I understand most of the bgp communities like no-advertise, no-export, etc., but our provider had us add a community full of numbers to workaround another provider advertising our address space. What do these numbers do exactly?
It's something like:
route-map set-community permit 10
match ip address 5
set community 528739922
I can only assume that they're putting a priority on this community in a route-map on their side and then making the other providers advertisement and lower priority. This was a cutover from a legacy system to a newer system with the legacy system let unmodified. It screwed up our routing last night, and it seems like this is what they did to fix it. I wasn't involved in this one, but I'm curious as to what the above route-map does.
If u add this line "ip bgp-community new-format" to ur box, u will see that the long number is actually community 8067:61010 so ur AS + tag for action.
Communities provide a tagging mechanism where you can group customers and treat their traffic accordingly.
Based on your community, the ISP is making traffic decision within their network and perhaps with other ISP carriers as well.
What type of routing decisions are made? Only the ISP can answer that.
Communities can be set both inbound or outbound. when done outbound (towards another AS) its purpose needs to be coordinated and agreed.
I think your neighboring AS knows about this community and is taking action...else what is the point of setting it outbound.