Case Study—Multi-Homed Inter-AS Provider Network

Figure 7-38 shows an Inter-AS network topology in which Service Provider 1 and Service Provider 2 are providing MPLS VPN services to geographically dispersed Customer A and B sites.

Figure 7-38. Multi-Homed Inter-AS Provider Network

[View full size image]

The provider network uses the RR method to reduce iBGP mesh. P1-AS1-RR and P1-AS2-RR serve as both an ASBR and a RR in the provider network. In this case study, ASBR1-AS1 and ASBR2-AS2 in the provider network use the Inter-AS redistribute connected option to distribute the next hop to devices in Provider Network 1, while P1-AS1-RR and P1-AS2-RR use the Inter-AS next-hop-self method to distribute next-hop information to devices in Provider Network 2. Provider 2, in this case study, also wants to ensure that Customer A traffic uses the Inter-AS Link A and Customer B traffic uses the Inter-AS Link B, and, in case any link goes down, both customers' traffic should be routed across the other operational link. Example 7-31 shows the ASBR and PE router configuration. Refer to Example 7-3 and Example 7-4 for CE configurations.

Example 7-31. Multi-Homed Inter-AS Provider Network Router Configurations

hostname ASBR2-AS1

!

ip cef

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.10.10.102 255.255.255.255

!

interface Ethernet0/0

 ip address 10.10.10.5 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.10.10.10 255.255.255.252

 mpls ip

!

interface Serial2/0

 ip address 10.40.40.1 255.255.255.252

 mpls bgp forwarding

!

router ospf 1

 redistribute connected subnets route-map adv-conn

 network 10.10.10.0 0.0.0.255 area 0

!

router bgp 1

 no bgp default ipv4-unicast

 no bgp default route-target filter

 neighbor 10.10.10.100 remote-as 1

 neighbor 10.10.10.100 update-source Loopback0

 neighbor 10.40.40.2 remote-as 2

 !

 address-family vpnv4

 neighbor 10.10.10.100 activate

 neighbor 10.10.10.100 send-community extended

 neighbor 10.40.40.2 activate

 neighbor 10.40.40.2 send-community extended

 exit-address-family

!

access-list 1 permit 172.16.10.0

access-list 2 permit 192.168.10.0

access-list 10 permit 10.40.40.2

!

route-map adv-conn permit 10

 match ip address 10

__________________________________________________________________________

hostname ASBR2-AS2

!

ip cef

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.20.20.102 255.255.255.255

!

interface Ethernet0/0

 ip address 10.20.20.5 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.20.20.10 255.255.255.252

 mpls ip

!

interface Serial2/0

 ip address 10.40.40.2 255.255.255.252

mpls bgp forwarding

!

router ospf 2

 network 10.20.20.0 0.0.0.255 area 0

!

router bgp 2

 no synchronization

 no bgp default route-target filter

 neighbor 10.20.20.100 remote-as 2

 neighbor 10.20.20.100 update-source Loopback0

 neighbor 10.40.40.1 remote-as 1

 no auto-summary

 !

 address-family vpnv4

 neighbor 10.20.20.100 activate

 neighbor 10.20.20.100 send-community extended

 neighbor 10.20.20.100 next-hop-self

 neighbor 10.40.40.1 activate

 neighbor 10.40.40.1 send-community extended

 neighbor 10.40.40.1 route-map pref_192 in

 neighbor 10.40.40.1 route-map pref_192_local out

 exit-address-family

!

access-list 1 permit 192.168.10.0

access-list 2 permit 172.16.10.0

access-list 3 permit 192.168.20.0

access-list 4 permit 172.16.20.0

!

route-map pref_192_local permit 10

 match ip address 3

!

route-map pref_192_local permit 20

 match ip address 4

 set as-path prepend 65501 65501 65501

!

route-map pref_192 permit 10

 match ip address 1

 set metric 50

!

route-map pref_192 permit 20

 match ip address 2

 set metric 100

__________________________________________________________________________

hostname PE1-AS1

!

ip cef

!

