Carrier Supporting Carrier

This lab showcases a Carrier Supporting Carrier setup. It shows a Customer with two sites connected to ISP1 who in turn, has two disparate areas connected via a Backbone Provider implementing CsC. Customer A has two sites connected to ISP1 in a VRF called CUST_1.

The following are the primary features of this CsC design:

IS-IS and LDP is used throughout ISP1.
ISP1 has one route reflector in each area running VPNv4 to the PE routers, and between each other.
The connection between ASBR1 and BB-PE1 is running OSPF and LDP.
The loopbacks of RR1 and PE1 are redistributed from IS-IS into OSPF and sent to BB-PE1.
ASBR1 also redistributes from OSPF into IS-IS (this is expected to be loopbacks for RR2 and PE2).
The connection between ASBR2 and BB-PE2 is running BGP-LU.
The loopbacks for RR2 and PE2 are advertised to BB-PE2.
Instead of redistributing into the local IGP, ASRB1 runs BGP-LU to RR2 who in turn runs BGP-LU to PE2 into order to communicate the label for PE1.
The customer subnets are represented by loopbacks on the CE routers.

For full details on how CsC works check out this document.