I can't see some sites via wi-fi.

October 6, 2007 1:19 PM

DD-WRT wireless access question: why can I connect to some sites when I'm wired into the router but not able to access those same sites when I'm connected via wi-fi?

I clicked on the first two links of the biggest suspension bridge post this morning (link 1 and link 2) and immediately get "Firefox can't establish a connection to the server at www.antara.co.id." I get the same result using Safari.

I notice the same thing when trying to connect to Homestead and Furniture Today Strangest thing though, when I connect via my XP box that's wired in, I see the sites just fine. My mac (via wi-fi) can't even run traceroutes on those sites: I get a "no route to host" message. I can run traceroutes on biggies like yahoo.com and stuff, and I can get to other sites just fine, as I'm posting this from the wireless computer in question.

My router is running DD-WRT v23 SP2. The only port forwarding and QoS deals I got going on relates to the windows/wired box. Wireless setup on the router is pretty plain jane with WPA enabled.

This is driving me bananas. Any idea what is going on? Is there some network setting in my mac that I jacked up?

posted by Tacodog to technology (15 comments total)

When you do a hostname lookup, what do you see for the domains you can't get at? Do they match with what nslookup on the XP box returns?
posted by chengjih at 1:27 PM on October 6, 2007

I had that exact same problem with DD-WRT, except the seemingly "forbidden" sites would change from time to time. My router eventually went belly up, and when I replaced it I kept the standard Linksys firmware, and haven't had any problems since.
posted by bjork24 at 1:27 PM on October 6, 2007

I, too, had similar issues with DD-WRT, specifically with YouTube videos. But it wasn't limited to a single OS - OS X, XP Pro and Debian all just sat there. Once I switched back to Linksys, no problem. Couldn't figure it out, either...
posted by cdmwebs at 1:36 PM on October 6, 2007

I've had similar problems with DD-WRT as well. Instead of going back to stock firmware, I went to Tomato because I wanted some of the extra features. Haven't had a problem since.
posted by Dipsomaniac at 1:40 PM on October 6, 2007 [1 favorite]

chengjih: running nslookup on yahoo.com (which I have no problems reaching on either machine) and www.antara.co.id (one of the sites in question) gives identical addresses on both the wireless mac and the wired xp box.
posted by Tacodog at 1:40 PM on October 6, 2007

My assumption would be that your DNS lookups are different for some reason. Try 'ping hostname' (subtitute the real hostname) and see if the IP address is the same on both your Mac and your Windows machine.

If they're different, you need to determine why. Most likely, the two machines aren't using the same DNS servers. Do an 'ipconfig /all' at the command prompt in Windows, and compare the information you see with your Network control panel on the Mac. You'll probably see that the DNS addresses are different. If they are, check that both machines are set to automatically get DNS info from DHCP.

If they already are, and you're still getting different DNS servers, then you probably have your network configured in a strange way, and it will take more troubleshooting.
posted by Malor at 2:27 PM on October 6, 2007

Oops, I didn't see that last answer, I'm sorry.

What happens if you plug the Mac in wired?
posted by Malor at 2:27 PM on October 6, 2007

I had tons of issues with DD-WRT, then some kind soul in a previous AskMe thread much like this recommended Tomato, as Dipsomaniac has already done.

I've never looked back. Tomato is THE FUCKING BALLS. Really.
posted by Civil_Disobedient at 3:07 PM on October 6, 2007

Ah, I didn't realize DD-WRT had so many problems. And now that you mention it cdmwebs, I have experienced that youtube problem before. I thought it was a problem on youtube's side all along.

I'll switch over to Tomato and get back to y'alls with the results. Thanks!
posted by Tacodog at 4:18 PM on October 6, 2007

I've had similar--but not exactly the same--issues with DD-WRT. I've had some success by lowering my MTU from 1500 to 1400. It is worth a try.
posted by joelr at 4:43 PM on October 6, 2007

I think there are some very strange and hard-to-diagnose MTU problems that can crop up with DD-WRT and very particular combinations of ISPs and websites / netpaths.

Basically, the MTU is the 'size' of the packets you send out. You want this to be as big as possible, but some communications links will drop packets if they're too big. ATM connections, in particular, can be weird about MTU size (they have additional headers or something that make the max MTU smaller than other methods, I guess? Feel free to educate me here...). There is a whole process that exists to 'feel out' the max MTU that a connection can take without dropping packets, for exactly this reason.

However, sometimes this process doesn't work right. In that case, you can send out packets that have an MTU that's too big for a particular 'hop' in a connection, and they get dropped, and it seems like you just can't connect to a webserver.

There are ways to figure out where the dropping is occurring, if you're curious (using traceroute and ping with various MTUs), but the easy solution is to reduce your MTU in the DD-WRT settings until things work. Or get a different router firmware.

Slightly offtopic ... there seem to be troubles in paradise for DD-WRT; I don't know what the real story is, but there are some nasty accusations going around between the developers. Anyone depending on it (particularly if you're thinking about it for future deployments) might want to keep an eye out for alternatives, and monitor the situation.
posted by Kadin2048 at 9:17 PM on October 6, 2007

Ok, this is strange. So I'm now running Tomato. Tried the below with MTUs of 1500 and 1400. nslookup for yahoo.com and www.antara.co.id gives the same results on my xp/wired box, mac/wireless and mac/wired. Yet even when I wired into my router with the mac, I still can't see the above links.

ping antara.co.id
PING antara.co.id (202.134.4.18): 56 data bytes
ping: sendto: No route to host

I'm still getting the same results. Is something in my network utility not set right? I'm suspecting DNS problems but I can see other sites fine and am writing this from the mac I'm having these problems on...
posted by Tacodog at 11:32 PM on October 6, 2007

ping antara.co.id
PING antara.co.id (202.134.4.18): 56 data bytes
ping: sendto: No route to host

Well, it looks like your DNS is working (and my ping gives the same IP).

Did you reset to factory defaults when you reflashed your firmware? Their might be some setting that is messing things up. After reseting back to defaults, if that works then try changing each setting from its default to what you want, being sure to check the sites between each change.
posted by philomathoholic at 11:50 PM on October 6, 2007

Yep, sure did. And just as before, the wired xp box can see the antara.co.id links just fine. The mac, whether in wireless or wired mode, cannot get there yet it still can access other sites. I get the same result with firefox or safari. This is baffling.
posted by Tacodog at 11:57 PM on October 6, 2007

Holy cow, it was PeerGuardian blocking access. Even after I quit the application and even after I rebooted and never launched it.

There are two demons run at login, pploader and pplogger. I know there's something else running I'm missing because even when I quit those demons in the Activity Monitor I still can't get to those websites. But if I run PeerGaurdian, disable all filters then quit the app, I can finally access those websites.

Thanks for all the help and the recommendations for Tomato--it really is neat. I'll be researching PeerGuardian for mac to see why it leaves its demon running even if the app is quit. Strange.
posted by Tacodog at 11:00 AM on October 7, 2007