HOWTO: “ip_conntrack: table full, dropping packet”

I used to manage a server based on linux and once I had this strange message:

$ ip_conntrack: table full, dropping packet

One of the effects of this message is that you aren’t able to make and receive new connections.
To solve that is enough increase ip_conntrack_max value. As first step check the current value typing:

$ cat /proc/sys/net/ipv4/ip_conntrack_max
65536

Now, increase this value typing:

$ echo 131072 > /proc/sys/net/ipv4/ip_conntrack_max

Generally the right value of ip_conntrack_max is set to the total MB of RAM multiplied by 16. If you have 8GB RAM (8192 MB), the value should be 131072.