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Weird router problem

beatle

beatle

Diamond Member
I'm not sure what's happened here, but I came home from work today to find my connection dead. I have a Linksys WRT54GS w/dd-wrt firmware v23 SP2 voip. It has been up with the same configuration for months with only the occasional reboot.

I found that I can ping my ISP's gateway, but all of their DNS servers have "destination host unreachable." I also found that I could browse and ping Yahoo.com by ip, but it was crushingly slow to load even the text portions of the site and would occasionally drop packets. My VOIP phone (through Voicepulse) gets a dial tone and is able to make phones ring, but the connection was so poor that I couldn't hear anything but an occasional blip or chirp. Of course, I've hard booted all devices. I also tried to connect to sites with another box on my network. This yielded the same symptoms as my primary desktop.

Short of reloading the firmware on my router, can you think of any other things to try? I'm reluctant to do that, as every time I reload it, I seem to have intermittant connection problems for a few days after the flash. After that, it seems to settle in and behave itself.
 
Take the router out of the picture. Try again. Same symptoms, call provider (could very well be a problem with your ISP).

You can also use the command nslookup from a command prompt to see if you are getting name resolution.
 
I'm able to get online without the router. I should have mentioned that. When I'm behind my router and use nslookup and connect to my router for DNS, it won't resolve anything. When I attempt to connect to my ISP's DNS servers with nslookup, I cannot connect.
 
Then something is wrong with the DNS resolver on the router. Try inputing your actuall ISP DNS servers on the client manuall. If still no go, still no nslookup I think a re-flash is in order.
 
Here's the odd thing: I cannot even PING my ISP's DNS servers from behind my router. This is not a problem when my desktop is hooked to the modem directly. Also, I get a completely different ip on a different subnet (72.192.x.x vs 68.227.x.x) with a direct connection. My desktop pulls the same DNS servers as my router, however. Releasing and renewing the IP on my router does nothing, as I get the same 68.227.x.x IP.
 
I know it sounds dumb....

Power everything off (including modem) for 30 minutes plus. Then bring up modem. Wait 10 minutes, bring up router, wait 10 minutes, bring up computer.

This will clear every state machine/table there is. It does sound like something is fubarred with the router code/software. Possibly a bit error.
 
Ok, I'll try that. The fact that I have no connectivity problems on this subnet makes me think it's more of a routing problem with the ISP on my old subnet, however.
 
Originally posted by: beatle
Ok, I'll try that. The fact that I have no connectivity problems on this subnet makes me think it's more of a routing problem with the ISP on my old subnet, however.
Click to expand...

Could be. Could be a dhcp problem on their end as well. It could be any number of different things, but it sounds for sure layer3 related.

But I'm not quite getting what you mean by getting a different ip on a different subnet. Are you saying that directly connected you get a consistent subnet/ip and with the router you get another? And this is consistent?

If so, then I'd call the provider anyway. They might be having a problem.
 
Yes, I get a different IP in a different subnet consistently with my desktop.

I did call the provider and after 30 minutes on my cell phone, the tier 2 guy escalated it. It took some creative talking to get them to escalate it after connecting my desktop directly "fixed" the problem. Unfortunately I couldn't talk to tier 3. 🙁
 
Well, you're kind of in a bind. From the provider side - "no trouble found". And they are correct, they can't in anyway be held responsible (nor could they afford it) for your home networking gear.

But it's still not clear....with the router you get a different IP network, consistently than you do without the router?

The determining factor is "can your subnet/dhcp assignment be directly tied to if you do or do not use the router?" And "Is this truly your external IP when using the router?"

It sounds like you know what you're looking for/at, I'm just asking for clarification. When you call support again, have the MAC addresses of your directly connected PC (it's NIC) and the WAN port of your router recorded and in hand. If you don't talk down to them and strictly speak with the facts, they may be able to help.

Start with layer1, work up to layer2, then to layer3, then to layer4, then up.
 
I know it doesn't make any sense, but yes, my desktop gets a different IP on a different network than my router does.

When I said "creative talking" I didn't necessarily mean "colorful language." 🙂 I was also tech support for a few years...
 
Originally posted by: beatle
I know it doesn't make any sense, but yes, my desktop gets a different IP on a different network than my router does.

When I said "creative talking" I didn't necessarily mean "colorful language." 🙂 I was also tech support for a few years...
Click to expand...

Well it makes perfect sense if some changes are going on.
 
Well the "cooling off" time seems to have done the trick. My router is still getting the same IP, as my DHCP lease probably didn't expire, but whatever it was has passed. Thanks, spidey!
 
I'm reviving this thread because the problem continues. Rebooting the router does not help. Rebooting the cable modem does not help. Shutting both down, then bringing up the cable and then the router will fix the problem every time. My cable modem is an old Motorola SB4200 if that matters. I'm not sure whether to fault the router or the cable modem at this point. I don't fancy replacing either just on a hunch.

Sometimes it'll be a month or so between failures (I had one on Tuesday) and sometimes it's days (I had one just a few minutes ago). Any suggestions other than to start throwing parts at the problem?
 
Cable came by yesterday and dropped off a new Scientific Atlanta modem and billed me for $40. I can take it back and get credit for it, but I'm not sure if this was actually the problem. He said he found nothing wrong with the line and that the cable modem was fine, it was just old and did not support DOCSIS 2.1 which this new one does. I'm a bit out of my element here.
 
Well, today my internet connection died again with the same symptoms, even with the new modem. It's too late to call tech support now, but it'd be nice to have some new ideas to troubleshoot with them tomorrow. Anyone else reading this thread?
 
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