Routers, like modems, can't be overclocked to achieve faster connect rates (or T1 rates, etc.). They theoretically can be overclocked to achieve faster computational rates such as packet decoding, access control list evaluation, etc. One possibility (and concern) is that the interface clocks are somehow bound to the processor clock. If they are, and you were successful in overclocking the processor, then you would end up with a very fast router that had no ability to connect to anything; the fairly accurate timing required to connect the various media types would be far out of spec.