Solved: Re: IBgp issue - Page 2

feroz syed · ‎01-20-2014

AS 2 Ibpg configured with ospf, on Router 3 and Router 5 both ebgp routes appear in route table, but on R4 and R6 there is no Ebgp routes.Goal is need to ping from R1 to R2 loop back address.

R5

R5#sh ip bgp

BGP table version is 6, local router ID is 5.5.5.5

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

*>i1.1.1.1/32 3.3.3.3 0 100 0 1 i

*> 2.2.2.2/32 192.168.52.2 0 0 3 i

*>i192.168.13.0 3.3.3.3 0 100 0 1 i

r> 192.168.52.0 192.168.52.2 0 0 3 i

R5#sh ip route bgp

1.0.0.0/32 is subnetted, 1 subnets

B 1.1.1.1 [200/0] via 3.3.3.3, 00:26:14

B 192.168.13.0/24 [200/0] via 3.3.3.3, 00:26:14

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 192.168.52.2, 00:26:19

R5#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 3.3.3.3 next-hop-self

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

neighbor 192.168.52.2 remote-as 3

no auto-summary

R3

R3#sh ip bgp

BGP table version is 6, 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

*> 1.1.1.1/32 192.168.13.1 0 0 1 i

*>i2.2.2.2/32 5.5.5.5 0 100 0 3 i

r> 192.168.13.0 192.168.13.1 0 0 1 i

*>i192.168.52.0 5.5.5.5 0 100 0 3 i

R3#sh ip route bgp

1.0.0.0/32 is subnetted, 1 subnets

B 1.1.1.1 [20/0] via 192.168.13.1, 00:26:47

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [200/0] via 5.5.5.5, 00:26:47

B 192.168.52.0/24 [200/0] via 5.5.5.5, 00:26:47

R3#sh run | sec bp

R3#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

neighbor 5.5.5.5 next-hop-self

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

neighbor 192.168.13.1 remote-as 1

no auto-summary

R3#

R4

R4#sh ip bgp

BGP table version is 5, 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

* i1.1.1.1/32 192.168.13.1 0 100 0 1 i

* i2.2.2.2/32 192.168.52.2 0 100 0 3 i

* i192.168.13.0 192.168.13.1 0 100 0 1 i

* i192.168.52.0 192.168.52.2 0 100 0 3 i

R4#sh ip route bgp

R4#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

neighbor 6.6.6.6 remote-as 2

neighbor 6.6.6.6 update-source Loopback0

no auto-summary

R6#sh ip bgp

BGP table version is 5, local router ID is 6.6.6.6

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

* i1.1.1.1/32 192.168.13.1 0 100 0 1 i

* i2.2.2.2/32 192.168.52.2 0 100 0 3 i

* i192.168.13.0 192.168.13.1 0 100 0 1 i

* i192.168.52.0 192.168.52.2 0 100 0 3 i

R6#sh ip route bgp

R6#sh run | sec bgp

router bgp 2

no synchronization

bgp log-neighbor-changes

neighbor 3.3.3.3 remote-as 2

neighbor 3.3.3.3 update-source Loopback0

neighbor 4.4.4.4 remote-as 2

neighbor 4.4.4.4 update-source Loopback0

neighbor 5.5.5.5 remote-as 2

neighbor 5.5.5.5 update-source Loopback0

no auto-summary

R1

R1#sh 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

C 192.168.13.0/24 is directly connected, Serial1/0

2.0.0.0/32 is subnetted, 1 subnets

B 2.2.2.2 [20/0] via 192.168.13.3, 00:28:25

B 192.168.52.0/24 [20/0] via 192.168.13.3, 00:28:25

R1#sh ip ngp

^

% Invalid input detected at '^' marker.

R1#sh 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

*> 2.2.2.2/32 192.168.13.3 0 2 3 i

*> 192.168.13.0 0.0.0.0 0 32768 i

*> 192.168.52.0 192.168.13.3 0 2 3 i

R1#sh run | sec bgp

router bgp 1

no synchronization

bgp log-neighbor-changes

network 1.1.1.1 mask 255.255.255.255

network 192.168.13.0

neighbor 192.168.13.3 remote-as 2

no auto-summary

R2

R2#sh ip bgp

BGP table version is 5, 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

*> 1.1.1.1/32 192.168.52.5 0 2 1 i

*> 2.2.2.2/32 0.0.0.0 0 32768 i

*> 192.168.13.0 192.168.52.5 0 2 1 i

*> 192.168.52.0 0.0.0.0 0 32768 i

R2#sh ip route bgp

1.0.0.0/32 is subnetted, 1 subnets

B 1.1.1.1 [20/0] via 192.168.52.5, 00:29:29

B 192.168.13.0/24 [20/0] via 192.168.52.5, 00:29:29

R2#sh run | sec bgp

router bgp 3

no synchronization

bgp log-neighbor-changes

network 2.2.2.2 mask 255.255.255.255

network 192.168.52.0

neighbor 192.168.52.5 remote-as 2

no auto-summary

feroz syed · ‎01-20-2014

i forget to ask one thing, if middle router don't know about bgp routes then how r3 and r5 exchange their ebgp routes between as, it should came from r4 or r6 am right ?

Jon Marshall · ‎01-20-2014

It's what i described in the post where i made an error.

R3 and R5 learnt the EBGP routes via IBGP because you had an IBGP peering between R3 and R5. There is no direct connection between them but that is not a requirement of IBGP.

If in your original setup you had not setup an IBGP peering between R3 and R5 it would not have worked. This is because if an IBGP router receives a route from an IBGP peer it cannot then advertise that route to another IBGP peer.

So if R5 advertised 2.2.2.2 to R4 and R6 they cannot then advertise that route to R3. R3 knows about that route because you have an IBGP peering between R3 and R5.

The way round this IBGP rule, as i said before, is to either have a full mesh so every router has an IBGP peering with every other router or to use route reflectors which relax the rule about not being able to advertise routes between IBGP peers.

You can confirm this by running IBGP on all routers within that AS but do not setup an IBGP peering from R3 to R5.

Jon

paul driver · ‎01-20-2014

Hello

If R4-R6 routers are running OSPF only they are unaware of any bgp routes,

As Alian as suggested the R3 -R5 are running OSPF/BGP (ebgp &ibgp) but these routing processes are unaware of each other routes ( SIN routing)

So when you redistribute the specific bgp routes on R3 (1.1.1.1) - R5 (2.2.2.2) via a route-map into ospf then with your ibgp peering will have a valid path and reachability will be available.

However if you remove the ibgp peering between R3/R5 you will need to perform mutual redistribution on these routers to gain reachability.

@Alian

Somewhere I must of mis-interpreted the OP query as looking through it I see full IBGP hence my post -

Yes without full ibgp peering in the "core" network totally agree with the redistribution.

res

Paul

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Paul

Jon Marshall · ‎01-20-2014

Paul

At the risk of making yet another basic error in this post

I think the point was that the OP was asking what would he need to do if he turned off IBGP on R4 and R6.

You are totally correct in that if R4 and R6 were running IBGP it would work.

Jon