Hurricane Electric now supports "Never via route servers" (the peeringdb flag) as part of our route filtering algorithm. Using peeringdb, an ASN may indicate that its routes should never be learned via route servers. As a simple detection method, currently route servers are detected at run time when the first AS hop of a path does not match the peer AS. When checking a path learned from a route server each hop is checked to see if it has "Never via route servers" set to true. Here is an example of a route failing the "Never via route servers" check. 80.96.25.0/24,rejected,received AS path 9009 62350 from a route server and 62350 has indicated that it is never to be learned via route servers (peeringdb flag). This path was learned via the Balcan-IX route servers (this example may be gone by the time you look at it, or it may exist for a while): https://routing.he.net/index.php?cmd=display_filter&as=24745&af=4&which=reasons The "Never via route servers" filtering is part of the static prefix filter generation, which is responsible for the decision to accept a prefix.