Option 4: Non-VPN Transit Provider

In this approach, multiple VPN providers use another MPLS-enabled service provider as a transit backbone to exchange MPLS VPN routes. Figure 7-31 shows a multiprovider MPLS VPN network using AS100 as a transit provider to transport VPN routes.

Figure 7-31. Inter-AS Using a Non-VPN Transit Provider

[View full size image]

In this option, a multi-hop MP-eBGP session is formed between the two RRs belonging to the two different providers. To implement this option, BGP next hops need to be propagated and an end-to-end LSP path needs to be maintained.

P1-AS1-RR and P1-AS2-RR are RRs that are local in each of the provider’s network. An MP-eBGP session is formed between the RRs to transport VPNv4 information across the multiprovider network. An eBGP session is formed between the ASBR1-AS1 and ASBR1-AS100. Another eBGP session is formed between ASBRs in AS2 and AS100.

Control Plane Forwarding in Option 4

Figure 7-32 shows the control plane forwarding action that takes place for prefix 172.16.10.0/24 advertised by CE1-A to CE2-A that belongs to the same VPN, CUST_A.

Figure 7-32. Control Plane Operation in a Non-VPN Transit Provider Network

[View full size image]

Data Forwarding in Option 4

The source and destination networks are located on two different MPLS VPN provider networks. The data forwarding path originates from the source address of the flow, which is 172.16.20.1 destined to 172.16.10.1. Figure 7-33 traces the path of the data packet from the source to the destination.

Figure 7-33. Data Forwarding in Option 4

[View full size image]

Configuration Flowchart in Option 4

Figure 7-34 shows the configuration steps that are involved in accomplishing a functional Inter-AS network using option 4.

Figure 7-34. MPLS VPN Network Using Option 4

[View full size image]

Configuration and Verification of Option 4

Figure 7-31 illustrated a multiprovider MPLS VPN network in which sites in VPN-A are geographically dispersed. Site 1 in VPN-A is connected to PE1-AS1 in AS1, and Site 2 in VPN-A is connected to PE1-AS2 in AS2. EBGP peering is configured between ASBRs:

  • ASBR1-AS1 and ASBR1-AS100

  • ASBR1-AS2 and ASBR2-AS100

The steps to configure are

Step 1.
Configure transit VPN network, AS100—Configure the ASBR Routers ASBR1-AS100 and ASBR2-AS100 for IGP, as shown in Example 7-23. In this case, OSPF is used. Configure iBGP peering between the two ASBRs for eBGP. Use neighbor send-label to enable exchange of IPv4 label exchange between the two peers.

Example 7-23. Configure Transit VPN Network, AS100
ASBR1-AS100(config)#interface Loopback0
ASBR1-AS100(config-if)# ip address 172.16.100.101 255.255.255.255
ASBR1-AS100(config-if)#interface Serial0/0
ASBR1-AS100(config-if)# ip address 172.16.100.1 255.255.255.252
ASBR1-AS100(config-if)# mpls ip
ASBR1-AS100(config-if)#interface Serial1/0
ASBR1-AS100(config-if)# ip address 172.16.3.2 255.255.255.252
ASBR1-AS100(config-if)#router ospf 100
ASBR1-AS100(config-router)# network 172.16.100.0 0.0.0.255 area 0
ASBR1-AS100(config-router)#router bgp 100
ASBR1-AS100(config-router)# network 172.16.100.101 mask 255.255.255.255
ASBR1-AS100(config-router)# neighbor 172.16.3.1 remote-as 1
ASBR1-AS100(config-router)# neighbor 172.16.3.1 send-label
ASBR1-AS100(config-router)# neighbor 172.16.100.102 remote-as 100
ASBR1-AS100(config-router)# neighbor 172.16.100.102 update-source Loopback0
ASBR1-AS100(config-router)# neighbor 172.16.100.102 next-hop-self
ASBR1-AS100(config-router)# neighbor 172.16.100.102 send-label
___________________________________________________________________________
ASBR2-AS100(config)#interface Loopback0
ASBR2-AS100(config-if)# ip address 172.16.100.102 255.255.255.255
ASBR2-AS100(config-if)#interface Serial0/0
ASBR2-AS100(config-if)# ip address 172.16.100.2 255.255.255.252
ASBR2-AS100(config-if)# mpls ip
ASBR2-AS100(config-if)#interface Serial1/0
ASBR2-AS100(config-if)# ip address 172.16.4.2 255.255.255.252
ASBR2-AS100(config-if)#router ospf 100
ASBR2-AS100(config-router)# network 172.16.100.0 0.0.0.255 area 0
ASBR2-AS100(config-router)#router bgp 100
ASBR2-AS100(config-router)# network 172.16.100.102 mask 255.255.255.255
ASBR2-AS100(config-router)# neighbor 172.16.4.1 remote-as 2
ASBR2-AS100(config-router)# neighbor 172.16.4.1 send-label
ASBR2-AS100(config-router)# neighbor 172.16.100.101 remote-as 100
ASBR2-AS100(config-router)# neighbor 172.16.100.101 update-source Loopback0
ASBR2-AS100(config-router)# neighbor 172.16.100.101 next-hop-self
ASBR2-AS100(config-router)# neighbor 172.16.100.101 send-label

