Linux : ip_conntrack: table full, dropping packet

By | February 19, 2013

Having slow network performances, packet loss and noticed this message in the logs or dmesg output under heavy load on your Linux box?

ip_conntrack: table full, dropping packet

This is because you reach the limit set for connection tracking.

To display the current usage, use the following command :

In such case, you might want to increase the value (default is 65536) :

This will make the value increased instantaneously on your system. It won’t survive to the next reboot, so you need to add this new setting to sysctl :

CAUTION : Do not play blindly applying this setting. Each connection take around 350 Bytes of memory on your system. Make sure to have enough available memory before doing it.