This seems to be quite a common problem going by the number of posts on the subject in this community, you could try setting your x box to a static IP address and then turn it off, then login to the smarthub and remove the Xbox from the list of network devices and then restart both. You may also need to set a firewall rule to open port 3075 to the xbox.
In that case, assuming the Xbox is set for dynamic IP, it won't have an IP address. The dhcp server is part of the router, so that message basically tells you that the Xbox is not connected to your router. You may need to check your connection method but before you do, make sure you turn off smart wireless as suggested by @Devon_Dave.
If you're using an old router to provide an additional wireless access point then you will probably have two DHCP servers on the network which will cause problems and you will have to disable one of them