ip vrf Cust_A

 rd 1:100

 route-target export 1:100

 route-target import 2:100

!

ip vrf Cust_B

 rd 1:101

 route-target export 1:101

route-target import 2:101

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.10.10.101 255.255.255.255

!

interface Ethernet0/0

 ip address 10.10.10.1 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.10.10.9 255.255.255.252

 mpls ip

!

interface Serial2/0

 description connected to Cust_A CE1-A

 ip vrf forwarding Cust_A

 ip address 172.16.1.1 255.255.255.252

!

interface Serial3/0

 description connected to Cust_B CE1-B

 ip vrf forwarding Cust_B

 ip address 192.168.1.1 255.255.255.252

!

router ospf 1

 network 10.10.10.0 0.0.0.255 area 0

!

router bgp 1

 no bgp default ipv4-unicast

 neighbor 10.10.10.100 remote-as 1

 neighbor 10.10.10.100 update-source Loopback0

 !

 address-family vpnv4

 neighbor 10.10.10.100 activate

 neighbor 10.10.10.100 send-community extended

 exit-address-family

 !

 address-family ipv4 vrf Cust_B

 neighbor 192.168.1.2 remote-as 65001

 neighbor 192.168.1.2 activate

 neighbor 192.168.1.2 as-override

 no auto-summary

 no synchronization

 exit-address-family

 !

 address-family ipv4 vrf Cust_A

 neighbor 172.16.1.2 remote-as 65001

 neighbor 172.16.1.2 activate

 no auto-summary

 no synchronization

 exit-address-family

__________________________________________________________________________

hostname PE1-AS2

!

ip cef

!

ip vrf Cust_A

 rd 2:100

 route-target export 2:100

 route-target import 1:100

!

ip vrf Cust_B

 rd 2:101

 route-target export 2:101

 route-target import 1:101

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.20.20.101 255.255.255.255

!

interface Ethernet0/0

 ip address 10.20.20.1 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.20.20.9 255.255.255.252

 mpls ip

!

interface Serial2/0

 description coonected to Cust_A CE2-A

 ip vrf forwarding Cust_A

 ip address 172.16.2.1 255.255.255.252

!

interface Serial3/0

 description coonected to Cust_B CE2-B

 ip vrf forwarding Cust_B

 ip address 192.168.2.1 255.255.255.252

!

router ospf 2

 network 10.20.20.0 0.0.0.255 area 0

!

router bgp 2

 no bgp default ipv4-unicast

 neighbor 10.20.20.100 remote-as 2

 neighbor 10.20.20.100 update-source Loopback0

 !

 address-family vpnv4

 neighbor 10.20.20.100 activate

 neighbor 10.20.20.100 send-community extended

 exit-address-family

 !

 address-family ipv4 vrf Cust_B

 neighbor 192.168.2.2 remote-as 65001

 neighbor 192.168.2.2 activate

 neighbor 192.168.2.2 as-override

 no auto-summary

 no synchronization

 exit-address-family

 !

 address-family ipv4 vrf Cust_A

 neighbor 172.16.2.2 remote-as 65002

 neighbor 172.16.2.2 activate

 no auto-summary

 no synchronization

 exit-address-family

__________________________________________________________________________

hostname ASBR1-AS1-RR

!

ip cef

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.10.10.100 255.255.255.255

!

interface Ethernet0/0

 ip address 10.10.10.2 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.10.10.6 255.255.255.252

 mpls ip

!

interface Serial2/0

 ip address 10.30.30.1 255.255.255.252

 mpls bgp forwarding

!

router ospf 1

 redistribute connected subnets route-map adv-conn

 network 10.10.10.0 0.0.0.255 area 0

!

router bgp 1

 no bgp default ipv4-unicast

 no bgp default route-target filter

 neighbor 10.10.10.101 remote-as 1

 neighbor 10.10.10.101 update-source Loopback0

 neighbor 10.10.10.102 remote-as 1

 neighbor 10.30.30.2 remote-as 2

 !

