Unable to get online with 169.254 address
 

I've got a Linksys WRT54G with the 2.2 firmware and a Smart AX MT882 modem which I had been using fine until I found that the security settings (the router had been using WPA) had been reset and I had an unsecured access point, still don't know why.

I tried to reset the encryption on the router and put the device passwords back which seemed to go OK but now I can't get online. I've confirmed that the router can see the modem and a Vista laptop (not mine) can connect to the AP with limited access but can't connect to the Internet through it. The only clue I have is the DHCP address being issued being a 169.254 address (I've also seen this on a Mac connected directly to the router). The DHCP server on the modem is configured to give out 192.168 addresses, does anyone know what may be causing this?

An address in the 169.254 range is a default fallback that Windows and Mac OS use when DHCP fails. It is not a valid IP, and you won't be able to route it to the internet with your current network setup.

Does the router offer any error reporting? Is DHCP enabled in the router configuration?

I've tried using the Router for DHCP and disabling it on the modem but to no avail, the router and modem have some basic logging but I've not been able to see anything useful in what has been output.

Additional details I forgot: when assigning a static IP in the DHCP range I've configured on the modem to the computers I still can't get out. Also, when connecting over wifi, I can't ping the IP addresses for the modem or router even though I'm connected to the AP.

OK, I've found that if I plug directly into the modem, enable the DHCP server and cut out the Router altogether I can get a DHCP lease. I also found that one of the entries under LAN settings where you can configure the IP addresses for the Ethernet and USB interfaces clashed with the IP address of the router-which probably wasn't helping.

I've also found that disabling the DHCP server on the modem and just using the router for DHCP gives an IP address but I still can't get online despite disabling anything that looks remotely like a security setting for good measure. Any ideas are welcome.

If I understand you correctly, your network setup is like this:

Internet ---- Modem ------ Router ------ Computer

Is that right? And I'm assuming that you want the router to act as the DHCP server? Or don't you care which one is the DHCP server? And have you tried navigating by IP address? So can you get to http://75.126.162.205 if you can't get to http://www.linuxquestions.org ?

What I would do in this situation is just use the modem DHCP server, and turn off the router DHCP server. If the modem is plugged into the router's WAN port, the router should get a valid IP address from the modem, and then pass through any later DHCP request.

Yep.
Does it make any difference? If not I'm not particularly worried as long as it works.
Good idea, I'll try that next.
That's the plan. I don't know if it's the best way to do it but it's been working fine previously.

It is more of a personal preference thing than anything else. I prefer to have only one DHCP server on my network just to cut down on the confusion if something goes wrong. Now that said, given your setup, you could have two running as long as the modem only connects to the router, and everything else goes through the router DHCP server (assuming you want your LAN to be running on a single set of IP addresses).

I think what you probably need to do at this point is make sure you understand where the problem is. The navigating by IP will help figure out if it is a DNS problem or not. From what you've posted so far, it almost looks like the modem doesn't have a good connection to the internet. I'd connect a computer directly to the modem and use it as the DHCP server and see if you can get out. If not, you need to gather some evidence, namely the output of the following commands:

ifconfig (to check and see if the computer is getting a valid IP address?)

route -n (to check and see if the gateway is properly set. The IP address in the gateway column should be the LAN IP address of your modem.)

the contents of your /etc/resolv.conf file. (To check and see if DHCP is providing a name server properly)

Connecting Computer> Router > Modem > Internet I can't get through using wither a URL or IP address, however, connecting Computer> Modem > Internet I can connect to websites using both. I seem to be getting valid DHCP addresses from each, anyone have any idea what's going on here?

It sounds like the router is broken.

Either stress junkie is right and the router is broken, or the communications between the router and the modem are borked. The way to check this would be to look at the WAN IP address of the router (when connected to the modem) and see if it is consistent with the IP addresses being handed out by the modem. You also might try a different network cable between the router and the modem, maybe that is broken (unless you have evidence to the contrary).
When the router is in the mix, is the router's DHCP server turned off? If it is, that pretty much shoots down the theory that the communications are borked and makes the faulty router idea more likely. Of course if a Windows laptop can still function normally with the router in place, that definitely makes for some serious weirdness.

As i was thinking about this a bit more, it might be helpful to have the following from both network configurations:

- output of ifconfig
- output of route -n
- contents of /etc/resolv.conf