We run Nomad on OpenStack instances which have a default MTU of 1450 for VXLAN networks. We are trying to figure out if it’s possible to set the MTU of the bridge network Nomad uses for Consul Connect services. We tried making a custom bridge network with a specified MTU, but it looks like Consul Connect only works with the built-in default bridge network which doesn’t currently have a way to specify it.
According to the bridge CNI documentation, the MTU “Defaults to the value chosen by the kernel.” Is there some way to use some OS level network setting to get the default MTU to match our interface properly? Or is the only option to try to update Nomad to allow specifying a custom MTU value for the built-in bridge?