Thanks for your reply. There is no redistribution applied. The BGP Neibhor statement contains route maps for in and out. The out route map has the prefix list
route map com-list permit 10 (Applied outbound)
match ip add prefix-list xxx
set community asn.xxx
but the in bound has only the match statement as above mentioned, and there is no redistribution for the above route map, though there are seperate route map for redistribution between routing protocols.
only BGP advertisements that has one BGP community value as specified in community-list 100 will be accepted from neighbor
To be noted multiple Community attributes can be associated to a BGP advertisement, the filter will accept routes with multiple BGP communities if one of them matches the community-list.
The fact that no set action is configured means that no BGP attribute manipulation is performed on accepted routes, and the route-map is used as filter framework to invoke the use of the community-list as filter rule.
In the above case of inbound route map with just match community-list 100 what will be expected result of the statement? will there be any local preference or any other attributes set by the upstream provider? Also since there is no prefix list or access list attached to the route-map will all the in bound routes from ISP will have the community list 100 (ASN:100) Mapped?
the result will be that BGP routes that have a BGP community value as per community list will be accepted with no changes to the BGP attributes. Local preference is not passed by upstream provider it has meaning and scope only within a single BGP AS ( for this the name). other attributes like MED are kept unchanged.
Also since there is no prefix list or access list attached to the route-map will all the in bound routes from ISP will have the community list 100 (ASN:100) Mapped?
no because it is a match statement not a set action if the route has no BGP community equal to one of those specified in ip community-list the route will be denied
if you want to set a community on received routes you need a different configuration
route-map SETCOM-INBOUND permit 10
! match commands if needed
set community ASN:100 additive
! adding the additive keyword allows to append the ASN:100 value to existing BGP communities, without it you will first remove all BGP communities and then set only the new value
Thanks for the detailed reply. So if there is an inbound route map like the one below with only match and without any set statement, then will it deny all the ip comming with community value of 100? This part is bit confusing, since i am not sure what ip packets will be denyed because of the below statement that is comming in.
Hi everyone, I would like to thank you in advance for any help you can provide a newcomer like myself!
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