Example for Configuring Inter-AS VPN Option C (Solution 1)

After establishing a multi-hop MP-EBGP peer relationship between PEs of different ASs, you can implement the inter-AS VPN OptionC solution.

Networking Requirements

On the network shown in Figure 1, CE1 and CE2 belong to the same VPN; CE1 accesses the network through PE1 in AS100; CE2 accesses the network through PE2 in AS200.

It is required that inter-AS BGP/MPLS IP VPN be implemented in Option C mode.

Figure 1 Inter-AS VPN Option C (solution 1)

Interfaces 1 and 2 in this example represent GE 0/1/0 and GE 0/1/8, respectively.

Configuration Roadmap

The configuration roadmap is as follows:

Set up an MP-EBGP peer relationship between PEs in different ASs and configure the maximum number of hops between PEs.
Configure a routing policy on ASBRs, so that each ASBR assigns MPLS labels to the loopback routes received from the PE in the local AS before advertising the routes to the remote ASBR and assigns new MPLS labels to the routes advertised to the PE in the local AS if they are labeled IPv4 routes.
Configure the PE and ASBR in the same AS to exchange labeled IPv4 routes.
Configure the ASBRs to exchange labeled IPv4 routes.

Data Preparation

To complete the configuration, you need the following data:

MPLS LSR IDs of PE1 (1.1.1.9), ASBR1 (2.2.2.9), ASBR2 (3.3.3.9), and PE2 (4.4.4.9)
Name (vpn1), RD (100:1), and export and import VPN targets (1:1) of the VPN instance on each PE
Routing policies configured on the ASBR

Procedure

Configure an IGP on the MPLS backbone network in AS100 and AS200, so that the PE and ASBR in the same AS can communicate.
This example uses OSPF as the IGP.

The 32-bit loopback interface address used as the LSR ID should be advertised by OSPF.

After the configurations are complete, the OSPF neighbor relationship can be established between the ASBR and PE in the same AS. Run the display ospf peer command. The command output shows that the status of the OSPF neighbor relationship is Full.

The following example uses the command output on PE1.
```
<PE1> display ospf peer
          OSPF Process 1 with Router ID 1.1.1.9
                  Neighbors
 Area 0.0.0.0 interface 10.10.1.2(GigabitEthernet0/1/0)'s neighbors
 Router ID: 2.2.2.9          Address: 10.10.1.1
   State: Full  Mode:Nbr is  Master  Priority: 1
   DR: 10.10.1.1   BDR: 10.10.1.2   MTU: 0
   Dead timer due in 31  sec
   Retrans timer interval: 5
   Neighbor is up for 00:28:11
   Authentication Sequence: [ 0 ]
```
The ASBR and PE in the same AS can learn the routes to each other's loopback interface and ping each other.
Configure MPLS and MPLS LDP both globally and per interface on each node of the MPLS backbone networks in AS100 and AS200 and set up LDP LSPs.
For configuration details, see Configuration Files in this section.
Set up IBGP peer relationships between the PEs and ASBRs in the same AS.
For configuration details, see Configuration Files in this section.
Configure the VPN instance on the PE and configure the CE to access the PE.
For configuration details, see Configuration Files in this section.

The import VPN target configured on PE1 must be the same as the export VPN target configured on PE2; the export VPN target configured on PE1 must be the same as the import VPN target configured on PE2.

Configure the function to exchange labeled IPv4 routes.

# Configure PE1 to exchange labeled IPv4 routes with ASBR1.

[~PE1] bgp 100
[*PE1-bgp] peer 2.2.2.9 label-route-capability
[*PE1-bgp] quit
[*PE1] commit

# Enable MPLS on GE 0/1/8 that connects ASBR1 to ASBR2.

[~ASBR1] interface gigabitethernet 0/1/8
[~ASBR1-GigabitEthernet0/1/8] ip address 10.21.1.1 24
[*ASBR1-GigabitEthernet0/1/8] mpls
[*ASBR1-GigabitEthernet0/1/8] quit
[*ASBR1] commit

# Configure routing policies on ASBR1.

[~ASBR1] route-policy policy1 permit node 1
[*ASBR1-route-policy] apply mpls-label
[*ASBR1-route-policy] quit
[*ASBR1] route-policy policy2 permit node 1
[*ASBR1-route-policy] if-match mpls-label
[*ASBR1-route-policy] apply mpls-label
[*ASBR1-route-policy] quit
[*ASBR1] commit

# Apply the routing policies to the routes advertised to PE1 and enable ASBR1 to exchange label IPv4 routes with PE1.

[~ASBR1] bgp 100
[*ASBR1-bgp] peer 1.1.1.9 route-policy policy2 export
[*ASBR1-bgp] peer 1.1.1.9 label-route-capability

# Apply the routing policies to the routes advertised to ASBR2 and enable ASBR1 to exchange label IPv4 routes with ASBR2.

