Hi all,

we experienced issues with non-functional BFD Sessions. Debugging yielded that bird does not use RFC compliant BFD Port ranges.
RFC 5881 states: "" The source port MUST be in the range 49152 through 65535. ""; however, the port range is not restricted within bird and thus using arbitrary high ports.
Some tier 1 transit providers like "Deutsche Telekom" apply strict filter for BFD and only allow RFC5881 compliant ports, hence the issue.

There is a workaround to limit the port range globally at system level (/proc/sys/net/ipv4/ip_local_port_range); this seems to work, but we have the strong feeling that restriction of port range for BFD sessions should happen within bird itself.

Kind regards,
Christian