The intial topology is:
The initial GNS3 net and router configs are: GNS3 Initial configs and topology
The first step was configuring MPLS on each of the 4 provider routers:
The common configuration sets the label range for 999 labels relative to the router number.
mpls label range 1000 1999
mpls label protocol ldp
mpls ldp router-id Loopback 0
Under the common provider interfaces enable mpls:
int fa0/0
mpls ip
Once completed on each of the routers, display the neighbors for verification:
Example from R2:
R2#show mpls ldp neighbor
Peer LDP Ident: 1.1.1.1:0; Local LDP Ident 2.2.2.2:0
TCP connection: 1.1.1.1.646 - 2.2.2.2.22261
State: Oper; Msgs sent/rcvd: 37/38; Downstream
Up time: 00:23:47
LDP discovery sources:
FastEthernet0/0, Src IP addr: 192.168.12.1
Addresses bound to peer LDP Ident:
192.168.12.1 192.168.14.1 1.1.1.1
Peer LDP Ident: 3.3.3.3:0; Local LDP Ident 2.2.2.2:0
TCP connection: 3.3.3.3.23134 - 2.2.2.2.646
State: Oper; Msgs sent/rcvd: 35/35; Downstream
Up time: 00:21:10
LDP discovery sources:
FastEthernet1/0, Src IP addr: 192.168.23.3
Addresses bound to peer LDP Ident:
192.168.23.3 192.168.35.3 3.3.3.3
The next step is to configure BGP across the vpn backbone as indicated on the topology diagram. The PE will be AS 100 and the CE AS 200.
R3 BGP Cofiguration:
router bgp 100
no bgp default ipv4-unicast
bgp log-neighbor-changes
neighbor 4.4.4.4 remote-as 100
neighbor 4.4.4.4 update-source Loopback0
!
address-family vpnv4
neighbor 4.4.4.4 activate
neighbor 4.4.4.4 send-community both
neighbor 4.4.4.4 next-hop-self
exit-address-family
!
R4 BGP Configuration
router bgp 100
no bgp default ipv4-unicast
bgp log-neighbor-changes
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 update-source Loopback0
!
address-family vpnv4
neighbor 3.3.3.3 activate
neighbor 3.3.3.3 send-community both
neighbor 3.3.3.3 next-hop-self
exit-address-family
Verification of the BGP state between R3 and R4:
R3#show ip bgp vpnv4 all summary
BGP router identifier 3.3.3.3, local AS number 100
BGP table version is 1, main routing table version 1
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
4.4.4.4 4 100 6 6 1 0 0 00:02:29 0
Routers R5 and R6 run a typical public BGP connection
Example from R6:
router bgp 200
no synchronization
bgp log-neighbor-changes
network 172.16.0.0
neighbor 192.168.46.4 remote-as 100
no auto-summary
!
Next, create the VRF on R3 and associate it with the serial interface going to R5
ip vrf R5
rd 1:56
route-target export 1:500
route-target import 1:500
!
!
int s1/0
ip vrf R5
ip add 192.168.35.3 255.255.255.0
The BGP process on R3 needs to be modified to enable the neighbor under the vrf:
router bgp 100
address-family ipv4 vrf R5neighbor 192.168.35.5 remote-as 200
Now perform the same configuration on R4 to build the vrf to R6
ip vrf R6
rd 1:50
route-target export 1:500
route-target import 1:500
!
rd 1:50
route-target export 1:500
route-target import 1:500
!
router bgp 100
address-family ipv4 vrf R6neighbor 192.168.46.6 remote-as 200
neighbor 192.168.46.6 activate
Verify reachability on R4 of the Loopback on R6
R4#ping vrf R6 172.16.0.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.0.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 1/25/76 ms
The final step is to allow the routes back into the AS on the customer routers. The default BGP behavior is to not accept BGP routes from the AS to enter the AS on an EBGP connection.
On R5 and R6, modify the BGP configuration:
R6
router bgp 200
neighbor 192.168.46.4 allowas-in
R5
router bgp 200
neighbor 192.168.35.3 allowas-in
This completes the lab example. Router 6 is and Router 5 are now able to ping each other sourcing from their loopback interfaces.
Final router configurations: Final Configs
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