CE-PE Routing: Configuring using BGP - I
· There are many options for CE-PE routing.
· In this post, let me configure routing between CE-PE using protocol BGP
· In PE router, we need to enable BGP under address-family ipv4 vrf <VPN_NAME>
· In CE router, we need to enable BGP normally under ipv4 address-family.
· Let me take a basic topology to configure this:
VRF Configuration:
CE1-PE1 Link
CE1#show run int ser1/0
Building configuration...
Current configuration : 87 bytes
!
interface Serial1/0
ip address 10.1.13.1 255.255.255.0
serial restart-delay 0
end
CE1#
PE1#show run | begin ip vrf
ip vrf VPN_A
rd 100:1
route-target export 100:1
route-target import 100:1
!
PE1#show run int ser1/0
Building configuration...
Current configuration : 112 bytes
!
interface Serial1/0
ip vrf forwarding VPN_A
ip address 10.1.13.3 255.255.255.0
serial restart-delay 0
end
PE1#
PE1#ping vrf VPN_A 10.1.13.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.13.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 36/64/104 ms
PE1#
CE2-PE2 Link:
CE2#show run int ser1/0
Building configuration...
Current configuration : 87 bytes
!
interface Serial1/0
ip address 10.1.24.2 255.255.255.0
serial restart-delay 0
end
CE2#
PE2#show run | begin ip vrf
ip vrf VPN_A
rd 100:1
route-target export 100:1
route-target import 100:1
!
PE2#show run int ser1/0
Building configuration...
Current configuration : 112 bytes
!
interface Serial1/0
ip vrf forwarding VPN_A
ip address 10.1.24.4 255.255.255.0
serial restart-delay 0
end
PE2#
PE2#ping vrf VPN_A 10.1.24.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.1.24.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/47/80 ms
PE2#
Observation:
· CE1-PE1 link is up
· CE2-PE2 link is up
Configuring MPLS in the Core, between PE1-PE2:
PE1(config)#int ser1/1
PE1(config-if)#mpls ip
PE1(config-if)#
*Mar 1 03:25:17.079: %LDP-5-NBRCHG: LDP Neighbor 4.4.4.4:0 (1) is UP
PE1(config-if)#
PE2(config)#int ser1/1
PE2(config-if)#mpls ip
PE2(config-if)#
*Mar 1 01:58:25.191: %LDP-5-NBRCHG: LDP Neighbor 3.3.3.3:0 (1) is UP
PE2(config-if)#
Configuring OSPF as IGP between PE1-PE2:
PE1#show run | begin router ospf
router ospf 1
log-adjacency-changes
network 3.3.3.3 0.0.0.0 area 0
network 10.1.34.3 0.0.0.0 area 0
!
PE2#show run | begin router ospf
router ospf 1
router-id 4.4.4.4
log-adjacency-changes
network 4.4.4.4 0.0.0.0 area 0
network 10.1.34.4 0.0.0.0 area 0
!
PE1#ping 4.4.4.4
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 4.4.4.4, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 20/56/88 ms
PE1#
PE2#ping 3.3.3.3
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/56/76 ms
PE2#
Configuring BGP-(ebgp between CE-PE and vpnv4 ibgp between PE1-PE2)
CE1#show run | begin router bgp
router bgp 100
no synchronization
bgp router-id 1.1.1.1
bgp log-neighbor-changes
network 1.1.1.1 mask 255.255.255.255
neighbor 10.1.13.3 remote-as 200
no auto-summary
!
PE1#show run | begin router bgp
router bgp 200
bgp router-id 3.3.3.3
no bgp default ipv4-unicast
bgp log-neighbor-changes
neighbor 4.4.4.4 remote-as 200
neighbor 4.4.4.4 update-source Loopback0
neighbor 10.1.13.1 remote-as 100
!
address-family vpnv4
neighbor 4.4.4.4 activate
neighbor 4.4.4.4 send-community extended
exit-address-family
!
address-family ipv4 vrf VPN_A
neighbor 10.1.13.1 remote-as 100
neighbor 10.1.13.1 activate
no synchronization
exit-address-family
!
CE2#show run | begin router bgp
router bgp 100
no synchronization
bgp router-id 2.2.2.2
bgp log-neighbor-changes
network 2.2.2.2 mask 255.255.255.255
neighbor 10.1.24.4 remote-as 200
no auto-summary
!
