05-19-2012 02:58 AM - edited 03-04-2019 04:24 PM
Hello Guys,
Here is my network topology.
R1 and R2 are in the same AS which is 100. OSPF is configured as well as IBGP.
R4 and R6 are in the same AS which is 200. OSPF is configured as well as IBGP.
The problem is that I'm not able to ping from R2 to 1.0.0.1. It's reachable only toR6 serial.
Can any one please help.
R1 configuration
hostname R1
!
!
interface Serial1/1
ip address 10.0.0.50 255.255.255.252
ip nat inside
no sh
!
interface Serial1/0
ip address 1.0.0.37 255.255.255.252
ip nat outside
no sh
!
router ospf 1
network 10.0.0.48 0.0.0.3 area 0
!
router bgp 100
no synchronization
bgp log-neighbor-changes
neighbor 10.0.0.49 remote-as 100
neighbor 10.0.0.49 update-source Serial1/1
neighbor 10.0.0.49 next-hop-self
neighbor 1.0.0.38 remote-as 200
neighbor 1.0.0.38 ebgp-multihop 2
neighbor 1.0.0.38 update-source Serial1/0
no auto-summary
!
R2 configuration
hostname R2
!
!
interface fa2/0
ip address 10.0.0.1 255.255.255.240
no sh
interface Serial1/0
ip address 10.0.0.49 255.255.255.252
no sh
!
interface Serial1/1
ip address 10.0.0.53 255.255.255.252
no sh
!
router ospf 1
network 10.0.0.0 0.0.0.15 area 0
network 10.0.0.48 0.0.0.3 area 0
network 10.0.0.52 0.0.0.3 area 0
!
router bgp 100
neighbor 10.0.0.50 remote-as 100
neighbor 10.0.0.50 update-source s1/0
neighbor 10.0.0.50 next-hop-self
R4 configuration
hostname R4
!
!
interface fa2/0
ip address 1.0.0.17 255.255.255.240
no sh
interface Serial1/0
ip address 1.0.0.38 255.255.255.252
no sh
int s1/1
ip add 1.0.0.34 255.255.255.252
no sh
!
router ospf 1
network 1.0.0.16 0.0.0.15 area 1
network 1.0.0.32 0.0.0.3 area 1
!
router bgp 200
no synchronization
bgp log-neighbor-changes
neighbor 1.0.0.39 remote-as 100
neighbor 1.0.0.39 ebgp-multihop 2
neighbor 1.0.0.39 update-source Serial1/0
neighbor 1.0.0.33 remote-as 200
neighbor 1.0.0.33 update-source s1/0
neighbor 1.0.0.33 next-hop-self
redistribute connected
redistribute ospf
no auto-summary
!
R6 configuration
hostname R6
!
!
!
interface fa2/0
ip address 1.0.0.1 255.255.255.240
no sh
!
interface Serial1/0
ip address 1.0.0.33 255.255.255.252
no sh
!
router ospf 1
log-adjacency-changes
network 1.0.0.0 0.0.0.15 area 1
network 1.0.0.32 0.0.0.3 area 1
!
router bgp 200
neighbor 1.0.0.34 remote-as 200
neighbor 1.0.0.34 update-source Serial1/0
neighbor 1.0.0.34 next-hop-self
Solved! Go to Solution.
05-19-2012 06:24 AM
No static route is needed as 1.0.0.0 is being advertised properly and is seen on R2 with correct next hop. All the networks are advertised and things should work. Lets us know by testing if ping is now successful.
Note: Other solution is Static route if configured on R1 (not on R2) and redistributed into bgp might work as well. Considering R4-R6 is not advertising it.
Thanks,
Nandan
05-19-2012 05:23 AM
Can you post your OSPF configurations and "sh ip bgp" from these routers?
05-19-2012 05:36 AM
Here they are.
05-19-2012 05:47 AM
You didn't actually post any output.
Sent from Cisco Technical Support iPad App
05-19-2012 05:50 AM
Looks like R2 has network 1.0.0.0/28 which it is redistributing. So It is getting preffered. Is there any loopback interface or physical interface on R2 which has network 1.0.0.0/28 and not shown in diagram?
check by "show ip route 1.0.0.0" on R2
So overall the thing is R1 is learning 1.0.0.0 from two BGP neighbors and R2 has this network sourced through redistribution and hence its not reaching the actual destination i.e R6 (locally sourced is preferred and it is only available bgp route )
Credits to John for asking relevant outputs
Thanks,
Nandan
05-19-2012 06:02 AM
Hi guys,
Here are the outputs again.
R1 OSPF/BGP
R1#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.0.0.53 0 FULL/ - 00:00:34 10.0.0.49 Serial1/1
R1#sh ip bgp
BGP table version is 9, local router ID is 10.0.0.50
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
*> 1.0.0.0/28 1.0.0.38 0 200 i
*> 1.0.0.16/28 1.0.0.38 0 0 200 ?
