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I'm having issue with installing a router/WAP behind another router (which goes to my ISP). Can you

Lisa, I was reading a Q&A by Graham and have a similar question. The WAP that the original post referred to was a Linksys BEFW11S4, which is actually a Router/WAP.

I am having a similar issue with installing a router/WAP behind another router (which goes to my ISP). PC's behind the WAP router can't see any of the PC's behind the ISP router (unless I use their IP address). Any advice you can give to configure these things so it looks like just one LAN behind the ISP router? Thank you.
I'm assuming that your configuration looks something like this:

 ISP--------BroadbandRouter------WirelessRouter | | EthernetPCs WirelessPCs

When you say that your Wireless PCs can't "see" your Ethernet PCs, I think you mean that you can't use Network Neighborhood to browse shared files and printers on these PCs. This occurs because you actually have two separate subnetworks rather than having one integrated LAN. NetBIOS LAN broadcasts are not passing through your wireless router.

One way to achieve what you want is to create this configuration:

 ISP--------BroadbandRouter------WirelessAP [not router] | | EthernetPCs WirelessPCs

Note that the AP does not route -- it just relays LAN frames between wireless and wired segments of the same subnetwork. NetBIOS broadcast traffic would automatically reach both LAN segments, allowing your Wireless PCs to browse named shares on Ethernet PCs and vice versa.

In LinkSys terminology, you really want a WAP11, not a BEFW11S4. Unfortunately, in most products, this is not a configurable choice -- it's a decision you make at time of purchase.

However, you might be able to accomplish this through cabling and configuration if either router has a built-in switch or hub with an Ethernet uplink port. If so:

  1. Unplug the Wireless Router's WAN port from your Broadband Router's Ethernet LAN.
  2. Plug the Wireless Router's Ethernet uplink port into an unused Ethernet port on your Broadband Router, or vice versa.
  3. Statically assign an unused IP from the Broadband Router's LAN to the Wireless Router's LAN interface.
  4. Disable the DHCP Server function on the Wireless Router so that Wireless PCs will look elsewhere on the LAN for dynamic IPs.
  5. Use the DHCP Server on your Broadband Router to give Wireless Clients dynamic IPs in the same subnet as your Ethernet PCs.

If this works, the WAN port on the Wireless Router and its routing and firewall functions will no longer be used. Instead, you will only use the AP and switch/hub in the Wireless Router. You will have created one big subnet, with all traffic routed through your Broadband Router.

If this doesn't work (for example, because neither router has an Ethernet uplink port), you have another alternative. You can configure "lmhosts" files on your Wireless PCs with the names and addresses of your Ethernet PCs, so that they can find those PCs by name and browse their shares. On Windows XP, start with the lmhosts.sam file located in the WINDOWSSYSTEM32DRIVERSETC folder. Follow examples in that sample file to create the necessary entries, then save as "lmhosts" (no .sam extension). You can either add the address of the domain controller (DC) for the entire workgroup or individual addresses of every PC you want to locate. Note that at least some static IP addressing is required for this solution to work.

This was last published in October 2003

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