Any one expert with routers/modems please help ?

[GTB]

The issue is based on how you configured and wired the Apple Airport Extreme device.

Note that both the Linksys Router (LR) and the Apple Airport Extreme Router (AR) are routers. Each has a WAN or Internet (whichever name the maker likes to call it) and few LAN ports. Being both are routers they have the ability to do NAT (network access translation, DHCP (dynamic host configuration protocol), and they have to be on different subnets and most of this is enabled right out of the box.

I do not know how you configured it but this is what you should do:

1. On LR, note the router IP address (probably something like 192.168.0.1 or 192.168.1.1; the subnet mask (most likely 255.255.255.0) the DHCP pool range (number of IP addresses in the pool, where it starts, where it ends), and the DHCP lease lifetime. Connect a wired cat5 connection from pc to LR LAN port. On LR, make sure you have some IP addresses not in the DHCP pool (let's say you have 20 devices you want to connect; I suggest you give yourself 50 addresses in the DHCP pool and use 192.168.1.100 - 192.168.1.150 if you are using the 192.168.1.0/24 subnet. Change the DHCP life time to 12 hours. Change the wireless channel from auto to manual and select channel 1. Save the settings. Note the wireless configuration (encryption type, ssid, preshare key, etc).

2. Connect the cat 5 wired cable to AR Lan port next and log onto AR. Disable DHCP entirely. Change wireless channel to channel 11. Change wireless settings to be the same as it is for the LR except for channel number. Change IP address to static, and I suggest using 192.168.1.2 if LR is 192.168.1.1. Save settings.

3. Now connect a CAT5 cable from LAN port of LR to a LAN (not WAN or Internet) port of AR. Power down both LR and AR for at least 3 minutes. Turn on LR and at least 3 minutes later turn on AR. At this time you can connect wired and wireless devices. Make sure any LAN devices with static LAN IP addresses are revised to accommodate the retirement of the AR subnet. Now configure wireless devices to use the SSID, encryption type. preshare key, etc of LR and make sure it connects while in LR range. Once successful, walk to the AR range and it should connect and all devices should communicate to each other as you are now on same subnet and have one DHCP server.