OcNOS-DC : Multi-Protocol Label Switching Guide : Multi-Protocol Label Switching Configuration Guide : Inter-AS VPN Option-B Configuration
Inter-AS VPN Option-B Configuration
• Inter-AS Option B is a more scalable solution compared to Option A. It does not require any VRFs on the ASBRs, it uses VPNv4 eBGP to exchange VPNv4 updates.
• Single interface to connect the ASBRs.
• Packets are sent labelled between the ASBRs.
• No need for VRFs on the ASBR.
• ASBRs must be directly connected.
• Scales better than Option A.
Topology
 
PE1
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 2.2.2.2/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#ip vrf vrf1
Create a new VRF named vrf1.
(config-vrf)#rd 1:1
Assign the route distinguisher (RD) value as 1:1.
(config-vrf)#route-target both 1:1
Import routes between route target (RT) ext-communities.
(config-vrf)#exit
Exit VRF mode.
(config)#interface xe22
Enter interface mode.
(config-if)#ip vrf forwarding vrf1
Bind the interface connected to the CE router with VRF vrf1.
(config-if)#ip address 10.1.1.2/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe20
Enter interface mode.
(config-if)#ip address 11.1.1.2/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 2.2.2.2
Configure OSPF router id same as loopback ip address.
(config-router)#network 2.2.2.2/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 11.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router LDP mode.
(config-router)#transport-address ipv4 2.2.2.2
Configure LDP transport address same as loopback address.
(config-router)#exit
Exit LDP mode.
(config)#interface xe20
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-if)#exit
Exit interface mode.
(config)#router bgp 65000
Enter BGP router mode.
(config-router)#bgp router-id 2.2.2.2
Configure BGP router-id.
(config-router)#neighbor 41.41.41.41 remote-as 65000
Configure PE2-ASBR1 as an iBGP peer.
(config-router)#neighbor 41.41.41.41 update-source lo
Update the source as loopback for iBGP peering with the remote PE2 router.
(config-router)#address-family vpnv4
Enter VPNv4 address family mode.
(config-router-af)#neighbor 41.41.41.41 activate
Activate the PE neighbor so that it can accept VPN IPv4 routes.
(config-router-af)#exit-address-family
Exit VPNv4 address family mode.
(config-router)#address-family ipv4 vrf vrf1
Enter the IPv4 address family for VRF vrf1.
(config-router-af)#redistribute connected
Redistribute connected route.
(config-router-af)#exit-address-family
Exit IPv4 VRF Address Family mode.
 
P1
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 31.31.31.31/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe21
Enter interface mode.
(config-if)#ip address 11.1.1.31/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#ip address 12.1.1.31/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 31.31.31.31
Configure OSPF router id same as loopback ip address.
(config-router)#network 31.31.31.31/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 11.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 12.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router LDP mode.
(config-router)#transport-address ipv4 31.31.31.31
Configure LDP transport address same as loopback address.
(config-router)#exit
Exit LDP mode.
(config)#interface xe21
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-router)#exit
Exit interface mode.
PE2-ASBR1
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 41.41.41.41/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe21
Enter interface mode.
(config-if)#ip address 20.1.1.41/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#ip address 12.1.1.41/24
Assign ipv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 41.41.41.41
Configure OSPF router id same as loopback ip address.
(config-router)#network 41.41.41.41/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 12.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router LDP mode.
(config-router)#transport-address ipv4 41.41.41.41
Configure LDP transport address same as loopback address.
(config-router)#exit
Exit LDP mode.
(config)#interface xe15
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-if)#exit
Exit interface mode.
(config)#interface xe21
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#exit
Exit interface mode.
(config)#router bgp 65000
Enter BGP router mode.
(config-router)#bgp router-id 41.41.41.41
Configure BGP router-id.
(config-router)#no bgp inbound-route-filter
Disable inbound route filter.
(config-router)#neighbor 2.2.2.2 remote-as 65000
Configure PE1 as an iBGP peer.
(config-router)#neighbor 2.2.2.2 update-source lo
Update the source as loopback for iBGP peering with the remote PE1 router.
(config-router)#neighbor 20.1.1.3 remote-as 65001
Configure eBGP neighbor with ASBR2.
(config-router)#address-family vpnv4
Enter VPNv4 address family mode.
(config-router-af)#neighbor 2.2.2.2 activate
Activate the PE neighbor so that it can accept VPN IPv4 routes.
(config-router-af)#neighbor 2.2.2.2 next-hop-self
Configure this to make the router the next hop for a BGP neighbor.
(config-router-af)#neighbor 20.1.1.3 allow-ebgp-vpn
Configure this to allow exchange of VPN updates between eBGP peers.
(config-router-af)#neighbor 20.1.1.3 activate
Activate the ASBR eBGP neighbor.
(config-router-af)#exit-address-family
Exit VPNv4 address family mode.
 
