Any one can answer the BGP Synchronization question ?

davidy2001
davidy2001 used Ask the Experts™
on
Any one can answer the BGP Synchronization question ?

The topology is very simple. Router2---Router1--interface e1/1(ip address 111.1.1.1/24)

R1
router bgp 12
network 111.1.1.0 mask 255.255.255.0
 neighbor 2.2.2.2 remote-as 12
 neighbor 2.2.2.2 update-source Loopback0
router ospf 1
network 0.0.0.0 255.255.255.255 area 0

R2
router bgp 12
 synchronization
neighbor 1.1.1.1 remote-as 12
neighbor 1.1.1.1 update-source Loopback0
router ospf 1
network 0.0.0.0 255.255.255.255 area 0

R2#show ip bgp
   Network          Next Hop            Metric LocPrf Weight Path
* i111.1.1.0/24     1.1.1.1                  0    100      0 i

After R2 enabled synchronization, the network 111.1.1.0/24 in bgp table lost marker “>” in the bgp table.

Question:
In the case, synchronization rule means network 111.1.1.0/24 is inactive (meaning losing marker “>” ) in R2’ BGP table until this network goes into R2 via IGP. Now the network 111.1.1.0/24 already has gone into R2 via IGP. Why does the network 111.1.1.0/24 is still inactive in R2 BGP table after enabling synchronization in R2 ?
Comment
Watch Question

Do more with

Expert Office
EXPERT OFFICE® is a registered trademark of EXPERTS EXCHANGE®
View Solution Only
Teeshirt

Commented:
Your topology isn't desirable to enable synchronization.

You can disable synchronization if one of the following conditions is true:

- Your AS does not pass traffic from one AS to another AS.
- All the transit routers in your AS run BGP.
davidy2001

Author

Commented:
Thanks. No matter whether I connect other additional iBGP or EBGP router to Router2, or not, the effect should be the same. The network 111.1.1.0/24 must be active ( with marker ">") , and then it can travel to next EBGP. what i am concerned is why the network 111.1.1.0/24 is not active after enabling synchronization
Network Security Analyst
Commented:
You are speaking ibgp and ospf between R1 and R2.
What is result of "R2#show ip bgp x.x.x.x". It's "not synchronized"?


I got troubleshooting guide from iphelp



Refer Cisco Case Studies

Hope this help.
Regards
davidy2001

Author

Commented:
Great, thanks, phyohtetaung
If eBGP connect with R2, there two ways to let 111.1.1.0/24 reach the eBGP: 1, turn off synchronization at R2, 2, redistribute the route or publish it by igp though the route is marked with "r" in bgp table.

Do more with

Expert Office
Submit tech questions to Ask the Experts™ at any time to receive solutions, advice, and new ideas from leading industry professionals.

Start 7-Day Free Trial