[*ASBR1-bgp] peer 10.21.1.2 as-number 200
[*ASBR1-bgp] peer 10.21.1.2 route-policy policy1 export
[*ASBR1-bgp] peer 10.21.1.2 label-route-capability
[*ASBR1-bgp] quit

# Configure ASBR1 to advertise the loopback routes of PE1 to ASBR2, and then to PE2.

[*ASBR1] bgp 100
[*ASBR1-bgp] network 1.1.1.9 32
[*ASBR1-bgp] quit
[~ASBR1] commit

The configurations of PE2 and ASBR2 are similar to the configurations of PE1 and ASBR1 respectively. For configuration details, see Configuration Files in this section.

Establish an MP-EBGP peer relationship between PE1 and PE2.

# Configure PE1.

[~PE1] bgp 100
[*PE1-bgp] peer 4.4.4.9 as-number 200
[*PE1-bgp] peer 4.4.4.9 connect-interface LoopBack 1
[*PE1-bgp] peer 4.4.4.9 ebgp-max-hop 10
[*PE1-bgp] ipv4-family vpnv4
[*PE1-bgp-af-vpnv4] peer 4.4.4.9 enable
[*PE1-bgp-af-vpnv4] quit
[*PE1-bgp] quit
[*PE1] commit

# Configure PE2.

[~PE2] bgp 200
[*PE2-bgp] peer 1.1.1.9 as-number 100
[*PE2-bgp] peer 1.1.1.9 connect-interface LoopBack 1
[*PE2-bgp] peer 1.1.1.9 ebgp-max-hop 10
[*PE2-bgp] ipv4-family vpnv4
[*PE2-bgp-af-vpnv4] peer 1.1.1.9 enable
[*PE2-bgp-af-vpnv4] quit
[*PE2-bgp] quit
[*PE2] commit

Verify the configuration.

After the configurations are complete, the CEs can learn routes to each other's interface and can ping through each other.

The following example uses the command output on CE1.

[~CE1] display ip routing-table
Route Flags: R - relay, D - download to fib, T - to vpn-instance, B - black hole route
------------------------------------------------------------------------------
Routing Table: Public
         Destinations : 8        Routes : 8
Destination/Mask    Proto  Pre  Cost       Flags  NextHop         Interface
       10.1.1.0/24  Direct 0    0              D  10.1.1.1        GigabitEthernet0/1/0
       10.1.1.1/32  Direct 0    0              D  127.0.0.1       GigabitEthernet0/1/0
     10.1.1.255/32  Direct 0    0              D  127.0.0.1       GigabitEthernet0/1/0
      10.2.1.0/24  EBGP   255  0              D  10.1.1.2        GigabitEthernet0/1/0
      127.0.0.0/8   Direct 0    0              D  127.0.0.1       InLoopBack0
      127.0.0.1/32  Direct 0    0              D  127.0.0.1       InLoopBack0
127.255.255.255/32  Direct 0    0              D  127.0.0.1       InLoopBack0
255.255.255.255/32  Direct 0    0              D  127.0.0.1       InLoopBack0
[~CE1] ping 10.2.1.1
  PING 10.2.1.1: 56  data bytes, press CTRL_C to break
    Reply from 10.2.1.1: bytes=56 Sequence=1 ttl=252 time=102 ms
    Reply from 10.2.1.1: bytes=56 Sequence=2 ttl=252 time=89 ms
    Reply from 10.2.1.1: bytes=56 Sequence=3 ttl=252 time=106 ms
    Reply from 10.2.1.1: bytes=56 Sequence=4 ttl=252 time=104 ms
    Reply from 10.2.1.1: bytes=56 Sequence=5 ttl=252 time=56 ms
  --- 10.2.1.1 ping statistics ---
    5 packet(s) transmitted
    5 packet(s) received
    0.00% packet loss
    round-trip min/avg/max = 56/91/106 ms

ASBRs do not have VPNv4 routes. Run the display bgp routing-table label command on an ASBR. The command output shows the label information of the routes.

The following example uses the command output on ASBR1.

[~ASBR1] display bgp routing-table label
Total Number of Routes: 2
 BGP Local router ID is 2.2.2.9
 Status codes: * - valid, > - best, d - damped, x - best external, a - add path,
               h - history,  i - internal, s - suppressed, S - Stale
               Origin : i - IGP, e - EGP, ? - incomplete
 RPKI validation codes: V - valid, I - invalid, N - not-found
        Network           NextHop           In/Out Label
 *>     1.1.1.9           10.10.1.2         15360/NULL
 *>     4.4.4.9           10.21.1.2         15361/15361

Configuration Files

CE1 configuration file

#
 sysname CE1
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.1.1.1 255.255.255.0
#
bgp 65001
 peer 10.1.1.2 as-number 100
 #
 ipv4-family unicast
  undo synchronization
  import-route direct
  peer 10.1.1.2 enable
#
return

