Using our own DNS in xrumer

When I use xrumer now, I just add role to my server as a DNS server too. That way I do not count on "outside" DNS server.

I am still confused whether this actually help or not. Looks like it helps.

Anyway, basically, every time there is a host, say google.com my server do not need to make any connection asking what's the IP of google.com

It's cached right?

Can anyone confirm?

Thanks

Hope this helps