1. Customer A.
         1.1 Remove static routing configuration from the previous task.
         1.2 Use ISIS as routing protocol on routers R6 & R7, and between Customer A and SP routers.
         1.3 Configure ISIS protocol to only create Level-2 databases.

2. Customer B.
         2.1 Remove OSPF routing configuration from the previous task.
         2.2 Use BGP as routing protocol between Customer B and SP routers. Both customer routers                    should use AS #48. Each router should advertise it's /24 range into eBGP.
         2.3 Customer routers should see the BGP route towards the other site with "correct" AS-PATH                  of "17 48 i".
         

Highlight the text below to reveal the solution.

This task requires understanding of using ISIS and eBGP for CE-PE routing. 

Requirement #1 - configure "is-type" of level-2 on routers R6, R7, R5 and R2 to only create Level-2                                databases. Redistribute between ISIS and BGP on PE routers, note to redistribute                                  the correct ISIS level routes. 

Requirement #2 - The challenge in this task is that routers R4 and R8 are useing the same AS                                           number. In order to keep the AS-PATH as required, configure "allowas-in" on                                     eBGP session towards the PE router. 
                              Note that IOS-XR has an additional loop prevention feature, which does not exist                                 in IOS. Router R3 will not advertise the prefix 10.10.4.0/24 to R8, unless                                               "as-path-loopcheck" is disable in the vrf configuration. 
                              Also note that IOS-XR requires explicit configuration of inbound and outbound                                   route-policy for eBGP peers, otherwise no prefixes will be advertised or accepted                                 from neighbor. 

R2:

!
interface Ethernet1/1
 vrf forwarding CUST_A
 ip address 17.0.27.2 255.255.255.0
 ip router isis CUST_A
router isis CUST_A
 vrf CUST_A
 net 49.0007.0000.0000.0002.00
 is-type level-2-only
 redistribute bgp 17
!
router bgp 17
 bgp log-neighbor-changes
 no bgp default ipv4-unicast
 neighbor 17.0.1.1 remote-as 17
 neighbor 17.0.1.1 update-source Loopback0
 !
 address-family ipv4
 exit-address-family
 !
 address-family vpnv4
  neighbor 17.0.1.1 activate
  neighbor 17.0.1.1 send-community both
 exit-address-family
 !
 address-family ipv4 vrf CUST_A
  redistribute connected
  redistribute isis CUST_A level-1-2
 exit-address-family
 !
 address-family ipv4 vrf CUST_B
  redistribute connected
  neighbor 17.0.24.4 remote-as 48
  neighbor 17.0.24.4 activate
 exit-address-family
!

R3:

R4:

R5:

R6:

R7:

R8:

Verification: