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BGP between different AS numbers
http://forum.gns3.net/topic5155.html
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Author:  slimzee [ Sat Jul 21, 2012 2:55 pm ]
Post subject:  BGP between different AS numbers

Just playing around with GNS3 but I can't get ebgp with different? AS?

Why does this not bring up BGP?
Router 1:
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 3.3.3.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 65001
neighbor 2.2.2.2 update-source Loopback0
no auto-summary


Router 2:
router bgp 65001
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
neighbor 1.1.1.1 remote-as 65000
neighbor 1.1.1.1 update-source Loopback0
no auto-summary



why does this bring up BGP?
Router 1:
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 3.3.3.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 65000
no auto-summary

Router 2:

router bgp 65000
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
neighbor 1.1.1.1 remote-as 65000
neighbor 1.1.1.1 update-source Loopback0
no auto-summary

Author:  rednectar [ Sat Jul 21, 2012 10:06 pm ]
Post subject:  Re: BGP between different AS numbers

Example 1 is wrong because you are trying to to do eBGP between two devices that are not directly connected to each other.
AND you don't do eBGP between loopback addresses (normally)

Try a topology something like this: (This is still not complete though - I'll leave you with the challenge of actually getting network 3.3.3.0 advaertised)

Router1:1.1.1.1-----------1.1.1.2:Router2
Note:1.1.1.1 and 1.1.1.2 are DIRECTLY connected - they are not loopback addresses

Router 1:
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 3.3.3.0 mask 255.255.255.0
neighbor 1.1.1.2 remote-as 65001
no auto-summary


Router 2:
router bgp 65001
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
neighbor 1.1.1.1 remote-as 65000
no auto-summary


Example 2 is OK PROVIDED YOU HAVE ALREADY TESTED THAT 1.1.1.1 AND 2.2.2.2 CAN PING EACH OTHER
eg
Router1# ping 2.2.2.2 source lo0

If they can't ping each other, sort out your IGP then try again.

Key bgp ts commands:
show ip bgp summary
show ip bgp

Author:  rednectar [ Sat Jul 21, 2012 10:32 pm ]
Post subject:  Re: BGP between different AS numbers

Postscript:
You should check out Rene Molenaar's great labs at http://gns3vault.com/Labs/BGP/
Start with the IBGP lab and then the [urlhttp://gns3vault.com/BGP/ebgp-external-bgp.html]EBGP lab[/url]

Author:  delhi.pnr [ Sat Apr 20, 2013 9:21 am ]
Post subject:  Re: BGP between different AS numbers

Kindly Try below config, its because of ttl value..
+++++++++++++++++++++++++

Router 1:
router bgp 65000
no synchronization
bgp log-neighbor-changes
network 3.3.3.0 mask 255.255.255.0
neighbor 2.2.2.2 remote-as 65001
neighbor 2.2.2.2 ebgp-multihop
neighbor 2.2.2.2 update-source Loopback0
no auto-summary


Router 2:
router bgp 65001
no synchronization
bgp log-neighbor-changes
network 0.0.0.0
neighbor 1.1.1.1 remote-as 65000
neighbor 1.1.1.1 ebgp-multihop
neighbor 1.1.1.1 update-source Loopback0
no auto-summary

Nishant

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