Checking iptables filtering for bridge networking on Ubuntu (for Kubernetes setup)

If you’re installing and configuring a Kubernetes cluster on bare metal or in a VM yourself, one of the install steps using kubeadm says to check iptables filtering for bridge networking, but it doesn’t exactly say how to do this per distro.

The setting required is:

net.bridge.bridge-nf-call-iptables=1

There are specific steps in the kubadm docs above for RHEL/CentOS to add this setting. For Ubuntu it seems this is set by default, but you can confirm by:

sysctl net.bridge.bridge-nf-call-iptables

and the expected setting is 1:

net.bridge.bridge-nf-call-iptables = 1

It seems on Ubuntu 16.04 server this is set to 1 by default, but if it’s 0, you can edit this property in /etc/sysctl.conf

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