bgpd supports up to 255 byte shutdown communications. So the manpage is not telling the truth. Also I don't think it is helpful to mention the limit at all. bgpctl will exit with 'shutdown reason too long' if the text is too long which is good enough. For best interop people should keep the shutdown message as simple and short as possible.
-- :wq Claudio Index: bgpctl.8 =================================================================== RCS file: /cvs/src/usr.sbin/bgpctl/bgpctl.8,v retrieving revision 1.92 diff -u -p -r1.92 bgpctl.8 --- bgpctl.8 27 Sep 2019 10:34:54 -0000 1.92 +++ bgpctl.8 19 Oct 2019 09:01:20 -0000 @@ -87,9 +87,6 @@ If a is provided, the .Ar reason is sent as Administrative Shutdown Communication to the neighbor. -The -.Ar reason -cannot exceed 128 octets. .Ar peer may be the neighbor's address, description or the word .Cm group @@ -108,9 +105,6 @@ If a is provided, the .Ar reason is sent as Administrative Shutdown Communication to the neighbor. -The -.Ar reason -cannot exceed 128 octets. .Ar peer may be the neighbor's address, description or the word .Cm group
