L3 IPV6 MTU

Neutron provides multiple ways to specify MTU for networks.

You can provide a global value in neutron.conf using global_physnet_mtu. It applies to all networks.

/etc/neutron/neutron.conf
[DEFAULT] 
global_physnet_mtu = <mtu_value>

You can provide a specific value when creating the network using the --mtu option. This value takes higher precedence and overrides the global value.

openstack network create –mtu <mtu_value> GREEN_NETWORK

The MTU value for each network is captured by Extreme‘s plugins and passed to EFA. EFA then enforces the value on the EPG as part of its ipv6-nd-mtu option. This value is per ctag and is enforced on the VE interface corresponding to the ctag. EFA configures the MTU value on the specific VE interface on the switch.

The value is applied to the SLX switch when router-interface is associated with the network in Neutron – either when the router is added to a subnet that is associated with the network or when a port on the network is added to a router.

Example

The following is a sample SLX configuration.

Rack1-Device1# show running-config interface Ve 11 
vrf forwarding ten1vrf1 
ip anycast-address 10.10.11.1/24 
ipv6 anycast-address fd00:10:0:57::1000/64 
ipv6 nd mtu 2100 
no shutdown !