jamie.baddeley(a)vpc.co.nz wrote:
Was pondering the impact of path-stuffed networks being announced into the APE combined with operators not actually setting APE learnt routes with a higher local pref.
In other words, how many operators out there are not preffing up APE learnt routes?
Definitely can cause issues - especially with RS learned paths, given they inherently have an extra AS in the AS_PATH. When you can see one path via APE and one via domestic transit with the same AS_PATH length, the domestic transit can win if the local-pref is the same, if people are using the Cisco new-default of longest-up-bgp-session as deterministic, rather than peer-id, in which case APE should win. While I no longer peer; I previously had a local-pref policy of: 200 : customer 175 : private peering 170 : public peering 150 : domestic transit 130 : international transit and just for fun, tagged each route with communities indicating where it was learned from, type, geo area, and so on. This comes in useful. Another fun issue can be people applying inconsistent local-pref policies between IXPs (e.g. WIX & APE), causing all sorts of fun weirdness! YMMV. aj.