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): 220.127.116.11 rcv UPDATE w/ attr: nexthop 18.104.22.168, origin i, originator 0.0.0.0, path 2 1, community , extended community
*Mar 1 00:04:07.971: BGP(0): 22.214.171.124 rcv UPDATE about 126.96.36.199/8 -- 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?