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New Member

BGP route advertisement

I am confused about which routes will a bgp speaker advertise to its bgp neighbors?

Will it advertise the bgp routes in routing table OR will it advertise the best routes from the bgp table (but not necessarily in routing table)?

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Accepted Solutions
Hall of Fame Super Blue

BGP route advertisement

Kashish

It advertises routes that are installed in the BGP table.  Whether they end up in the IP routing table is dependant on whether they are the best choice in terms of AD etc.

Note that a BGP router will not advertise a route if it does not have a route to the next hop.

Jon

Purple

BGP route advertisement

Hi,

it will advertise the best route in its BGP table and it will install this best path in the RIB unless it is known via another source with better AD.

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
3 REPLIES
Hall of Fame Super Blue

BGP route advertisement

Kashish

It advertises routes that are installed in the BGP table.  Whether they end up in the IP routing table is dependant on whether they are the best choice in terms of AD etc.

Note that a BGP router will not advertise a route if it does not have a route to the next hop.

Jon

Purple

BGP route advertisement

Hi,

it will advertise the best route in its BGP table and it will install this best path in the RIB unless it is known via another source with better AD.

Regards

Alain

Don't forget to rate helpful posts.

Don't forget to rate helpful posts.
New Member

BGP route advertisement

Thanks!!

I thought so, but in Troubleshooting IP Routing Protocols book by Cisco press, it is stated that bgp router will advertise its routes from routing table, so wanted to confirm that that was indeed wrong.

On page 668, this is what is written:

One rule that BGP follows when advertising prefixes to other neighbors is that the prefix being advertised must

exist in the routing table of the advertising router.

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