Would someone be so kind as to explain why BGP speakers within a common AS need to be fully meshed please. I am reading some Cisco documentation that is attached to this message. The paragraphs in red are what is not quite clear to me. Thanks a lot. ________________________________________________________________________ Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
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Figure 12-2: Internal BGP Example
!Router A router bgp 100 neighbor 180.10.30.1 remote-as 100 neighbor 190.10.50.1 remote-as 100 neighbor 170.10.20.2 remote-as 300 network 150.10.0.0 !Router B router bgp 100 neighbor 150.10.30.1 remote-as 100 neighbor 175.10.40.1 remote-as 400 neighbor 180.10.30.1 remote-as 100 network 190.10.50.0 !Router C router bgp 400 neighbor 175.10.40.2 remote-as 100 network 175.10.0.0 !Router D router bgp 100 neighbor 150.10.30.1 remote-as 100 neighbor 190.10.50.1 remote as 100 network 190.10.0.0 When a BGP speaker receives an update from other BGP speakers in its own AS (that is, via IBGP), the receiving BGP speaker uses EBGP to forward the update to external BGP speakers only. This behavior of IBGP is why it is necessary for BGP speakers within an AS to be fully meshed. For example, in Figure 12-2, if there were no IBGP session between Routers B and D, Router A would send updates from Router B to Router E but not to Router D. If you want Router D to receive updates from Router B, Router B must be configured so that Router D is a BGP peer.
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