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Any one can answer the BGP Synchronization question ?
Any one can answer the BGP Synchronization question ?
The topology is very simple. Router2---Router1--interfa
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 ?
The topology is very simple. Router2---Router1--interfa
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 ?
RoutersNetworkingNetwork Architecture
Last Comment
davidy2001
ASKER
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
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ASKER
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.
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.
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.