Hi there
I found unknown DNS names on RB2011 cache as show below
can any one explain is that an issue or what?

For me, the real problem is you who don't understand the screenshot you made yourself.
(thanks for specifying whether or not you put the asterisks,
and thanks for leaving the dots ... so we can't see the whole name)

For example, to you, is the domain %3d known or unknown?

Ignoring that you haven't shown how the router is configured,
so there may be requests coming from outside as well,
check your internal machines if they make weird requests ...
RouterOS alone does not make these requests, it could possibly depend on scripts or "CRLs" installed in the router.

(thanks for specifying whether or not you put the asterisks,

No sir i didn't put any asterisks .and there's no

I userd RB1100 as hotspot for providing internet to clients across NanoStation M2 access points ,

No answer?