Linksys befsx41 Password

Long story short, I need to hack a Linksys befsx41 so I can view the activity logs.
A former employee set up his own subnet (including unsecured wireless) within our network, so he could sit in his car after hours and access the network with his laptop.
The router is running dhcp, but I can't get to the admin interface when I try to go to the IP address of the dhcp server.

Well the first thing here is to shut it down, if its a former employee then you don't want them accessing the network anymore.

Next, do you need to actually access the logs or simply shut it off and leave it ? You can generally do a factory reset on these things to reset the password but i am unsure if the logs will go, it'll probably be worth e-mail linksys to find out what happens to the logging if its reset.