Step 2.
Configure ASBR routers in AS1 and AS2—In this step, the ASBR routers are configured to perform eBGP peering with transit VPN providers ASBR routers, ASBR1-AS100 and ASBR2-AS100. The loopbacks on PE and RR routers are advertised in BGP on the ASBR routers, and the BGP routes are redistributed in OSPF to ensure reachability. Example 7-24 demonstrates the step. Note that mpls bgp forwarding is added by default when MP-eBGP is established between ASBR1-AS1 and ASBR1-AS100. You will see this command under the serial interface in the final configurations.

Example 7-24. Configure ASBR Routers in AS1 and AS2
ASBR1-AS1(config)#interface Loopback0
ASBR1-AS1(config-if)# ip address 10.10.10.102 255.255.255.255
ASBR1-AS1(config-if)# exit
ASBR1-AS1(config)#mpls ldp router-id Loopback0
ASBR1-AS1(config)#interface Serial0/0
ASBR1-AS1(config-if)# ip address 10.10.10.5 255.255.255.252
ASBR1-AS1(config-if)# mpls ip
ASBR1-AS1(config-if)#interface Serial1/0
ASBR1-AS1(config-if)# ip address 172.16.3.1 255.255.255.252
ASBR1-AS1(config-if)# mpls bgp forwarding
ASBR1-AS1(config-if)#router ospf 1
ASBR1-AS1(config-router)# router-id 10.10.10.102
ASBR1-AS1(config-router)# network 10.0.0.0 0.255.255.255 area 0
ASBR1-AS1(config-router)#router bgp 1
ASBR1-AS1(config-router)# network 10.10.10.101 mask 255.255.255.255
ASBR1-AS1(config-router)# network 10.10.10.200 mask 255.255.255.255
ASBR1-AS1(config-router)# neighbor 10.10.10.200 remote-as 1
ASBR1-AS1(config-router)# neighbor 10.10.10.200 update-source Loopback0
ASBR1-AS1(config-router)# neighbor 10.10.10.200 next-hop-self
ASBR1-AS1(config-router)# neighbor 10.10.10.200 send-label
ASBR1-AS1(config-router)# neighbor 172.16.3.2 remote-as 100
ASBR1-AS1(config-router)# neighbor 172.16.3.2 send-label
________________________________________________________________________
ASBR2-AS2(config)#interface Loopback0
ASBR2-AS2(config-if)# ip address 10.20.20.102 255.255.255.255
ASBR2-AS2(config-if)#exit
ASBR2-AS2(config)#mpls ldp router-id Loopback0
ASBR2-AS2(config-if)#interface Serial0/0
ASBR2-AS2(config-if)# ip address 10.20.20.5 255.255.255.252
ASBR2-AS2(config-if)# mpls ip
ASBR2-AS2(config-if)#interface Serial1/0
ASBR2-AS2(config-if)# ip address 172.16.4.1 255.255.255.252
ASBR2-AS2(config-if)#router ospf 2
ASBR2-AS2(config-router)# router-id 10.20.20.102
ASBR2-AS2(config-router)# network 10.0.0.0 0.255.255.255 area 0
ASBR2-AS2(config-router)#router bgp 2
ASBR2-AS2(config-router)# network 10.20.20.101 mask 255.255.255.255
ASBR2-AS2(config-router)# network 10.20.20.200 mask 255.255.255.255
ASBR2-AS2(config-router)# neighbor 10.20.20.200 remote-as 2
ASBR2-AS2(config-router)# neighbor 10.20.20.200 update-source Loopback0
ASBR2-AS2(config-router)# neighbor 10.20.20.200 next-hop-self
ASBR2-AS2(config-router)# neighbor 10.20.20.200 send-label
ASBR2-AS2(config-router)# neighbor 172.16.4.2 remote-as 100
ASBR2-AS2(config-router)# neighbor 172.16.4.2 send-label

