3 BGP Network Statements

[Ibrahim Jamil]

Hi Freinds why these 3 BGP Network Statements ?? the 2nd one isn't enough to advertize all as its 10.0.0.0 router bgp 65112 bgp router-id 10.255.241.104 bgp log-neighbor-changes network 0.0.0.0 network 10.0.0.0 network 10.4.0.0 mask 255.252.0.0 thanks all

[Giuseppe Larosa · Accepted solution]

Hello Ibrahim,

BGP now has a default of no auto-summary.

This means that an exact match for the prefix is needed to advertise in BGP

Example:

router bgp 100

no auto-summary

network 10.0.0.0.0

network 10.4.0.0 mask 255.252.0.0

The first command advertises 10.0.0.0/8 only if the prefix is present in the IP routing table in any form.

The second command advertises 10.4.0.0/22 again if present in IP routing table.

BGP can advertise both if both are present in IP routing table, it does not think in a classful way.

The protocol is classless and looks for prefixes and their prefix lengths.

If you want to create an aggregate and to advertise only that you need

router bgp 100

aggregate-address 10.0.0.0 255.0.0.0 summary-only

Hope to help

Giuseppe

[Ibrahim Jamil]

thanks Giuseppe