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As far as my understanding goes, RFC3021 is unsupported on some router devices widely used as it doesn't have a broadcast and network address and is therefore i
by fusl 7y ago
As far as my understanding goes, RFC3021 is unsupported on some router devices widely used as it doesn't have a broadcast and network address and is therefore invalid (/s), so some ISPs default to /30 instead for peering and don't filter out their peering networks in BGP.
- kbirkeland 7y agoI think the reason for using /30s instead of /31s is mostly legacy. It's a 19 year old standard and most vendors support it. Regardless of the point-to-point subnet used for the local peering connection, it's interesting that that many /30s have leaked into the default-free zone. BCP 194 recommends filtering IPv4 prefixes longer than a /24.