Created attachment 211337 [details]
ARIN and possibly other whois servers sometimes append a port number to the hostname in a referral, which whois(1) does not recognize.
This can be seen with one of freebsd.org's addresses, which includes a referral to NYI's whois servers on an alternate port:
% whois 126.96.36.199
Created attachment 211359 [details]
I posted a lightly modified version of the patch for review here: https://reviews.freebsd.org/D25156
A commit references this bug:
Date: Thu Jul 9 17:27:14 UTC 2020
New revision: 363052
whois: Handle referrals to rwhois servers.
Submitted by: email@example.com
Differential Revision: https://reviews.freebsd.org/D25156