-as 500 address-family ipv4 labeled-unicast route-policy PASS in route-policy PASS out ! ! ! ! ! Remember to enable LDP globally mpls ldp address-family ipv4 ! ! |
