Need help with server running behind router and DSL modem

seanstephenson · 11-03-2006, 12:38 AM

Hi everyone, I am having trouble getting my computer to accept incoming connections. My computer is connected to a Netgear Wireless Router, model WGR614v6. The router is connected to an Actiontec GT701 DSL modem. I have port forwarding set up on both of them on the appropriate ports, in this case 3389 for remote desktop, 80 for HTTP server, 2401 for CVS server, and others. The server software is running perfectly on my computer. I can connect to localhost from my computer, and to my computer's IP from within the LAN. However, when I try to connect from my computer at work I have problems.

I have never seen this behavior before. The connection is accepted, but then very little or no traffic gets through the connection. I know that at least some traffic gets through sometimes because if I run the cvs command from my work computer it connects and after about 3 minutes will have got the first three files, which it couldn't have done if my port forwarding was wrong.

Another strange thing is that if I connect my home computer directly into the DSL modem skipping the router the server works fine from remote locations. Could it be an interaction between the router and the DSL modem?

Can anyone help me understand what is wrong here?

seanstephenson · 11-03-2006, 01:38 AM

Ok, this just keeps getting stranger. From remote computers, I can get files through my HTTP server if the files are less than about 1000 bytes. Otherwise, the browser just hangs while loading. This is very reproducible. For files less than 1000 bytes or so, the server responds quickly and everything works fine. For files larger than this, the server accepts the connection but the browser times out while waiting.

Could it have something to do with the first packet getting through but no others? I have no idea why that would happen but it is just a guess.

johnwill · 11-03-2006, 06:42 AM

Try putting the machine in the DMZ of the router.

seanstephenson · 11-03-2006, 07:25 AM

John,
Thanks for your reply. I've put the machine in the DMZ of the router, and the same thing happens as when I just had the port forwarding set up. I can get files of about 1000 bytes or less remotely but any more than that fails. Would it be a good idea to try putting the router in the DMZ of the DSL modem? I have a software firewall so I wouldn't be wide open.

seanstephenson · 11-07-2006, 11:04 PM

Well, I figured it out. If anyone is having the same problem here is what worked for me. It turns out that my Internet connection is a PPPoE connection. My router had the MTU set to 1500, but for PPPoE it has to be set to 1492 (look in the WAN setup for your router). That's why anything over 1492 bytes was failing (which for web pages was about 1000 bytes plus HTTP headers), while everything under that amount worked fine.

I found this solution on a couple different knowledge bases and after changing the MTU from 1500 to 1492, everything started working fine for me. Other sites mentioned that if you have different kinds of Internet connections you may have to set it as low as 1400. The general idea is to have it as large as possible where everything works. Good luck.

johnwill · 11-12-2006, 02:45 PM

I'm surprised that this didn't get set automatically when you connected the router to a PPPoE modem.

In any case, thanks for the feedback.

11-03-2006, 12:38 AM	#1 (permalink)
seanstephenson Registered User Join Date: Nov 2006 Posts: 4 OS: Windows XP	Need help with server running behind router and DSL modem Hi everyone, I am having trouble getting my computer to accept incoming connections. My computer is connected to a Netgear Wireless Router, model WGR614v6. The router is connected to an Actiontec GT701 DSL modem. I have port forwarding set up on both of them on the appropriate ports, in this case 3389 for remote desktop, 80 for HTTP server, 2401 for CVS server, and others. The server software is running perfectly on my computer. I can connect to localhost from my computer, and to my computer's IP from within the LAN. However, when I try to connect from my computer at work I have problems. I have never seen this behavior before. The connection is accepted, but then very little or no traffic gets through the connection. I know that at least some traffic gets through sometimes because if I run the cvs command from my work computer it connects and after about 3 minutes will have got the first three files, which it couldn't have done if my port forwarding was wrong. Another strange thing is that if I connect my home computer directly into the DSL modem skipping the router the server works fine from remote locations. Could it be an interaction between the router and the DSL modem? Can anyone help me understand what is wrong here?

11-03-2006, 01:38 AM	#2 (permalink)
seanstephenson Registered User Join Date: Nov 2006 Posts: 4 OS: Windows XP	Even stranger Ok, this just keeps getting stranger. From remote computers, I can get files through my HTTP server if the files are less than about 1000 bytes. Otherwise, the browser just hangs while loading. This is very reproducible. For files less than 1000 bytes or so, the server responds quickly and everything works fine. For files larger than this, the server accepts the connection but the browser times out while waiting. Could it have something to do with the first packet getting through but no others? I have no idea why that would happen but it is just a guess.

11-03-2006, 06:42 AM	#3 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 30,227 OS: XP-Pro, Vista, Linux Blog Entries: 1	Try putting the machine in the DMZ of the router. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

11-07-2006, 11:04 PM	#5 (permalink)
seanstephenson Registered User Join Date: Nov 2006 Posts: 4 OS: Windows XP	Had to change my MTU setting Well, I figured it out. If anyone is having the same problem here is what worked for me. It turns out that my Internet connection is a PPPoE connection. My router had the MTU set to 1500, but for PPPoE it has to be set to 1492 (look in the WAN setup for your router). That's why anything over 1492 bytes was failing (which for web pages was about 1000 bytes plus HTTP headers), while everything under that amount worked fine. I found this solution on a couple different knowledge bases and after changing the MTU from 1500 to 1492, everything started working fine for me. Other sites mentioned that if you have different kinds of Internet connections you may have to set it as low as 1400. The general idea is to have it as large as possible where everything works. Good luck.

11-12-2006, 02:45 PM	#6 (permalink)
johnwill Manager, Networking Forums Join Date: Sep 2002 Location: S.E. Pennsylvania, US Posts: 30,227 OS: XP-Pro, Vista, Linux Blog Entries: 1	I'm surprised that this didn't get set automatically when you connected the router to a PPPoE modem. In any case, thanks for the feedback. __________________ If TSF has helped you, Tell us about it! or Donate to help keep the site up! Microsoft MVP - Windows Desktop Experience

11-03-2006, 07:25 AM	#4 (permalink)
seanstephenson Registered User Join Date: Nov 2006 Posts: 4 OS: Windows XP	John, Thanks for your reply. I've put the machine in the DMZ of the router, and the same thing happens as when I just had the port forwarding set up. I can get files of about 1000 bytes or less remotely but any more than that fails. Would it be a good idea to try putting the router in the DMZ of the DSL modem? I have a software firewall so I wouldn't be wide open.