Filters BGP in ISP

[federico.arrua.261]

HI everyone. I have to configure filters in bgp routers to deny all /30 routes and routes with the ORIGIN incomplete( redistribute on bgp). How can i made that with access-list? or i have to used prefix-list?

[Philip D'Ath · Accepted solution]

I'm not completely sure of the answer.

I always use prefix lists.  I think a prefix like this would probably work to block /30's and /31's (it will only accept a prefix length of 29 or less).  In this case, I am matching what I want, and relying on the default "deny" to drop everything else.

ip prefix-list block_30_31 seq 5 permit 0.0.0.0/0 le 29

I'm not sure how to match "origin incomplete", but you can use the route-map command "match source-protocol".  So if you match every source protocol you expect to use, that should automatically result in unknown origins being dropped.

(config-route-map)#match source-protocol ?
 bgp Border Gateway Protocol (BGP)
 connected Connected
 eigrp Enhanced Interior Gateway Routing Protocol (EIGRP)
 isis ISO IS-IS
 lisp Locator ID Separation Protocol (LISP)
 mobile Mobile routes
 ospf Open Shortest Path First (OSPF)
 ospfv3 OSPFv3
 rip Routing Information Protocol (RIP)
 static Static routes

[federico.arrua.261]

The first answer works perfect,thanks!. The second one doesn't work because when i use match source-protocol, the routes with origin incomplete have source protocol bgp.

I found that i can use match origin igp and egp, so i can accept routes with those origins and discard the incomplete.

Thanks for the help!

[Philip D'Ath]

It would be great if you could rate and mark helpful responses.  :-)

[Jason M.]

It's pretty easy to do in XR using a route policy but I'm assuming you're talking about IOS. Would it be possible for you to tag the routes during redistribution or add a community to them? If so, you can just match those with a route map.