BGP - updates back to the originator?

littlegrave · ‎11-20-2007

Hello,

I am a little bit confused regarding when BGP peers send a routing update back to the originator. I tried different scenarios and noticed that in some of them the eBGP neighbor sends back a routing update back to the local router and in some cases it does not. Could you please clarify when this should happen and why?

When I debugged bgp updates (debug ip bgp updates), I noticed the following (this is an update sent back to the originator):

*Mar 1 00:04:07.959: BGP(0): 15.0.0.5 rcv UPDATE w/ attr: nexthop 15.0.0.5, origin i, originator 0.0.0.0, path 2 1, community , extended community

*Mar 1 00:04:07.971: BGP(0): 15.0.0.5 rcv UPDATE about 113.0.0.0/8 -- DENIED due to: AS-PATH contains our own AS;

The results from the sniffed packets do not show any community or extended community attribute in the path attributes.

Could you please clarify the cause for this result?

Thank you.

Regards,

Pavel

markausten · ‎11-20-2007

The BGP peer sending the route back may be a Juniper router, this is normal operation for them, or a Cisco router with peer-groups configured or update-groups in operation.

http://www.cisco.com/en/US/products/sw/iosswrel/ps5207/products_feature_guide09186a00801d3b32.html