There is a Linksys wireless router (WRT54G) with the Internet going into the one of the 4 LAN switch plugs. Another line comes out and goes to a Cisco PIX router. One more line comes off of the LAN ports and plugs into the WAN port. I figured this would give wireless users public IPs to log into the Cisco PIX, but I cannot figure why the loopback from the LAN to the WAN port.
There is a Linksys wireless router (WRT54G) with the Internet going into the one of the 4 LAN switch plugs. Another line comes out and goes to a Cisco PIX router. One more line comes off of the LAN ports and plugs into the WAN port. I figured this would give wireless users public IPs to log into the Cisco PIX, but I cannot figure why the loopback from the LAN to the WAN port.
— Via the Internet
If I am understanding what you are trying to do correctly, your wiring should look something like this: the WAN cable from the Linksys WRT54G router should plug into one of the LAN ports of the PIX (assuming you have a model 501 with multiple LAN ports on the chassis). Other models may have multiple LAN ports depending on what feature cards have been installed. Make sure that the IP address range used by the Linksys router on the LAN side is different from what the PIX is using for its LAN ports. Although NAT (Network Address Translation) is being used by the Linksys, it may be a little confusing on troubleshooting if you haven’t dealt with it some. In this configuration, everyone who is coming into the WRT54G will show up as the same public IP address that the WRT54G gets from the DHCP server running in the PIX.
If you want to have everyone on a distinct address that you can see from the PIX, you’ll need to do the network wiring a bit differently. You can connect a cable from one of the LAN ports on the Linksys to a LAN port on the PIX. But first, disable the DHCP service running in the Linksys WRT54G as the PIX will be providing this service. Once you have the DHCP service in Linksys disabled, you can either do a release and renew on the network card in your computer or disable it and re-enable it.
If everything works correctly, you should now have an IP address assigned by the PIX. If you don’t get an address, you may have to re-enable the DHCP service on the Linksys and then configure a static route so that the workstations connecting via the Linksys can directly go onto your Internet connection via the PIX. With a regular Cisco switch, you could use the IP helper-address command to tell the switch you are on the forward the DHCP request. Unfortunately, that command isn’t available on the Linksys routers that I have worked with.
The first method above will be the easiest to implement and to troubleshoot where a problem arises. The second method is a little more involved and requires that you have some understanding of how IP routing works and how to do some troubleshooting when the need arises. In either case, take a few minutes beforehand to update the firmware in both boxes. Be sure to keep good documentation on how you set things up and why. This will be a good reference to consult when you have to figure out why there is a problem weeks or months down the road when you may not remember why you set things up the way you did.
