UNIX/Linux: X11 connection rejected because of wrong authentication

 % ssh -X -l userid remotehost

remotehost% /usr/openwin/bin/xclock
X11 connection rejected because of wrong authentication.
X connection to localhost:10.0 broken (explicit kill or server shutdown).

If you encounter X11 connection rejected because of wrong authentication error after logging to an UNIX/Linux host through ssh with X11 forwarding option, -X, check your /etc/inet/hosts file for multiple localhost entries; and remove the unnecessary ones.

For example, my /etc/inet/hosts has the following entries when the xclock failed with an X11 connection rejected .. error.

remotehost% cat /etc/inet/hosts

127.0.0.1       localhost       
::1     localhost       
10.2.211.150    sunfiret2000      loghost

Removing the 2nd line, ::1 localhost, fixed the issue.
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