PE2#show run | begin router bgp
router bgp 200
bgp router-id 4.4.4.4
no bgp default ipv4-unicast
bgp log-neighbor-changes
neighbor 3.3.3.3 remote-as 200
neighbor 3.3.3.3 update-source Loopback0
neighbor 10.1.24.2 remote-as 100
!
address-family vpnv4
neighbor 3.3.3.3 activate
neighbor 3.3.3.3 send-community extended
exit-address-family
!
address-family ipv4 vrf VPN_A
neighbor 10.1.24.2 remote-as 100
neighbor 10.1.24.2 activate
no synchronization
exit-address-family
!
CE1#show ip bgp sum
BGP router identifier 1.1.1.1, local AS number 100
BGP table version is 2, main routing table version 2
1 network entries using 120 bytes of memory
1 path entries using 52 bytes of memory
2/1 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 1 (at peak 2) using 32 bytes of memory
BGP using 452 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.13.3 4 200 118 120 2 0 0 01:42:13 0
CE1#
CE1#show ip bgp
BGP table version is 2, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
CE1#
PE1#show ip bgp all sum
For address family: VPNv4 Unicast
BGP router identifier 3.3.3.3, local AS number 200
BGP table version is 8, main routing table version 8
2 network entries using 280 bytes of memory
2 path entries using 136 bytes of memory
4/2 BGP path/bestpath attribute entries using 496 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
1 BGP extended community entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 2 (at peak 2) using 64 bytes of memory
BGP using 1024 total bytes of memory
BGP activity 3/1 prefixes, 4/2 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
4.4.4.4 4 200 23 23 8 0 0 00:18:16 1
10.1.13.1 4 100 121 119 8 0 0 01:43:06 1
PE1#
PE1#show ip bgp vpnv4 all
BGP table version is 8, local router ID is 3.3.3.3
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 100:1 (default for vrf VPN_A)
*> 1.1.1.1/32 10.1.13.1 0 0 100 i
*>i2.2.2.2/32 4.4.4.4 0 100 0 100 i
PE1#
PE1#ping vrf VPN_A 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 32/49/116 ms
PE1#
CE2#show ip bgp sum
BGP router identifier 2.2.2.2, local AS number 100
BGP table version is 2, main routing table version 2
1 network entries using 120 bytes of memory
1 path entries using 52 bytes of memory
2/1 BGP path/bestpath attribute entries using 248 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 1 (at peak 1) using 32 bytes of memory
BGP using 452 total bytes of memory
BGP activity 1/0 prefixes, 1/0 paths, scan interval 60 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
10.1.24.4 4 200 32 32 2 0 0 00:28:20 0
CE2#
CE2#show ip bgp
BGP table version is 2, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 2.2.2.2/32 0.0.0.0 0 32768 i
CE2#
PE2#show ip bgp all sum
For address family: VPNv4 Unicast
BGP router identifier 4.4.4.4, local AS number 200
BGP table version is 4, main routing table version 4
2 network entries using 280 bytes of memory
2 path entries using 136 bytes of memory
4/2 BGP path/bestpath attribute entries using 496 bytes of memory
1 BGP AS-PATH entries using 24 bytes of memory
1 BGP extended community entries using 24 bytes of memory
0 BGP route-map cache entries using 0 bytes of memory
0 BGP filter-list cache entries using 0 bytes of memory
Bitfield cache entries: current 2 (at peak 2) using 64 bytes of memory
BGP using 1024 total bytes of memory
BGP activity 2/0 prefixes, 2/0 paths, scan interval 15 secs
Neighbor V AS MsgRcvd MsgSent TblVer InQ OutQ Up/Down State/PfxRcd
3.3.3.3 4 200 24 24 4 0 0 00:19:29 1
10.1.24.2 4 100 32 32 4 0 0 00:28:44 1
PE2#
PE2#show ip bgp vpnv4 all
BGP table version is 4, local router ID is 4.4.4.4
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
Route Distinguisher: 100:1 (default for vrf VPN_A)
*>i1.1.1.1/32 3.3.3.3 0 100 0 100 i
*> 2.2.2.2/32 10.1.24.2 0 0 100 i
PE2#
PE2#ping vrf VPN_A 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/52/88 ms
PE2#
Observation:
· EBGP between CE1-PE1 and CE2-PE2 is up.
· IBGP between PE1-PE2 is up
· CE1 is advertising 1.1.1.1/32 into BGP and PE1 is able to ping it.
· CE2 is advertising 1.1.1.1/32 into BGP and PE2 is able to ping it.
