By default, Ethernet frames for networks created on each Chameleon site default to 1500 byte MTU (maximum transmission unit). However, all TOR switches on Chameleon are configured to allow for payloads of up to 9000 bytes. If you would like to experiment with jumbo frames on your private networks or over Layer 2 connections then please follow the steps below to implement.
You will not be able to send jumbo frames out over the public internet, as many commercial networks do not support jumbo frames. You also will not be able to send jumbo frames across two separate tenant networks via an OpenStack router. However, traffic between your nodes or over a stitched layer2 network like ExoGENI can all utilize jumbo frames.
Do not set your MTU value greater than 9000. MTUs greater than 9000 bytes are not supported on Chameleon.
Enabling Jumbo Frames When Creating a Network
Enabling jumbo frames on a new network will ensure that the first Ethernet interface on all newly created baremetal instances will have its MTU set to the value specified.
openstack network create --provider-network-type vlan --mtu 9000 \
--provider-physical-network physnet1 <network_name>
You can verify the MTU is correct on your instance with the command
ifconfig eno1. The first Ethernet interface is typically
most Chameleon base images.
Enabling Jumbo Frames on Existing Network
You can also modify the MTU of an existing network using the command below. Please note that this will only effect newly created baremetal instances.
openstack network set <network_name> --mtu 9000
Enabling Jumbo Frames on Existing Instances
Setting the MTU on your Chameleon network only affects instances on boot to set the first Ethernet interface. If you already have a live baremetal instance then you can simply use the command below on the instance to set MTU manually.
sudo ip link set dev eno1 mtu 9000