Not learning routes from far end router has the same BGP AS #

frank · ‎05-03-2004

All our remote sites are using AS # 65090 and connect to a MPLS clound with AS # 65000.

Inside the clound, I am seeing all routes from all remote sites, but for each remote site I am not seeing the routes from the other remote.

Is it because I have all the same AS # for remotes site? How can I solve this problem if I want to use the same AS #?

mmolina2 · ‎05-03-2004

"as-override" needs to be configured on the neighbor command for all PE's with sessions to remote sites:

neighbor x.x.x.x as-override

Good Luck !

frank · ‎05-03-2004

What is the miminun IOS for this command?

I got an invalid input when I type this command?

mmolina2 · ‎05-03-2004

I know you probably realize this already but you are attemtping the command in the "address-family ipv4 vrf xxxx" BGP context, correct ? If so, I don't know what the minimum IOS requirement is

frank · ‎05-03-2004

I heard of this command but couldn't find it from Cisco Web site???

I don't understand what do you mean by "address-family ipv4 vrf xxxx BGP context"

Can you provide a link for this as-override?

Thanks in advance.

mmolina2 · ‎05-03-2004

I have only configured this command in a PE/VRF environment (address-family ipv4 vrf xxxx). I honestly don't know if this command applies to non-address family implementations.

Georg Pauwen · ‎05-03-2004

Hello,

how are you remote sites interconnected ? Do they have IBGP neighbors configured ? How are they connected to the EBGP neighbor ? Can you post the configuration of the AS65000 router and one of the AS65090 routers ?

Regards,

Georg

olorunloba · ‎05-03-2004

BGP uses AS path to check for routing loops, hence with your sites configured with the same ASN, they will reject the routing update, as they will think it is a routing loop because of the same ASN number. MPLS deals with the issue by the PE replacing the ASN number in the routing updates with its own. The command to do this is as stated above, as-override. Things to note.

1. It is configured on the service provider network, on its PE router. If you are not in charge of this then, you need to inform him.

2. When configuring BGP sessions on the PE router, it establishes IPV4 session to CE, VPNV4 to other PE routers. The IPVA session to CE routers are configured using

router bgp wxyz

address-family ipv4 vrf abc

neighbor x.x.x.x as-override

3. The command has been available since 12.0(7)T

http://www.cisco.com/en/US/products/sw/iosswrel/ps1830/products_feature_guide09186a0080087b1f.html#1031061

frank · ‎05-06-2004

Thanks for the answer...

I put it in for the PE router but still not see the routes from remote.

Here is my config...

***** MPLS-Core *****

MPLS#sh run

...

!

ip vrf MPLS

rd 88:8888

!

router bgp 65000

no synchronization

bgp router-id 2.2.2.2

bgp cluster-id 3463597649

bgp log-neighbor-changes

redistribute connected

neighbor 159.24.186.6 remote-as 65090

neighbor 206.114.78.70 remote-as 65090

neighbor 206.114.78.78 remote-as 65090

neighbor 206.114.78.82 remote-as 65090

no auto-summary

!

address-family ipv4 vrf MPLS

neighbor 159.24.186.6 remote-as 65090

neighbor 159.24.186.6 activate

neighbor 159.24.186.6 as-override

neighbor 206.114.78.70 remote-as 65090

neighbor 206.114.78.70 activate

neighbor 206.114.78.70 as-override

neighbor 206.114.78.78 remote-as 65090

neighbor 206.114.78.78 activate

neighbor 206.114.78.78 as-override

neighbor 206.114.78.82 remote-as 65090

neighbor 206.114.78.82 activate

neighbor 206.114.78.82 as-override

no auto-summary

no synchronization

exit-address-family

!

MPLS#sh ip ro

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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

159.24.0.0/30 is subnetted, 1 subnets

C 159.24.186.4 is directly connected, Serial1/2

206.114.78.0/30 is subnetted, 3 subnets

C 206.114.78.80 is directly connected, Serial1/0

C 206.114.78.68 is directly connected, Serial1/3

C 206.114.78.76 is directly connected, Serial1/1

10.0.0.0/8 is variably subnetted, 5 subnets, 4 masks

B 10.1.16.0/22 [20/0] via 159.24.186.6, 00:06:27

B 10.128.0.0/16 [20/0] via 206.114.78.82, 00:06:27

B 10.80.192.0/24 [20/0] via 206.114.78.70, 00:06:28

B 10.80.193.0/24 [20/0] via 206.114.78.78, 00:06:28

B 10.80.162.0/23 [20/0] via 206.114.78.78, 00:06:28

165.179.0.0/24 is subnetted, 1 subnets

B 165.179.85.0 [20/0] via 159.24.186.6, 00:06:29

MPLS#

***** Remote *****

KEN#sh run

...

router bgp 65090

no synchronization

bgp log-neighbor-changes

network 0.0.0.0

redistribute connected

redistribute static

neighbor 159.24.186.5 remote-as 65000

no auto-summary

!

...

KEN#sh ip ro

Codes: C - connected, S - static, I - IGRP, 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, E - EGP

i - IS-IS, 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

159.24.0.0/30 is subnetted, 1 subnets

C 159.24.186.4 is directly connected, Serial0

206.114.78.0/30 is subnetted, 3 subnets

B 206.114.78.80 [20/0] via 159.24.186.5, 00:11:36

B 206.114.78.68 [20/0] via 159.24.186.5, 00:11:36

B 206.114.78.76 [20/0] via 159.24.186.5, 00:11:36

10.0.0.0/22 is subnetted, 1 subnets

C 10.1.16.0 is directly connected, Loopback0

165.179.0.0/24 is subnetted, 1 subnets

C 165.179.85.0 is directly connected, Loopback1

KEN#

olorunloba · ‎05-06-2004

From your post, the problem is not with the as-override. Note the following.

1. The connected serial interface between the PE and CE i.e. MPLS and Ken needs to be put in a vrf i.e.

int s1/2

ip vrf forwarding MPLS

ip add 159.24.186.5 255.255.255.252

2. You only need to define the neighbour at the address-family since it is not carrying vpnv routes.

3. Since I guess that the 10.80. network is the VPN routes, it imples you have not placed those routes and interfaces at their appropriate vrfs and vpns, they are showing up in the global routing table.

Try to reconfigure appropriately and see what happens,

frank · ‎05-07-2004

Once I add this command on PE router, all BGP neighbor are not established anymore.

Do I need ip vrf forwarding on both CE and PE routers?

I don't see this in our production routers?

olorunloba · ‎05-07-2004

No, just on the PE router. Note that you add the ip address after adding the ip vrf forwarding. Because adding the vrf forwarding removes any previously configured ip address. Check the link below, and compare the router bgp configuration part.

http://www.cisco.com/en/US/tech/tk436/tk798/technologies_configuration_example09186a0080093d4e.shtml