Step 3.
Configure MP-eBGP session between the RRs—In this step, you configure an MP-eBGP session between the RR as shown in Example 7-25. Before performing this step, ensure that the loopback addresses on the RRs are reachable. Ensure that P1-AS1-RR and P1-AS2-RR serve both as an IPv4 and VPNv4 RR.

Example 7-25. Configure MP-eBGP Session Between the RRs
P1-AS1-RR(config)#router bgp 1
P1-AS1-RR(config-router)# no bgp default ipv4-unicast
P1-AS1-RR(config-router)# neighbor 10.10.10.101 remote-as 1
P1-AS1-RR(config-router)# neighbor 10.10.10.101 update-source Loopback0
P1-AS1-RR(config-router)# neighbor 10.10.10.102 remote-as 1
P1-AS1-RR(config-router)# neighbor 10.10.10.102 update-source Loopback0
P1-AS1-RR(config-router)# neighbor 10.20.20.200 remote-as 2
P1-AS1-RR(config-router)# neighbor 10.20.20.200 ebgp-multihop 10
P1-AS1-RR(config-router)# neighbor 10.20.20.200 update-source Loopback0
P1-AS1-RR(config-router)# address-family ipv4
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 activate
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 route-reflector-client
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 next-hop-self
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 send-label
P1-AS1-RR(config-router-af)# neighbor 10.10.10.102 activate
P1-AS1-RR(config-router-af)# neighbor 10.10.10.102 route-reflector-client
P1-AS1-RR(config-router-af)# neighbor 10.10.10.102 next-hop-self
P1-AS1-RR(config-router-af)# neighbor 10.10.10.102 send-label
P1-AS1-RR(config-router-af)# exit-address-family
P1-AS1-RR(config-router)# address-family vpnv4
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 activate
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 send-community extended
P1-AS1-RR(config-router-af)# neighbor 10.10.10.101 route-reflector-client
P1-AS1-RR(config-router-af)# neighbor 10.20.20.200 activate
P1-AS1-RR(config-router-af)# neighbor 10.20.20.200 send-community extended
P1-AS1-RR(config-router-af)# neighbor 10.20.20.200 next-hop-unchanged
___________________________________________________________________________
P1-AS2-RR(config)#router bgp 2
P1-AS2-RR(config-router)# no bgp default ipv4-unicast
P1-AS2-RR(config-router)# neighbor 10.10.10.200 remote-as 1
P1-AS2-RR(config-router)# neighbor 10.10.10.200 ebgp-multihop 10
P1-AS2-RR(config-router)# neighbor 10.10.10.200 update-source Loopback0
P1-AS2-RR(config-router)# neighbor 10.20.20.101 remote-as 2
P1-AS2-RR(config-router)# neighbor 10.20.20.101 update-source Loopback0
P1-AS2-RR(config-router)# neighbor 10.20.20.102 remote-as 2
P1-AS2-RR(config-router)# neighbor 10.20.20.102 update-source Loopback0
P1-AS2-RR(config-router)# address-family ipv4
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 activate
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 route-reflector-client
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 next-hop-self
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 send-label
P1-AS2-RR(config-router-af)# neighbor 10.20.20.102 activate
P1-AS2-RR(config-router-af)# neighbor 10.20.20.102 route-reflector-client
P1-AS2-RR(config-router-af)# neighbor 10.20.20.102 next-hop-self
P1-AS2-RR(config-router-af)# neighbor 10.20.20.102 send-label
P1-AS2-RR(config-router-af)# exit-address-family
P1-AS2-RR(config-router)# address-family vpnv4
P1-AS2-RR(config-router-af)# neighbor 10.10.10.200 activate
P1-AS2-RR(config-router-af)# neighbor 10.10.10.200 send-community extended
P1-AS2-RR(config-router-af)# neighbor 10.10.10.200 next-hop-unchanged
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 activate
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 send-community extended
P1-AS2-RR(config-router-af)# neighbor 10.20.20.101 route-reflector-client

