Non-root NIS client users cannot resolve username and groupname

Issue

• Non-root NIS client users cannot resolve usernames and groupnames. NIS server shows the following errors in /var/log/messages at the time:

  Dec 14 18:59:49 hostname ypserv[9935]: refused connect from 192.168.0.88:55748 to procedure ypproc_match (domain.example.com,passwd.byuid;-1)
  Dec 14 18:59:49 hostname ypserv[9935]: refused connect from 192.168.0.88:41960 to procedure ypproc_match (domain.example.com,passwd.byuid;-1)

When lookups are performed by the root user, they work fine.