BGP attributes and extended communities

[carl_townshend]

Hi all

Can anyone please briefly explain what these are? I know the attributes are like the metric, but what about the exteneded commnuites, what are they used for?

and also I hear many things about the atrributes, what metrics does BGP use by default to select routes, is it the number of AS paths it has to cross? what if they are in the same AS, what metrics does it use ?

cheers

Carl

[Konstantin Dunaev]

selection algorithm:

http://www.cisco.com/en/US/customer/tech/tk365/technologies_tech_note09186a0080094431.shtml

extended communities are used in MPLS/VPN for exchange of VRF routing information.

[milan.kulik]

Hi,

read this regarding BGP communities included extended ones:

http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_6-2/bgp_communities.html

Here is the BGP route selection algorithm:

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

HTH,

Milan