 address-family vpnv4

 neighbor 10.10.10.101 activate

 neighbor 10.10.10.101 send-community extended

 neighbor 10.10.10.101 route-reflector-client

 neighbor 10.10.10.102 activate

 neighbor 10.10.10.102 send-community extended

 neighbor 10.10.10.102 route-reflector-client

 neighbor 10.30.30.2 activate

 neighbor 10.30.30.2 send-community extended

 exit-address-family

!

access-list 10 permit 10.30.30.2

!

route-map adv-conn permit 10

 match ip address 10

__________________________________________________________________________

hostname ASBR1-AS2-RR

!

ip cef

!

mpls ldp router-id Loopback0

!

interface Loopback0

 ip address 10.20.20.100 255.255.255.255

!

interface Ethernet0/0

 ip address 10.20.20.2 255.255.255.252

 mpls ip

!

interface Ethernet1/0

 ip address 10.20.20.6 255.255.255.252

 mpls ip

!

interface Serial2/0

 ip address 10.30.30.2 255.255.255.252

 mpls bgp forwarding

!

router ospf 2

 network 10.20.20.0 0.0.0.255 area 0

!

router bgp 2

 no synchronization

 no bgp default route-target filter

 neighbor 10.20.20.101 remote-as 2

 neighbor 10.20.20.101 update-source Loopback0

 neighbor 10.20.20.102 remote-as 2

 neighbor 10.20.20.102 update-source Loopback0

 neighbor 10.30.30.1 remote-as 1

 no auto-summary

 !

 address-family vpnv4

 neighbor 10.20.20.101 activate

 neighbor 10.20.20.101 send-community extended

 neighbor 10.20.20.101 route-reflector-client

 neighbor 10.20.20.101 next-hop-self

 neighbor 10.20.20.102 activate

 neighbor 10.20.20.102 send-community extended

 neighbor 10.20.20.102 route-reflector-client

 neighbor 10.20.20.102 next-hop-self

 neighbor 10.30.30.1 activate

 neighbor 10.30.30.1 send-community extended

 neighbor 10.30.30.1 route-map pref_172 in

 neighbor 10.30.30.1 route-map pref_172_local out

 exit-address-family

!

access-list 1 permit 172.16.10.0

access-list 2 permit 192.168.10.0

access-list 3 permit 172.16.20.0

access-list 4 permit 192.168.20.0

!

route-map pref_172_local permit 10

 match ip address 3

!

route-map pref_172_local permit 20

 match ip address 4

 set as-path prepend 65501 65501 65501

!

route-map pref_172 permit 10

 match ip address 1

 set metric 50

!

route-map pref_172 permit 20

 match ip address 2

 set metric 100

Example 7-32 shows that, on PE1-AS1, 172.16.20.0/24 is reachable via Inter-AS Link A, and 192.168.20.0/24 is reachable via Inter-AS Link B. Based on the output shown in Example 7-32, traffic between Customer A sites take Inter-AS Link A and traffic between Customer B sites take Inter-AS Link B.

Example 7-32. Verifying End-to-End Connectivity

PE1-AS1#show ip bgp vpnv4 all

<truncated>

*>i172.16.20.0/24  10.30.30.2          0   100      0 2 65002 i

*>i192.168.20.0    10.40.40.2          0   100      0 2 65001 i

__________________________________________________________________________

PE1-AS2#show ip bgp vpnv4 all

<truncated>

*>i172.16.10.0/24  10.20.20.100       50   100      0 1 65001 i

*>i192.168.10.0    10.20.20.102       50   100      0 1 65001 i

Example 7-33 shows the result of the ping operation.

Example 7-33. Verify End-to-End Connectivity

CE1-A#ping 172.16.20.1 source 172.16.10.1



Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 172.16.20.1, timeout is 2 seconds:

Packet sent with a source address of 172.16.10.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/60 ms

__________________________________________________________________________

CE1-B#ping 192.168.20.1 source 192.168.10.1



Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 192.168.20.1, timeout is 2 seconds:

Packet sent with a source address of 192.168.10.1

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 60/60/60 ms