Hi, You can try to delete AS-TRANSIT from the path and get first. Something like (this is just a sketch): delete(bgp_path, AS-TRANSIT).first ~ BOGON_ASNS On Mon, Mar 25, 2019 at 9:50 PM Robert Scheck <bird@robert-scheck.de> wrote:
Hello folks,
can I somehow import filter only on the 2nd AS number in the AS path? I know with the snippet below (heavily inspired by bgpfilterguide.nlnog.net), I can filter on AS numbers that appear somewhere in the AS path, however this import filter catches by nature also some pseudo-legitimate networks.
define BOGON_ASNS = [ 0, 23456, 64496..64511, 64512..65534, 65535, 65536..65551, 65552..131071, 4200000000..4294967294, 4294967295 ];
if (bgp_path ~ BOGON_ASNS) then { print "Detected bogon AS path: ", net, " ", bgp_path, ", (neighbour ", from, ")"; }
There are unfortunately some transits with broken export filters which e.g. export their DSL/FTTC and FTTH networks using private ASNs and I would like to explicitly filter these (example path: AS-TRANSIT AS-BOGON1 AS-BOGON2).
The documentation has hints for first and last ASN in path, but this would catch in above example only AS-TRANSIT or AS-BOGON2, but not AS-BOGON1. Any pointers?
Thank you.
Regards, Robert