Now, lets check the CE routers for the routes:
CE1(config-if)#do show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.13.0 is directly connected, Serial1/0
CE1(config-if)#
CE2#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.24.0 is directly connected, Serial1/0
CE2#
Observation:
· We don’t see any other customer site routesL
· CE1 is not getting CE2’s loopback 2.2.2.2/32
· CE2 is not getting CE1’s loopback 1.1.1.1/32
Lets see the BGP debugs in CE routers:
CE1#debug ip bgp updates
CE1#
CE1#clear ip bgp *
CE1#
*Mar 1 02:03:39.935: %BGP-5-ADJCHANGE: neighbor 10.1.13.3 Down User reset
*Mar 1 02:03:41.083: %BGP-5-ADJCHANGE: neighbor 10.1.13.3 Up
CE1#
*Mar 1 02:03:41.191: BGP(0): 10.1.13.3 rcv UPDATE w/ attr: nexthop 10.1.13.3, origin i, originator 0.0.0.0, path 200 100, community , extended community
*Mar 1 02:03:41.195: BGP(0): 10.1.13.3 rcv UPDATE about 2.2.2.2/32 -- DENIED due to: AS-PATH contains our own AS;
*Mar 1 02:03:42.111: BGP(0): 10.1.13.3 rcv UPDATE about 2.2.2.2/32 -- withdrawn
CE1#
CE2#debug ip bgp updates
CE2#clear ip bgp *
CE2#
*Mar 1 00:36:46.163: %BGP-5-ADJCHANGE: neighbor 10.1.24.4 Down User reset
CE2#
*Mar 1 00:36:47.355: %BGP-5-ADJCHANGE: neighbor 10.1.24.4 Up
CE2#
*Mar 1 00:36:56.791: BGP: Import walker start version 0, end version 1
*Mar 1 00:36:56.791: BGP: ... start import cfg version = 0
*Mar 1 00:36:57.599: BGP(0): nettable_walker 2.2.2.2/32 route sourced locally
CE2#
*Mar 1 00:37:08.031: BGP(0): 10.1.24.4 rcv UPDATE w/ attr: nexthop 10.1.24.4, origin i, originator 0.0.0.0, path 200 100, community , extended community
*Mar 1 00:37:08.035: BGP(0): 10.1.24.4 rcv UPDATE about 1.1.1.1/32 -- DENIED due to: AS-PATH contains our own AS;
CE2#
*Mar 1 00:37:18.135: BGP(0): 10.1.24.4 send UPDATE (format) 2.2.2.2/32, next 10.1.24.2, metric 0, path Local
CE2#
Observation:
· This is expected because of AS-PATH is working as loop prevention mechanism
· CE routers are denying the routes from other CE as they see their own AS number in the AS-PATH
· Very interesting, what to do now?????
· Don’t you worry, we have 2 ways to get the routes from other CE
· First method is to use AS-OVERRIDE in PE routers, so that PE router will change the AS number to its own while forwarding the updates to CE
· 2nd method is to use allowas-in option in CE routers, so that CE routers will ignore the same AS number in the AS-PATH
· Lets see the configuration of AS-OVERRIDE in PE routers:
PE1(config)#router bgp 200
PE1(config-router)#address-family ipv4 vrf VPN_A
PE1(config-router-af)#neighbor 10.1.13.1 as-override
PE1(config-router-af)#
*Mar 1 02:04:58.207: %BGP-5-ADJCHANGE: neighbor 10.1.13.1 vpn vrf VPN_A Down AS-override change
PE1(config-router-af)#
*Mar 1 02:04:59.923: %BGP-5-ADJCHANGE: neighbor 10.1.13.1 vpn vrf VPN_A Up
PE1(config-router-af)#
PE2(config)#router bgp 200
PE2(config-router)#address-family ipv4 vrf VPN_A
PE2(config-router-af)#neighbor 10.1.24.2 as-override
PE2(config-router-af)#
*Mar 1 00:38:44.259: %BGP-5-ADJCHANGE: neighbor 10.1.24.2 vpn vrf VPN_A Down AS-override change
*Mar 1 00:38:45.047: %BGP-5-ADJCHANGE: neighbor 10.1.24.2 vpn vrf VPN_A Up
PE2(config-router-af)#
Now, lets see the routing tables in CE routers:
CE1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 10.1.13.3, 00:01:31
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.13.0 is directly connected, Serial1/0
CE1#ping 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
CE1#
CE1#show ip bgp
BGP table version is 5, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*> 2.2.2.2/32 10.1.13.3 0 200 200 i
CE1#
CE2#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1 [20/0] via 10.1.24.4, 00:00:59
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 1 subnets
C 10.1.24.0 is directly connected, Serial1/0
CE2#
CE2#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
.....
