Doug’s Blog

Handily dispensing information to .00000001% of the world’s population

Archive for February, 2016

Increasing Network Connections in Centos7

Wednesday, February 24th, 2016

I had a client who was losing network connectivity intermittently recently and it turns out they needed to increase the high limit for network connections. Centos7 has some variable name changes from previous versions so here are some helpful tips on how to increase the limits.

In older Centos you might have seen these error messages:

ip_conntrack version 2.4 (8192 buckets, 65536 max) – 304 bytes per conntrack

In newer verions, something like:

localhost kernel: nf_conntrack: table full, dropping packet

The below is for Centos versions that have renamed the ip_conntrack to nf_conntrack.

To get a list of network parameters:

sysctl -a | grep netfilter

This shows current value for the key parameter:

/sbin/sysctl net.netfilter.nf_conntrack_max

This shows your system current load:

/sbin/sysctl net.netfilter.nf_conntrack_count

So now to update the value in the kernel to triple the limit, of course make sure your RAM has room with what you choose:

/sbin/sysctl -w net.netfilter.nf_conntrack_max = 196608

To make it permanent after reboot, please add these values to the /etc/sysctl.conf

net.ipv4.netfilter.ip_conntrack_max = 196608

Hope this helps!