umb(4) uses IF_WWAN_DEFAULT_PRIORITY (6); mention it in ifconfig(8). OK? (I considered more generic wording e.g. "wireless WAN interfaces", but that's inaccurate, this prio is only used for umb - wwan can also relate to some ppp/urndis/cdce interfaces which don't use this).
Index: ifconfig.8 =================================================================== RCS file: /cvs/src/sbin/ifconfig/ifconfig.8,v retrieving revision 1.358 diff -u -p -r1.358 ifconfig.8 --- ifconfig.8 24 Aug 2020 17:28:01 -0000 1.358 +++ ifconfig.8 17 Jan 2021 16:13:00 -0000 @@ -455,7 +455,10 @@ Set the interface routing priority to .Ar n is in the range of 0 to 15 with smaller numbers being better. The default priority of an interface is 0, -except for IEEE 802.11 wireless interfaces (priority 4) and +except for IEEE 802.11 wireless interfaces (priority 4), +.Xr umb 4 +interfaces (priority 6), +and .Xr carp 4 interfaces (priority 15). The default priority of newly connected routes (routes created by