*> 1.0.0.32/30 1.0.0.38 0 0 200 ?
r> 1.0.0.36/30 1.0.0.38 0 0 200 ?
*> 10.0.0.0/28 10.0.0.49 65 32768 ?
*> 10.0.0.48/30 0.0.0.0 0 32768 ?
**********************************************************************************
R2 OSPF/ BGP
R2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.0.0.50 0 FULL/ - 00:00:37 10.0.0.50 Serial1/0
R2#sh ip bgp
BGP table version is 11, local router ID is 10.0.0.53
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
*>i1.0.0.0/28 10.0.0.50 0 100 0 200 i
*>i1.0.0.16/28 10.0.0.50 0 100 0 200 ?
*>i1.0.0.32/30 10.0.0.50 0 100 0 200 ?
*>i1.0.0.36/30 10.0.0.50 0 100 0 200 ?
r>i10.0.0.0/28 10.0.0.50 65 100 0 ?
r>i10.0.0.48/30 10.0.0.50 0 100 0 ?
************************************************************************************************
R4 OSPF / BGP
R4#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
1.0.0.33 0 FULL/ - 00:00:35 1.0.0.33 Serial1/1
R4#sh ip bgp
BGP table version is 10, local router ID is 1.0.0.38
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
r>i1.0.0.0/28 1.0.0.33 0 100 0 i
*> 1.0.0.16/28 0.0.0.0 0 32768 ?
*> 1.0.0.32/30 0.0.0.0 0 32768 ?
*> 1.0.0.36/30 0.0.0.0 0 32768 ?
*> 10.0.0.0/28 1.0.0.37 65 0 100 ?
*> 10.0.0.48/30 1.0.0.37 0 0 100 ?
**************************************************************************************************
R6 OSPF/BGP
R6#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
1.0.0.38 0 FULL/ - 00:00:31 1.0.0.34 Serial1/0
R6#sh ip bgp
BGP table version is 11, local router ID is 1.0.0.33
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
*> 1.0.0.0/28 0.0.0.0 0 32768 i
r>i1.0.0.16/28 1.0.0.34 0 100 0 ?
r>i1.0.0.32/30 1.0.0.34 0 100 0 ?
*>i1.0.0.36/30 1.0.0.34 0 100 0 ?
*>i10.0.0.0/28 1.0.0.34 65 100 0 100 ?
*>i10.0.0.48/30 1.0.0.34 0 100 0 100 ?
================================
I don't have any loopbacks configured in my network and there isn't any connected network to R2 with network ID 1.0.0.0.0/28.
and here is the output of sh iproute 1.0.0.0 on R2
R2#sh ip route 1.0.0.0
Routing entry for 1.0.0.0/8, 4 known subnets
Variably subnetted with 2 masks
Redistributing via bgp 100
B 1.0.0.0/28 [200/0] via 10.0.0.50, 00:05:39
B 1.0.0.16/28 [200/0] via 10.0.0.50, 00:25:53
B 1.0.0.32/30 [200/0] via 10.0.0.50, 00:25:53
B 1.0.0.36/30 [200/0] via 10.0.0.50, 00:25:53
05-19-2012 06:10 AM
In your previous output things looked different and now they changed
Previous Output:
Latest Output For R2:
R2#sh ip ospf neighbor
Neighbor ID Pri State Dead Time Address Interface
10.0.0.50 0 FULL/ - 00:00:37 10.0.0.50 Serial1/0
R2#sh ip bgp
BGP table version is 11, local router ID is 10.0.0.53
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
*>i1.0.0.0/28 10.0.0.50 0 100 0 200 i
*>i1.0.0.16/28 10.0.0.50 0 100 0 200 ?
*>i1.0.0.32/30 10.0.0.50 0 100 0 200 ?
*>i1.0.0.36/30 10.0.0.50 0 100 0 200 ?
r>i10.0.0.0/28 10.0.0.50 65 100 0 ?
r>i10.0.0.48/30 10.0.0.50 0 100 0 ?
---------------
Observe the next hop and bgp table version. Anyway my previous suggestion was based on first output that you gave.
Regards,
Nandan
05-19-2012 06:15 AM
I copied the configuration after I took out a statically configured route on R2 to 1.0.0.1 as I was trying to figure out the problem.
There is no need to have a static route, right?
05-19-2012 06:24 AM
No static route is needed as 1.0.0.0 is being advertised properly and is seen on R2 with correct next hop. All the networks are advertised and things should work. Lets us know by testing if ping is now successful.
Note: Other solution is Static route if configured on R1 (not on R2) and redistributed into bgp might work as well. Considering R4-R6 is not advertising it.
Thanks,
Nandan
05-19-2012 06:28 AM
Can't believe it. It worked
Thank you guys your help is really appreciated!
05-19-2012 06:42 AM
Thats good Jory
Thanks.
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