Istvan_Rabai Mon, 03/24/2008 - 06:12
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In BGP, when you have an EBGP connection, the the next hop attribute for the learned routes is by default the interface ip address of the EBGP neighbor in the neighboring AS.

With the next-hop-self option, you can overwrite this default behavior on the BGP router in this AS.

If the BGP router within this AS advertises routes to the IBGP neighbors, then it will set the next hop attribute to its own inteface ip address.

This way the internal BGP routers will have routes in their routing tables with the next hop pointing to the edge BGP router within their AS, where they got the update from.

For IGP routing protocols, like EIGRP and OSPF, it is not necessary to learn the ip routes to the EBGP connection (that is to the EBGP neighbor), and routes from the internal AS will not be advertised to the neighbor AS (ISP for example).

I hope I wasn't too complicated :)




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