Configuring OpenStack to use jumbo frames (MTU 9000)

Controller nodes

Disable puppet :

# systemctl stop puppet
# systemctl disable puppet

Place a given controller into standby mode :

# pcs cluster standby $(hostname)

Update the MTU for all physical NICs being used by either provider or tenant networks :

# echo MTU=9000 >> /etc/sysconfig/network-scripts/ifcfg-eth0

Update the various Neutron related configuration files :

Note that if tenant networks are being used then we need to allow for the overhead of VXLAN and GRE.

# echo “dhcp-option-force=26,8900” > /etc/neutron/dnsmasq-neutron.conf
# openstack-config –set /etc/neutron/dhcp_agent.ini DEFAULT dnsmasq_config_file /etc/neutron/dnsmasq-neutron.conf
# openstack-config –set /etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini agent veth_mtu 8900
# openstack-config –set /etc/neutron/l3_agent.ini DEFAULT network_device_mtu 9000
# openstack-config –set /etc/nova/nova.conf DEFAULT network_device_mtu 9000

Reboot to ensure everything persists.

# reboot

Unstandby the node and repeat on the remaining controllers :

# pcs cluster unstandby $(hostname)

Compute nodes

Disable puppet :

# systemctl stop puppet
# systemctl disable puppet

Update the MTU for all physical NICs being used by either provider or tenant networks :

# echo MTU=9000 >> /etc/sysconfig/network-scripts/ifcfg-eth0

Update the OVS plugin configuration file :

# openstack-config –set /etc/neutron/plugins/openvswitch/ovs_neutron_plugin.ini agent veth_mtu 8900
# openstack-config –set /etc/nova/nova.conf DEFAULT network_device_mtu 9000

Reboot to ensure everything persists.

# reboot

Source: https://access.redhat.com/solutions/1417133