I have an "AirPort Extreme 802.11n (2nd Gen)" according to a serial number lookup here.
I am not sure if this is the same as MB053LL/A which is mentioned is this archived thread. (Couldn't find a way to lookup the part number + couldn't find the tech specs at apple.com.)
I was wondering if this base station has the capability to setup a guest network in addition to the primary network.
According to the above mentioned Apple Discussions thread, the base station needs to have simultaneous dual band operation capability to make this possible. (Since I couldn't find the tech specs, I'm not sure what this base station has.)
I would assume from this Knowledge Base Article that the 2nd generation AirPort Extreme is one generation too old: