@@ -23,7 +23,9 @@ Physical Network Setup

 In most cases where DevStack is being deployed with a single

 interface, there is a hardware router that is being used for external

 connectivity and DHCP. The developer machine is connected to this

-network and is on a shared subnet with other machines.

+network and is on a shared subnet with other machines.  The

+`local.conf` exhibited here assumes that 1500 is a reasonable MTU to

+use on that network.

 .. nwdiag::

@@ -434,6 +436,16 @@ bridge, to forward traffic sent by guest VMs.

 Miscellaneous Tips

 ==================

+Non-Standard MTU on the Physical Network

+----------------------------------------

+

+DevStack defaults to assume that the MTU on the physical network

+is 1500.  A different MTU can be specified by adding the following to

+the `localrc` part of `local.conf` on each machine.

+

+::

+    Q_ML2_PLUGIN_PATH_MTU=1500

+

 Disabling Next Generation Firewall Tools

 ----------------------------------------