Help!About IBGP

[tianxi.luo]

Why did not 22.2.2.2 and 11.1.1.1  be select the best route between R1 and R2 with IBGP protocol ? They all have 1.1.1.1 and 2.2.2.2 route in IGP route table.

(under synchronization,don't suggest no synchronization)

R1:
router ospf 1
 network 1.1.1.1 0.0.0.0 area 0
 network 12.0.0.1 0.0.0.0 area 0
 

router bgp 1
 synchronization
 bgp router-id 1.1.1.1
 network 11.1.1.0 mask 255.255.255.0
 neighbor 2.2.2.2 remote-as 1
 neighbor 2.2.2.2 update-source Loopback0

show ip bgp
     Network          Next Hop            Metric LocPrf Weight Path
 *>  11.1.1.0/24      0.0.0.0                  0         32768 i
 * i 22.2.2.0/24      2.2.2.2                  0    100      0 ?
 * i 44.4.4.0/24      4.4.4.4                  0    100      0 4 i

show ip route ospf

      2.0.0.0/32 is subnetted, 1 subnets
O        2.2.2.2 [110/2] via 12.0.0.2, 00:15:43, FastEthernet1/0
      4.0.0.0/32 is subnetted, 1 subnets
O        4.4.4.4 [110/3] via 12.0.0.2, 00:15:43, FastEthernet1/0
      24.0.0.0/24 is subnetted, 1 subnets
O        24.0.0.0 [110/2] via 12.0.0.2, 00:15:43, FastEthernet1/0
      34.0.0.0/24 is subnetted, 1 subnets
O        34.0.0.0 [110/3] via 12.0.0.2, 00:15:43, FastEthernet1/0

==============================================================

R2:

router ospf 1
 network 2.2.2.2 0.0.0.0 area 0
 network 12.0.0.2 0.0.0.0 area 0
 network 24.0.0.1 0.0.0.0 area 0
!
router bgp 1
 synchronization
 bgp router-id 2.2.2.2
 redistribute connected route-map loop
 neighbor 1.1.1.1 remote-as 1
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 4.4.4.4 remote-as 4
 neighbor 4.4.4.4 ebgp-multihop 2
 neighbor 4.4.4.4 update-source Loopback0

route-map loop permit 10
 match interface Loopback22

show ip bgp
     Network          Next Hop            Metric LocPrf Weight Path
 * i 11.1.1.0/24      1.1.1.1                  0    100      0 i
 *>  22.2.2.0/24      0.0.0.0                  0         32768 ?
 *>  44.4.4.0/24      4.4.4.4                  0             0 4 i

==========================================================

R4:

router ospf 1
 network 4.4.4.4 0.0.0.0 area 0
 network 24.0.0.2 0.0.0.0 area 0
 
router bgp 4
 synchronization
 bgp router-id 4.4.4.4
 bgp log-neighbor-changes
 network 44.4.4.0 mask 255.255.255.0
 neighbor 2.2.2.2 remote-as 1
 neighbor 2.2.2.2 ebgp-multihop 2
 neighbor 2.2.2.2 update-source Loopback0

show ip bgp
     Network          Next Hop            Metric LocPrf Weight Path
 *>  22.2.2.0/24      2.2.2.2                  0             0 1 ?
 *>  44.4.4.0/24      0.0.0.0                  0         32768 i

[rosaho]

This discussion has been reposted from Cisco Support Community Olympics Trivia to the WAN, Routing and Switching community.

[Vinit Jain]

Hello

Could you please check the subnet mask of loopback11 and loopback 22. Is the loopback configured as /24 prefix or /32 prefix. Could you please share the whole config. 

Thanks

Vinit

[Vinit Jain]

Just noticed you have "synchronization" configured under your bgp. Issue the no synchronization command under BGP to disable synchronization. This will prevent BGP to check for iBGP routes in IGP.

Refer to teh below CCO Document for more details:

http://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/26634-bgp-toc.html#synch

Hope this clarifies.

Vinit