01-20-2014 02:59 AM - edited 03-04-2019 10:07 PM
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
Solved! Go to Solution.
01-20-2014 09:37 AM
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 ?
01-20-2014 10:18 AM
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
01-20-2014 10:25 AM
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
Please don't forget to rate any posts that have been helpful.
Thanks.
01-20-2014 09:20 AM
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
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