L3 IP MTU
Neutron provides multiple ways to specify the maximum transmission unit (MTU) for networks.
You can provide a global value in the
neutron.conf file using the global_physnet_mtu value. This value
applies to all networks. For
example:/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. For
example:openstack network create –-mtu <mtu-value> GREEN_NETWORK
The MTU value for each network is captured by Extreme plug-ins and passed to EFA. EFA then
enforces the value on the endpoint group as part of its ipv6-nd-mtu and
ip-mtu options. This value is per Ctag and is enforced on the VE interface
corresponding to the Ctag. EFA configures the ipv6-nd-mtu and
ip-mtu values on the specific VE interface on the device.
The value is applied to the SLX device when the 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.(device)# show running-config interface Ve 3 interface Ve 3 vrf forwarding 274e9461081849f8867b77a112f6c510 ip anycast-address 61.1.1.1/24 ip mtu 9000 ipv6 anycast-address fd00:61:0:57::1/64 ipv6 nd managed-config-flag ipv6 nd other-config-flag ipv6 nd mtu 9000 ipv6 nd prefix fd00:61:0:57::/64 2592000 604800 no-autoconfig no shutdown
Note
SLX supports IP MTU values in the range from 1280 through 9194 bytes. Creation of the router-interface fails if you try to configure an MTU value outside of this range.