Challenge 1

[rubel]

There are two possible answers.
Either this is done by mod_rewrite rule in httpd.conf file,
or by RedirectMatch rule set in .htaccess file.
Not sure about which one specifically, have not got time to do experiment with it!

[host.co.in]

There is something called canonical name entry and I am not sure if that should be kept on or off to fix this problem. Please come up with your suggestion on it with logical reasoning.

[Challenge]

You need to Set the following paramter in respective VirtualHost entry for that domain.

UseCanonicalName off

This will fix the problem.

[Admin1]

If you are accessing a directory under addon domain with http://addondomain.com/forum without trailing / and it is redirecting to
http:///sub.maindomain.com/forum/ and if you add trailing '/' at end i.e.http://addondomain.com/forum/, it is working fine. Why it is working with trailing '/' ?

[megha]

The probability is if you set
Use canonical name Off in Virtual Host entry, then it will be showing correctly as addondomain.com/forum/ and if you set
Use canonical name On in VirtaulHost entry, then it will go to sub.maindomain.com/forum. The canonical name should be set to "Off". Cannonical name is set to On ,when you want the addon domain to redirect to subdomainname.com.

Regards,
Megha.

If you are accessing a directory under addon domain with http://addondomain.com/forum without trailing / and it is redirecting to
http:///sub.maindomain.com/forum/ and if you add trailing '/' at end i.e.http://addondomain.com/forum/, it is working fine. Why it is working with trailing '/' ?