Cristian Livadaru's blog

... think again ...

IPCop Slow When Running Torrents?

IPCop Support :: IPCops support & net security

Finaly I found the solution to my problem

I found that with a large number of connections – especially with the transient connections Bit Torrent users behind the Green interface generate – the ARP table would fill very quickly and prevent the establishment of new connections. This was evident primarily in messages from Squid when browsing that there was “No buffer space available”. However, this also prevented Bit Torrent from opening new connections and effectively decimated its performance too. Have a look at the Network Status page in IPCop and check the number of ARP entries listed. I think the default limit is ~4096 (someone want to correct me?) – if you find you are close to the limit append the following to /etc/sysctl.conf:

net.ipv4.neigh.default.gc_thresh1=4096 
net.ipv4.neigh.default.gc_thresh2=16384 
net.ipv4.neigh.default.gc_thresh3=32768