Linksys WRT54G MTU problems
This has been a crazy week. On Wed, our employees from our remote office started complaining about not being able to send email attachments through our mail server. I tried nearly everything I could think of but kept getting postfix errors:
“timeout after DATA from xxxxx”
After beating my head against the wall, I ran across the Postfix FAQ which attributed the cause to a MTU issue. I tried a few workarounds they mentioned to no avail. No one else in the building was experiencing a problem with email and I could send email through our server from home just fine. After enumerating all my options and failing, I finally decided to upgrade to the latest linksys firmware (v3.1_4.00.7_US). I walked a coworker through the upgrade over the phone and the firmware was upgraded successfully. Yeah, at least it didn’t bork, I thought, but guess what? We get an IP through DHCP but the router isn’t sending any packets out the WAN interface…just great, freakin’ great. Luckily, after several reboots, and a changing to a static WAP IP the router started working again. We tested sending some large attachments and sure enough, everything works slick now.
I’m a fan of linksys but this kind of crap really pisses a guy off. I essentially wasted two days trying to solve this stupid thing and since I don’t have access to the firewall in the building and can’t drive 5 hours each way, I had to do it all over the phone. really, really, frustrating! Thankfully, we’re up and running now and I can go home happy today 
July 22nd, 2005 at 3:04 pm
I’m just kind of curious what changed. I mean why (with no firmware or postfix changes) did it STOP working in the first place? you KNOW there’s some slinky 3rd party firmware out for that thing though so maybe its time to get crazy with the cheeze whiz. (ah, probably not)
hey, and why do you not have access to the firewall? is that a design decision or an “oopsie?”
last note… I was in a rest-area bathroom once when someone tried to mess with my MTU. I was like “hey, buddy… you just timed out after DATA from xxxxx” and punched him in the ear. after that he didnt even consider touching my RWIN.
July 22nd, 2005 at 3:26 pm
I think what happened was someone changed an MTU setting on a router interface between our remote office and our mail server. This caused packet fragmentation that the Linksys firewall’s PAT-NAT didn’t like due to a firmware bug.
The building our office is in uses a shared cable connection for the entire building which is provided by the company which will be our main competitor in the area! Since it’s a shared connection, I can’t poke holes in the firewall to access the machines remotely. It’s really a PITA.
BTW, why are you hanging out at rest areas. You know they’re the YMCA of the 00’s right!? freak.
July 22nd, 2005 at 3:48 pm
Man I highly recomend the 1.0 version of alchemy firmware for that wrtg54g. I have been running it for a few months now and am very pleased. I have no knowledge of the MTU featuers of the bios, but it has been ROCK SOLID. I really like the ability to crank the signal strength on the wireless between 0-251mw. (The default from linksys is 28)
June 19th, 2009 at 3:40 pm
Long Distance Router…
Routers have come a long time in the last few years it’s amazing how much they’ve changed….