Problem with WAN DHCP on old Linksys WRT54GSv4

[Ichinisan]

To summarize: What would be different about DHCP from one cable ISP versus DHCP from another?

I talked to someone yesterday with an old WRT54GS (v4) that could not get an IP address. I've seen some Linksys routers that show "0.0.0.0" on the internal status page when DHCP fails, but this one was just blank / empty where it should show the IP address. Strangely, the correct subnet mask, gateway, and DNS does appear. The owner said it worked fine with the previous ISP (Brighthouse Cable in FL). What would be different about the new ISP (my employer, a small cable ISP in GA) that would prevent this router from pulling an automatic / DHCP address?

All router settings appeared to be factory default (SSID: "linksys" / WiFi unsecured / default IP & subnet / default config password). We did a factory reset anyway, just in case the settings were corrupted.

In my system, I could see that a device with a Cisco-Linksys MAC ID had requested an IP and our system had assigned one. I had the customer try cloning a different MAC onto the router and that MAC appeared in our system and we assigned a different IP to it...but the router still wouldn't go online and still wouldn't show an IP on the internal Status page.

I had the person enter a manual / static IP for now and it works online. Apparently, Linksys doesn't keep the old firmware updates around because their site says there are no firmware downloads for this one. This model was very popular, so I'm fairly certain that firmware updates used to be available to download.

I advised the person to get a new router. Even a cheap Belkin for $30 from Target would be wireless-N and would come pre-configured with WiFi security out-of-the-box.

 

[cubby1223]

Sounds dumb, but have you power cycled the cable modem? If it's one that hands out the single public ip address, they often remember the mac address of the device that it was handed out to, and doesn't hand it out to anything else unless power cycled.

 

[alkemyst]

Sounds dumb, but have you power cycled the cable modem? If it's one that hands out the single public ip address, they often remember the mac address of the device that it was handed out to, and doesn't hand it out to anything else unless power cycled.

QFT...there is not going to be another ARP so the old mac address is locked in usually.

 

[Ichinisan]

Sounds dumb, but have you power cycled the cable modem? If it's one that hands out the single public ip address, they often remember the mac address of the device that it was handed out to, and doesn't hand it out to anything else unless power cycled.

Yes. I'm aware of the CPE limit. We did power cycle it.

The ISP I work for actually allows 2 public IPs. That makes it easier when we need to bypass a router for testing because we don't always have to reboot the modem. Some of our commercial customers use a switch with 2 devices off that so they can have 2 public IPs all the time.

Charter has CPE_Limit=1...so the modem always has to be rebooted when equipment is changed at my mother's place.