ASBR and RR Configurations in Option 4

Example 7-26 shows the ASBR1, ASBR2, and RR configurations when using option 4.

Example 7-26. ASBR and RR Configurations
hostname ASBR1-AS1
							!
							ip cef
							!
							mpls ldp router-id Loopback0
							!
							interface Loopback0
							ip address 10.10.10.102 255.255.255.255
							!
							interface Serial0/0
							ip address 10.10.10.5 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 172.16.3.1 255.255.255.252
							mpls bgp forwarding
							!
							router ospf 1
							router-id 10.10.10.102
							redistribute bgp 1 metric 1 subnets route-map from_AS100
							network 10.0.0.0 0.255.255.255 area 0
							!
							router bgp 1
							no synchronization
							network 10.10.10.101 mask 255.255.255.255
							network 10.10.10.102 mask 255.255.255.255
							network 10.10.10.200 mask 255.255.255.255
							network 100.100.100.100 mask 255.255.255.255
							neighbor 172.16.3.2 remote-as 100
							neighbor 172.16.3.2 send-label
							no auto-summary
							!
							ip access-list standard from_AS100
							permit 10.20.20.102
							permit 10.20.20.101
							permit 172.16.100.101
							permit 172.16.100.102
							permit 10.20.20.200
							!
							route-map from_AS100 permit 10
							match ip address from_AS100
_________________________________________________________________________
hostname ASBR2-AS2
							!
							ip cef
							!
							mpls ldp router-id Loopback0
							!
							interface Loopback0
							ip address 10.20.20.102 255.255.255.255
							!
							interface Serial0/0
							ip address 10.20.20.5 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 172.16.4.1 255.255.255.252
							mpls bgp forwarding
							!
							router ospf 2
							router-id 10.20.20.102
							redistribute bgp 2 metric 1 subnets route-map from_AS100
							network 10.0.0.0 0.255.255.255 area 0
							!
							router bgp 2
							no synchronization
							network 10.20.20.101 mask 255.255.255.255
							network 10.20.20.102 mask 255.255.255.255
							network 10.20.20.200 mask 255.255.255.255
							network 100.100.100.101 mask 255.255.255.255
							neighbor 172.16.4.2 remote-as 100
							neighbor 172.16.4.2 send-label
							no auto-summary
							!
							ip access-list standard from_AS100
							permit 10.10.10.102
							permit 10.10.10.101
							permit 172.16.100.101
							permit 172.16.100.102
							permit 10.10.10.200
							!
							route-map from_AS100 permit 10
							match ip address from_AS100
_________________________________________________________________________
hostname ASBR1-AS100
							!
							ip cef
							!
							interface Loopback0
							ip address 172.16.100.101 255.255.255.255
							!
							interface Serial0/0
							ip address 172.16.100.1 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 172.16.3.2 255.255.255.252
							mpls bgp forwarding
							!
							router ospf 100
							network 172.16.100.0 0.0.0.255 area 0
							!
							router bgp 100
							no synchronization
							network 172.16.100.101 mask 255.255.255.255
							neighbor 172.16.3.1 remote-as 1
							neighbor 172.16.3.1 send-label
							neighbor 172.16.100.102 remote-as 100
							neighbor 172.16.100.102 next-hop-self
							neighbor 172.16.100.102 update-source Loopback0
							neighbor 172.16.100.102 send-label
							no auto-summary
_________________________________________________________________________
hostname ASBR2-AS100
							!
							ip cef
							!
							interface Loopback0
							ip address 172.16.100.102 255.255.255.255
							!
							interface Serial0/0
							ip address 172.16.100.2 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 172.16.4.2 255.255.255.252
							mpls bgp forwarding
							!
							router ospf 100
