I have a linksys wrt54gs wireless router. I have had it for almost 2 years, it has been hooked up to a DSL modem, no problems whatsoever. I just moved, and now have a Motorolla SB5101 cable modem.
I followed all of the steps exactly for setting up the router with a cable modem. Everything went smooth, when I check the status of the router, it has an IP address, everything's good. But I can't get online. The modem is fine, I'm hooked up right now via USB. The router is also fine, I can log into it and everything. All the lights are good on both the router and the modem. I downloaded and installed the latest firmware, I've power cycled, nothing. I know it has to be something simple, some setting somewhere.
My troubles started after I upgraded my WRT54G V2.0 to the latest firmware. The download firmware file is prefixed with WRT54GV4.0_ which leads me to question if it is supported to run on my WRT54G V2.0 machine.
The full name of the firmware binary in the Zip archive is "WRT54GV4.0_4.21.1.US_code.bin". Please confirm or correct that this is the latest & greatest firmware version for my V2.0 WRT54G.
The problem presents itself as an in-ability to connect to ot ping any IP device past the RF side of the Motorola SBV5120 Cable Modem (also an older Motorola SB4100).
I use DHCP on the Modem with OOL's (Optimum On-Line) DHCP Server, in turn I use DHCP on the Router with the Modem as DHCP server and finally use the Router as DHCP Server for my home network desk top/laptop/printservers/USB wireless hubs. Either the Router's MAC address or my laptop's MAC Address is reported in the SBV5120's configuration as CPE device, depending on which is connected. I can always connect to the internet by cabling my laptop directly to the bodem's Ethernet port instead of the Router's WAN-Internet-Link port.
According to OOL tech Support, The SBV5120 and downstream devices do not care about which MAC addresses is used, just that one is present. Apparently the ability of spoofing to defeate MAC Address Filtering worked, so they don't do it any more (My guess - let me know if I'm right or wrong)
The modem log consistently reports success in completing the DHCP process and reports itself as operational. After a series of power cycle of both modem and router, I was finally able to connect to the internet through the router. This lasted about 28 hours. If I connect the IP LAN port of my laptop, I can connect to the internet.
At this point, I found the firmware alternative, dd-WRT, and replaced the LinkSys firmware with the dd-WRT firmware. Consistent ability to connect to the inter has been the result. The Latest LinkSys firmware is in question. I hope they have a plan to fix it. If not, I'm going to look very closely at the alternatives when it comes time to purchase 11n products.
I had a very similar problem and here is how I got mine to work.
Equipment WRT54G v5, Motorola SB5101. using ethernet cable not USB.
I downloaded and upgraded to the latest firmware and cloned the MAC, performed all steps as shown to connect and it still wouldn't connect to the internet.
My eventual fix.
Go into the routers software and reset to factory defaults. Remember this will reset all of your passwords, network name, etc. Factory password "admin" Disconnected the router and connected the modem directly to the computer to gain internet access. Access Linksys website. Click on "support" then "technical support". Then go to "Easy Link Home Networking Tools" then "Easy Link Connect".
RUN the software (dont' save). Follow the directions.
I tried several different times to run the easy link connect software without resetting to factory defaults and it did not work. So make sure you reset to factory defaults. Also the disc included with the router would not work either. I hope this helps some people who have the same problem.