PE1 configuration file

#
 sysname PE1
#
ip vpn-instance vpn1
  route-distinguisher 100:1
  apply-label per-instance
  vpn-target 1:1 export-extcommunity
  vpn-target 1:1 import-extcommunity
#
 mpls lsr-id 1.1.1.9
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.10.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip binding vpn-instance vpn1
 ip address 10.1.1.2 255.255.255.0
#
interface LoopBack1
 ip address 1.1.1.9 255.255.255.255
#
bgp 100
 peer 4.4.4.9 as-number 200
 peer 4.4.4.9 ebgp-max-hop 10
 peer 4.4.4.9 connect-interface LoopBack1
 peer 2.2.2.9 as-number 100
 peer 2.2.2.9 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  peer 4.4.4.9 enable
  peer 2.2.2.9 enable
  peer 2.2.2.9 label-route-capability
 #
 ipv4-family vpnv4
  policy vpn-target
  peer 4.4.4.9 enable
#
 ipv4-family vpn-instance vpn1
  peer 10.1.1.1 as-number 65001
  import-route direct
#
ospf 1
 area 0.0.0.0
  network 1.1.1.9 0.0.0.0
  network 10.10.1.0 0.0.0.255
#
return

ASBR1 configuration file

#
 sysname ASBR1
#
 mpls lsr-id 2.2.2.9
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.10.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.21.1.1 255.255.255.0
 mpls
#
interface LoopBack1
 ip address 2.2.2.9 255.255.255.255
#
bgp 100
 peer 10.21.1.2 as-number 200
 peer 1.1.1.9 as-number 100
 peer 1.1.1.9 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  network 1.1.1.9 255.255.255.255
  peer 10.21.1.2 enable
  peer 10.21.1.2 route-policy policy1 export
  peer 10.21.1.2 label-route-capability
  peer 1.1.1.9 enable
  peer 1.1.1.9 route-policy policy2 export
  peer 1.1.1.9 label-route-capability 
#
ospf 1
 area 0.0.0.0
  network 2.2.2.9 0.0.0.0
  network 10.10.1.0 0.0.0.255
#
route-policy policy1 permit node 1
 apply mpls-label
route-policy policy2 permit node 1
 if-match mpls-label
 apply mpls-label
#
return

ASBR2 configuration file

#
 sysname ASBR2
#
 mpls lsr-id 3.3.3.9
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.40.1.1 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip address 10.21.1.2 255.255.255.0
 mpls
#
interface LoopBack1
 ip address 3.3.3.9 255.255.255.255
#
bgp 200
 peer 10.21.1.1 as-number 100
 peer 4.4.4.9 as-number 200
 peer 4.4.4.9 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  network 4.4.4.9 255.255.255.255
  peer 10.21.1.1 enable
  peer 10.21.1.1 route-policy policy1 export
  peer 10.21.1.1 label-route-capability
  peer 4.4.4.9 enable
  peer 4.4.4.9 route-policy policy2 export
  peer 4.4.4.9 label-route-capability 
#
ospf 1
 area 0.0.0.0
  network 3.3.3.9 0.0.0.0
  network 10.40.1.0 0.0.0.255
#
route-policy policy1 permit node 1
 apply mpls-label
route-policy policy2 permit node 1
 if-match mpls-label
 apply mpls-label
#
return

PE2 configuration file

#
 sysname PE2
#
ip vpn-instance vpn1
  route-distinguisher 200:1
  apply-label per-instance
  vpn-target 1:1 export-extcommunity
  vpn-target 1:1 import-extcommunity
#
 mpls lsr-id 4.4.4.9
 mpls
#
mpls ldp
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.40.1.2 255.255.255.0
 mpls
 mpls ldp
#
interface GigabitEthernet0/1/8
 undo shutdown
 ip binding vpn-instance vpn1
 ip address 10.2.1.2 255.255.255.0
#
interface LoopBack1
 ip address 4.4.4.9 255.255.255.255
#
bgp 200
 peer 1.1.1.9 as-number 100
 peer 1.1.1.9 ebgp-max-hop 10
 peer 1.1.1.9 connect-interface LoopBack1
 peer 3.3.3.9 as-number 200
 peer 3.3.3.9 connect-interface LoopBack1
 #
 ipv4-family unicast
  undo synchronization
  peer 1.1.1.9 enable
  peer 3.3.3.9 enable
  peer 3.3.3.9 label-route-capability
 #
 ipv4-family vpnv4
  policy vpn-target
  peer 1.1.1.9 enable  
#
 ipv4-family vpn-instance vpn1
  peer 10.2.1.1 as-number 65002
  import-route direct
#
ospf 1
 area 0.0.0.0
  network 4.4.4.9 0.0.0.0
  network 10.40.1.0 0.0.0.255
#
return

CE2 configuration file

#
 sysname CE2
#
interface GigabitEthernet0/1/0
 undo shutdown
 ip address 10.2.1.1 255.255.255.0
#
bgp 65002
 peer 10.2.1.2 as-number 200
 #
 ipv4-family unicast
  undo synchronization
  import-route direct
  peer 10.2.1.2 enable
#
return