 
PE3-ASBR2
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 3.3.3.3/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe21
Enter interface mode.
(config-if)#ip address 20.1.1.3/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#ip address 21.1.1.3/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 3.3.3.3
Configure OSPF router id same as loopback ip address.
(config-router)#network 3.3.3.3/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 21.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router ldp mode.
(config-router)#transport-address ipv4 3.3.3.3
Configure LDP transport address same as loopback address
(config-router)#exit
Exit LDP mode.
(config)#interface xe15
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-router)#exit
Exit LDP mode.
(config)#interface xe21
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#exit
Exit interface mode.
(config)#router bgp 65001
Enter BGP router mode.
(config-router)#bgp router-id 3.3.3.3
Configure BGP router-id.
(config-router)#no bgp inbound-route-filter
Disable inbound route filter.
(config-router)#neighbor 5.5.5.5 remote-as 65001
Configure PE4 as an iBGP peer.
(config-router)#neighbor 5.5.5.5 update-source lo
Update the source as loopback for iBGP peering with the remote PE1 router.
(config-router)#neighbor 20.1.1.41 remote-as 65000
Configure eBGP neighbor with PE4.
(config-router)#address-family vpnv4
Enter VPNv4 address family mode.
(config-router-af)#neighbor 5.5.5.5 activate
Activate the PE neighbor so that it can accept VPN IPv4 routes.
(config-router-af)#neighbor 5.5.5.5 next-hop-self
Configure this to make the router the next hop for a BGP neighbor.
(config-router-af)#neighbor 20.1.1.41 allow-ebgp-vpn
Configure this to allow exchange of vpn updates between eBGP peers.
(config-router-af)#neighbor 20.1.1.41 activate
Activate the ASBR eBGP neighbor.
(config-router-af)#exit-address-family
Exit VPNv4 address family mode.
P2
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 40.40.40.40/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe21
Enter interface mode.
(config-if)#ip address 21.1.1.40/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#ip address 22.1.1.40/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 40.40.40.40
Configure OSPF router id same as loopback ip address.
(config-router)#network 40.40.40.40/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 21.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 22.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router LDP mode.
(config-router)#transport-address ipv4 40.40.40.40
Configure LDP transport address same as loopback address.
(config-router)#exit
Exit LDP mode.
(config)#interface xe21
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable ldp in interface.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-if)#exit
Exit interface mode.
 
 
PE4 Configuration
 
#configure terminal
Enter configure mode.
(config)#interface lo
Enter interface mode.
(config-if)#ip address 5.5.5.5/32 secondary
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#ip vrf vrf1
Create a new VRF named vrf1.
(config-vrf)#rd 1:1
Assign the route distinguisher (RD) value as 1:1.
(config-vrf)#route-target both 1:1
Import routes between route target (RT) ext-communities.
(config-vrf)#exit
Exit VRF mode.
(config)#interface xe22
Enter interface mode.
(config-if)#ip vrf forwarding vrf1
Bind the interface connected to the CE router with VRF vrf1.
(config-if)#ip address 30.1.1.5/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#interface xe15
Enter interface mode.
(config-if)#ip address 22.1.1.5/24
Assign the IPv4 address.
(config-if)#exit
Exit interface mode.
(config)#router ospf 1
Enter router OSPF mode.
(config-router)#ospf router-id 5.5.5.5
Configure OSPF router id same as loopback ip address.
(config-router)#network 5.5.5.5/32 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#network 22.1.1.0/24 area 0
Define the network on which OSPF runs and associate area id.
(config-router)#exit
Exit OSPF router mode.
(config)#router ldp
Enter router LDP mode.
(config-router)#transport-address ipv4 5.5.5.5
Configure LDP transport address same as loopback address.
(config-router)#exit
Exit LDP mode.
(config)#interface xe15
Enter interface mode.
(config-if)#label-switching
Enable label switching in interface.
(config-if)#enable-ldp ipv4
Enable LDP in interface.
(config-if)#exit
Exit interface mode.
(config)#router bgp 65001
Enter BGP router mode.
(config-router)#bgp router-id 5.5.5.5
Configure BGP router-id.
(config-router)#neighbor 3.3.3.3 remote-as 65001
Configure PE2-ASBR1 as an iBGP peer.
(config-router)#neighbor 3.3.3.3 update-source lo
Update the source as loopback for iBGP peering with the remote PE2 router.
(config-router)#address-family vpnv4
Enter VPNv4 address family mode.
(config-router-af)#neighbor 3.3.3.3 activate
Activate the PE neighbor so that it can accept VPN IPv4 routes.
(config-router-af)#exit-address-family
Exit VPNv4 address family mode.
(config-router)#address-family ipv4 vrf vrf1
Enter the IPv4 address family for VRF vrf1.
(config-router-af)#redistribute connected
Redistribute connected route.
(config-router-af)#exit-address-family
Exit IPv4 VRF Address Family mode.
 