							network 172.16.100.0 0.0.0.255 area 0
							!
							router bgp 100
							no synchronization
							network 172.16.100.102 mask 255.255.255.255
							neighbor 172.16.4.1 remote-as 2
							neighbor 172.16.4.1 send-label
							neighbor 172.16.100.101 remote-as 100
							neighbor 172.16.100.101 update-source Loopback0
							neighbor 172.16.100.101 next-hop-self
							neighbor 172.16.100.101 send-label
							no auto-summary
_________________________________________________________________________
hostname P1-AS1-RR
							!
							ip cef
							!
							mpls ldp router-id Loopback0
							!
							interface Loopback0
							ip address 10.10.10.200 255.255.255.255
							!
							interface Serial0/0
							ip address 10.10.10.2 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 10.10.10.6 255.255.255.252
							mpls ip
							!
							router ospf 1
							router-id 10.10.10.200
							network 10.0.0.0 0.255.255.255 area 0
							!
							router bgp 1
							no bgp default ipv4-unicast
							neighbor 10.10.10.101 remote-as 1
							neighbor 10.10.10.101 update-source Loopback0
							neighbor 10.20.20.200 remote-as 2
							neighbor 10.20.20.200 ebgp-multihop 255
							neighbor 10.20.20.200 update-source Loopback0
							!
							address-family vpnv4
							neighbor 10.10.10.101 activate
							neighbor 10.10.10.101 route-reflector-client
							neighbor 10.10.10.101 send-community extended
							neighbor 10.20.20.200 activate
							neighbor 10.20.20.200 next-hop-unchanged
							neighbor 10.20.20.200 send-community extended
							exit-address-family
							hostname P1-AS2-RR
							!
							ip cef
							!
							mpls ldp router-id Loopback0
							!
							interface Loopback0
							ip address 10.20.20.200 255.255.255.255
							!
							interface Serial0/0
							ip address 10.20.20.6 255.255.255.252
							mpls ip
							!
							interface Serial1/0
							ip address 10.20.20.2 255.255.255.252
							mpls ip
							!
							router ospf 2
							router-id 10.20.20.200
							network 10.0.0.0 0.255.255.255 area 0
							!
							router bgp 2
							no bgp default ipv4-unicast
							neighbor 10.10.10.200 remote-as 1
							neighbor 10.10.10.200 ebgp-multihop 255
							neighbor 10.10.10.200 update-source Loopback0
							neighbor 10.20.20.101 remote-as 2
							neighbor 10.20.20.101 update-source Loopback0
							!
							address-family vpnv4
							neighbor 10.10.10.200 activate
							neighbor 10.10.10.200 next-hop-unchanged
							neighbor 10.10.10.200 send-community extended
							neighbor 10.20.20.101 activate
							neighbor 10.20.20.101 route-reflector-client
							neighbor 10.20.20.101 send-community extended
							exit-address-family

Verifying Inter-Provider VPN Operation Using Option 4

The steps to verify inter-provider VPN operation using option 4 are

Step 1.
Verify control plane forwarding with option 4—Figure 7-35 shows the control plane forwarding operation when the 172.16.10.0/24 prefix is propagated across the multiprovider networks AS1 and AS2 to CE2-A.

Figure 7-35. Control Plane Forwarding in Option 4

[View full size image]

Step 2.
Verify data forwarding in option 4—Figure 7-36 shows the data plane forwarding operation when a packet is sent from 172.16.20.1 to 172.16.10.1.

Figure 7-36. Data Forwarding in Option 4

[View full size image]

Step 3.
Verify end-to-end connectivity via ping—Verify end-to-end connectivity between Customer A networks (172.16.10.0/24 and 172.16.20.0/24) and Customer B networks (192.168.10.0/24 and 192.168.20.0/24). Example 7-27 shows the result of the ping operation.

Example 7-27. 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 = 140/140/140 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 = 132/138/140 ms

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