Success rate is 0 percent (0/5)
CE2#
CE2#show ip bgp
BGP table version is 6, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 10.1.24.4 0 200 200 i
*> 2.2.2.2/32 0.0.0.0 0 32768 i
CE2#trac
Observation:
· Now, CE routers got the routes from other CE routers
· But ping failsL
· But, for the successful ping we must have routes from end-end path
· In this case, we don’t have the CE-PE serial links in the other CE
· Solution is to redistribute the CE-PE link into vrf BGP in PE routers
PE1(config)#router bgp 200
PE1(config-router)#address-family ipv4 vrf VPN_A
PE1(config-router-af)#redistribute connected
PE1(config-router-af)#
PE2(config)#router bgp 200
PE2(config-router)#address-family ipv4 vrf VPN_A
PE2(config-router-af)#redistribute connected
PE2(config-router-af)#
Now, let see the routing tables for CE routers:
CE1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 10.1.13.3, 00:19:49
10.0.0.0/24 is subnetted, 2 subnets
C 10.1.13.0 is directly connected, Serial1/0
B 10.1.24.0 [20/0] via 10.1.13.3, 00:19:49
CE1#
CE1#ping 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 72/125/196 ms
CE1#
CE2#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1 [20/0] via 10.1.24.4, 00:20:19
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 2 subnets
B 10.1.13.0 [20/0] via 10.1.24.4, 00:20:19
C 10.1.24.0 is directly connected, Serial1/0
CE2#
CE2#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 100/164/212 ms
CE2#
Observation:
· Now, CE routers have the route for the other CE-PE link
· CE1 is able to ping CE2’S loopback 2.2.2.2/32
· CE2 is able to ping CE1’s loopback 1.1.1.1/32
Now, let’s see the configuration for ALLOWAS-IN in CE routers:
PE1(config-if)#router bgp 200
PE1(config-router)#address-family ipv4 vrf VPN_A
PE1(config-router-af)#no neighbor 10.1.13.1 as-override
PE1(config-router-af)#
PE2(config-if)#router bgp 200
PE2(config-router)#address-family ipv4 vrf VPN_A
PE2(config-router-af)#no neighbor 10.1.24.2 as-override
PE2(config-router-af)#
CE1(config)#router bgp 100
CE1(config-router)#neighbor 10.1.13.3 allowas-in
CE1(config-router)#
CE2(config)#router bgp 100
CE2(config-router)#neighbor 10.1.24.4 allowas-in
CE2(config-router)#
CE1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
C 1.1.1.1 is directly connected, Loopback0
2.0.0.0/32 is subnetted, 1 subnets
B 2.2.2.2 [20/0] via 10.1.13.3, 00:01:05
10.0.0.0/24 is subnetted, 2 subnets
C 10.1.13.0 is directly connected, Serial1/0
B 10.1.24.0 [20/0] via 10.1.13.3, 00:01:33
CE1#show ip bgp
BGP table version is 27, local router ID is 1.1.1.1
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 0.0.0.0 0 32768 i
*> 2.2.2.2/32 10.1.13.3 0 200 100 i
r> 10.1.13.0/24 10.1.13.3 0 0 200 ?
*> 10.1.24.0/24 10.1.13.3 0 200 ?
CE1#
CE1#ping 2.2.2.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 2.2.2.2, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 104/157/228 ms
CE1#
CE2#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, 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, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
1.0.0.0/32 is subnetted, 1 subnets
B 1.1.1.1 [20/0] via 10.1.24.4, 00:02:39
2.0.0.0/32 is subnetted, 1 subnets
C 2.2.2.2 is directly connected, Loopback0
10.0.0.0/24 is subnetted, 2 subnets
B 10.1.13.0 [20/0] via 10.1.24.4, 00:02:58
C 10.1.24.0 is directly connected, Serial1/0
CE2#
CE2#show ip bgp
BGP table version is 27, local router ID is 2.2.2.2
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
r RIB-failure, S Stale
Origin codes: i - IGP, e - EGP, ? - incomplete
Network Next Hop Metric LocPrf Weight Path
*> 1.1.1.1/32 10.1.24.4 0 200 100 i
*> 2.2.2.2/32 0.0.0.0 0 32768 i
*> 10.1.13.0/24 10.1.24.4 0 200 ?
r> 10.1.24.0/24 10.1.24.4 0 0 200 ?
CE2#
CE2#ping 1.1.1.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 64/138/228 ms
CE2#
Observation:
· Now, CE routers have the route for the other CE-PE link
· CE1 is able to ping CE2’S loopback 2.2.2.2/32
· CE2 is able to ping CE1’s loopback 1.1.1.1/32
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