Validation
PE1
#show ip route vrf vrf1 database
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
ia - IS-IS inter area, E - EVPN,
v - vrf leaked
> - selected route, * - FIB route, p - stale info
 
IP Route Table for VRF "vrf1"
C *> 10.1.1.0/24 is directly connected, xe22, 03:49:26
B *> 30.1.1.0/24 [200/0] via 41.41.41.41, 00:00:41
C *> 127.0.0.0/8 is directly connected, lo.vrf1, 03:50:18
 
PE1#show ip bgp vpnv4 all
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
 
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:1 (Default for VRF vrf1)
*> l 10.1.1.0/24 0.0.0.0 0 100 32768 ?
*>i 30.1.1.0/24 41.41.41.41 0 100 0 65001 ?
Announced routes count = 1
Accepted routes count = 1
Route Distinguisher: 1:1
*>i 30.1.1.0/24 41.41.41.41 0 100 0 65001 ?
Announced routes count = 0
Accepted routes count = 1
PE2-ASBR1
#show ip bgp vpnv4 all
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
 
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:1
*>il 10.1.1.0/24 2.2.2.2 0 100 0 ?
*> l 30.1.1.0/24 20.1.1.3 0 100 0 65001 ?
Announced routes count = 0
Accepted routes count = 2
 
#show ip bgp vpnv4 all summary
BGP router identifier 41.41.41.41, local AS number 65000
BGP table version is 4
2 BGP AS-PATH entries
0 BGP community entries
 
Neighbor V AS MsgRcv MsgSen TblVer InQ OutQ Up/Down State/PfxRcd
2.2.2.2 4 65000 168 171 4 0 0 00:29:03 1
20.1.1.3 4 65001 111 119 4 0 0 00:42:51 1
 
Total number of neighbors 2
 
Total number of Established sessions 2
PE3-ASBR2
#show ip bgp vpnv4 all
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
 
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:1
*> l 10.1.1.0/24 20.1.1.41 0 100 0 65000 ?
*>il 30.1.1.0/24 5.5.5.5 0 100 0 ?
Announced routes count = 0
Accepted routes count = 2
 
#show ip bgp vpnv4 all summary
BGP router identifier 3.3.3.3, local AS number 65001
BGP table version is 4
2 BGP AS-PATH entries
0 BGP community entries
 
Neighbor V AS MsgRcv MsgSen TblVer InQ OutQ Up/Down State/PfxRcd
5.5.5.5 4 65001 41 45 4 0 0 00:15:59 1
20.1.1.41 4 65000 115 118 4 0 0 00:43:58 1
 
Total number of neighbors 2
 
Total number of Established sessions 2
PE4
#show ip bgp vpnv4 all
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal, l - labeled
S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
 
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 1:1 (Default for VRF vrf1)
*>i 10.1.1.0/24 3.3.3.3 0 100 0 65000 ?
*> l 30.1.1.0/24 0.0.0.0 0 100 32768 ?
Announced routes count = 1
Accepted routes count = 1
Route Distinguisher: 1:1
*>i 10.1.1.0/24 3.3.3.3 0 100 0 65000 ?
Announced routes count = 0
Accepted routes count = 1
 
#show ip route vrf vrf1 database
Codes: K - kernel, C - connected, S - static, R - RIP, B - BGP
O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2,
ia - IS-IS inter area, E - EVPN,
v - vrf leaked
> - selected route, * - FIB route, p - stale info
 
IP Route Table for VRF "vrf1"
B *> 10.1.1.0/24 [200/0] via 3.3.3.3, 00:00:48
C *> 30.1.1.0/24 is directly connected, xe22, 03:46:38
C *> 127.0.0.0/8 is directly connected, lo.vrf1, 03:49:54
 
Gateway of last resort is not set