iptables

Booster · 05-18-2005, 08:26 AM

For the past few days I've been having trouble with my router - it's running 2.4.20/iptables, and what's happening is that certain websites will not load from any machine on the LAN.

If I try to go to http://www.mls.ca it finds the site, changes the name to "http://www.mls.ca/map.aspx" and hangs - almost.

If I do a "view source" on the page, I'll see that some of it has loaded, and if I check a minute later, there will likely be a bit more loaded, but even after many minutes it never gets past about 8k, and never will load.

Most sites work fine, I'd say it's <10% of sites that exhibit this issue. A couple others are:
http://www.autotrader.ca
http://www.jobbank.gc.ca

I connect through a T1, and I've even set up a new gateway machine running very simple routing rules:

Code:

iptables -A FORWARD -i eth1 -o eth0 -m state --state ESTABLISHED,RELATED -j ACCEPT

iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT

iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE

This second machine with simple rules exhibits the same problem.

I've played around with MTU a bit - no effect.

Any thoughts would be GREATLY appreciated - I have many users here, and they have been patient, but I'm quite eager to resolve this.

Thanks

[edit] I should add that the original router has been running for a very long time with many users without trouble. It was shut down about a week ago (just to move it), and the problem became apparent some days later (not sure, but the problem likely existed since last bootup)[/edit]

Darin · 05-18-2005, 09:50 AM

Quote:

Originally posted by Booster
This second machine with simple rules exhibits the same problem.

That leads me to belive that it's something upstream from you that is causing this problem, have you checked into that?

Booster · 05-18-2005, 11:42 AM

I believe you're right - I disconnected the entire network and just connected on PC to the outside, and it does the same thing....

I talked to my ISP... something tells me that this is going to be a lengthy battle.

Cheers

Booster · 01-31-2006, 10:52 PM

BTW: I did resolve this, but never really, to my satisfaction, figured it out. Anyway, here's what the "problem" was:
(hold on to your hat)
A fiber cable (multimode pair) had been zip-tied too tight. It was a fiber cable on my T1 line, and as soon as I bypassed it, shazzam, it worked. Go back, and it does it again.... I tried it a dozen times to be sure.
Once the dizzy spells stopped, I hooked it up through that fiber line again, and ran some tests....results:
- Same as before, some http traffic okay, some not. Consistantly the same sites.
- Tried lowering my MTU - it *improved*. Meaning some of the previous sites were okay, some not.
- Raised MTU back up, went back to same as before.
- Seemed as though some packets were too big to fit through the pinched cable.
- Dizzy spells started again. lol
- Dropped it, and tried to forget it. (That never worked... I still would like to understand)

Point of interest: I've had some cabling "pros" test the hell out of that cable, numerous times, and always got "it's fine" or better. (Those guys seem to not want me to see their meter. heh)

Anyway, just wanted some closure on the topic - I hate unanswered topics, and I left this one for a while.