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I am having some trouble with (I suspect) my wireless router. It's connected to the internet with a regular lan cable and has a static, public IP address. Our two home PCs connect to the router with regular lan cables, plus there's a laptop which connects over Wi-Fi.

diagram:
    Internet
       |
       | <- isp-supplied cat5 ethernet cable
       |
      D-Link D300 ...wifi... laptop
     /           \
    / <- cable -> \
  PC1             PC2

The PCs and laptop are behind NAT and share the router's public IP. The router is a D-Link D300. PC1 is used for online gaming and I'm experiencing frequent "connection dropped" errors when playing Battlefield 3, StarCraft 2 and the Diablo 3 beta; but not with TeamFortress 2 or the Tribes Ascend beta. The issue goes away when I remove the router and connect PC1 directly to the ISP's cable. I have also tried disconnecting PC2 and the laptop, leaving PC1 as the only machine connected to the router - doesn't How can I diagnose what precisely the issue is?

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migrated from serverfault.com Apr 6 '12 at 15:49

This question came from our site for professional system and network administrators.

    
Unless you run a business and that business's purpose is playing SC2 and Battlefield 3 and you're the system administrator for said business... this probably isn't an appropriate question for Serverfault. –  Safado Apr 6 '12 at 15:47
    
Fair enough. Thanks for moving it, then. –  Moshev Apr 6 '12 at 15:51
    
Might check to see if you can update the firmware on the router? Are you running any other internet services while you are playing (bittorrent, streaming, etc.)? –  jmreicha Apr 6 '12 at 16:33
    
Firmware is already at latest version and I only have skype running. –  Moshev Apr 6 '12 at 17:59

2 Answers 2

up vote 2 down vote accepted

Well, if you connect PC1 directly to the ISP it works. If you put the router in between it does not work. You have done the correct error searching process and found that the router is the problem.

Why is it the problem? It sounds like it is choking on your packets. The internet speed is probably higher than what the router can manage. The D-Link D300 is in the low-budget spectrum of routers, and this is not an uncommon problem.

The games that work perhaps simply do not generate as much data, or have more fault tolerance regarding latency before skipping.

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I can't +1 this hard enough. I think it's very obvious that, regardless of the exact cause, it's something on the router, and almost certainly that it simply can't handle the traffic for some reason. –  Shinrai Apr 6 '12 at 16:52
    
Sounds entirely plausible. Can you then suggest a replacement or at least what to look for in one? –  Moshev Apr 6 '12 at 17:27
    
This site is explicitly not for buying recommendations, but if I give some tips in these comments, no one will ever know [diabolical laugh]. I use a Netgear WNR-3500L, and I have recommended that for a couple of other persons over the years. In my country it goes for currency translated $75. I have heard good things about D-Link DIR-655. As a rule of thumb, routers give you what you pay for. Look at smallnetbuilder.com for great comparisons. –  Daniel Andersson Apr 6 '12 at 18:02
    
I replaced the router and now everything works fine. Thanks for the help! –  Moshev Apr 7 '12 at 13:26

Classicaly, cheap consumer routers' NAT tables don't play well with lots of connections (e.g. P2P) from lots of devices behind those routers... Once the table is full, that's it. Some devices allow to set a lower time-to-live for the entries in the table. Usually just buying a more powerful device i.e. more memory = bigger tables will do the trick. In Bittorrent for example you can also try to lower the total number of connections made.

In essence, if you need to keep the ISP's device, you put it into bridging mode and connect another more powerful router that performs the NAT behind it. Onto that router, you then connect the devices.

Sometimes, you can also plug several devices directly into the ISP's router, even if it is in bridging mode. Then you get several public IPs for each device. However the maximum allowed number in that case is usually very low, if it is possible at all.

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