From the ISP it connects to Netvanta 3120 router. The router connects to the WAN port of the Apple Airport Extreme wireless router that is set to bridge mode(the only way I could get it to work). The airport extreme has two wireless networks, a main and a guest. The guest network won't allow connection from any device.The default guest network that was setup by a different company used a default IP range. This is my setup:
Netvanta IP address and gateway 10.0.1.1
Airport extreme IP address 10.0.1.203
Main wireless network IP range 10.0.1.2 ...10.0.1.240
Guest wireless network IP range starts with 176.xxx.xxx.xxx
Do I need to make changes to the Netvanta or the Airport Extreme?
Without knowing a bit more about the Airport Extreme's configuration it's difficult to tell.
You may need to add a static route to 176.x.x.x in the 3120 to 10.0.1.203.
You may need to create two VLANs, one for main and one for guest on both the Airport and the Adtran.
By the way, unless you're routing public 176.x.x.x addresses assigned to you from your ISP to guests, you will probably want to renumber your guest network. Private addresses should be in the range 10.X.X.X, 172.16.X.X through 172.31.X.X, or 192.168.X.X. Otherwise you are going to blackhole part of the public Internet to your guest network.