Bad modem/routers for P2P

I recently found a intersting list of modems/routers that do not survive well with P2P applications (let’s remember here that these applications can be very stressful for a network and its devices: hundreds or thousands of connections with a total traffic usually reaching the maximum limit of the network link). This is a list of incompatibilities collected for Azureus, but it also applies to uTorrent and probably most of the other P2P applications (including my own prefered BitComet).

Reason not yet verified

• Apple Airport Extreme (802.11g wireless with 128-bit WEP)

Due to too many connections

• SpeedStream 5660 in Router/NAPT configuration. There is no firmware newer than 2.(3).7. Switch to bridged mode and firewall your network to fix it. Otherwise, when it dies just power-cycle the router and continue on.

The following modems/routers have known problems with too many global connections, limiting them to 200 or less should fix the problems:

• D-Link 302G
• D-Link DI-624
• D-Link DSL-G664T
• Linksys BEFSR41V4/BESR41
• Linksys Wireless-B
• Netgear DG632
• Netgear DG834G
• Netgear MR814
• Netgear WGT524
• Netgear Rangemax 802.11n WPN824
• W-Linx MB401-S (and SMC Barricade 7004 BR, which is identical in construction)
• Westell 6100

Due to UPnP

• Most D-Link 5xx and 6xx (can also be caused by too many connections)
• D-Link DI-604
• Dynalink RTA1025W
• TP-LINK TL-R410
• ZyXEL Prestige 660H(W) (Firmware versions PE8+ will fix this)
• Some SpeedStreams

Due to Port Forwarding

• D-Link DI-514 (not port forwarding UDP protocol consistently)

Common fixes for routers/modems freezing/crashing/etc

• Updating the router firmware
• Turning off the UPnP (in the client and in the router) and doing manual port forwarding
• Restricting the number of global connections to 200 or less (may need to go below 100, depending on the router)
• Turning off DHT
• Lowering net.max_halfopen and bt.connect_speed
• Putting the modem/router into bridge or gateway mode (doesn’t apply to modems that aren’t routers)
• Getting a new router/modem

Sources: µTorrent FAQ and Bad routers – AzureusWiki.