Even though the limit is applied before policy, the dropped prefixes don't count towards the limit. You can have a limit of 100 and receive 1000. If you drop 901 post policy, it will not kill the session, even when the limit is applied before policy. Thanks, Jakob.

Date: Sun, 22 Oct 2017 17:37:52 -0500 (CDT) From: Mike Hammett <nanog@ics-il.net>

Their device goes through prefix limit before prefix filter, so their filters wouldn't even see the advertisements as the prefix limit already killed the session. Raise the prefix limit so that the filters can get to work and now you're vulnerable to someone else injecting a ton of routes and melting their router.