Troubleshooting the Grid Network MTU mismatch alert

The Grid Network MTU mismatch alert is triggered when the maximum transmission unit (MTU) setting for the Grid Network interface (eth0) differs significantly across nodes in the grid.

About this task

The differences in MTU settings could indicate that some, but not all, eth0 networks are configured for jumbo frames. An MTU size mismatch of greater than 1000 might cause network performance problems.

Procedure

  1. List the MTU settings for eth0 on all nodes.
    • Use the query provided in the Grid Manager.
    • Navigate to <primary Admin Node IP address>/metrics/graph and enter the following query: node_network_mtu_bytes{interface='eth0'}
  2. Modify the MTU settings as necessary to ensure they are the same for the Grid Network interface (eth0) on all nodes.
    • For appliance nodes, see the installation and maintenance instructions for your appliance.
    • For Linux- and VMware-based nodes, use the following command: /usr/sbin/change-mtu.py [-h] [-n node] mtu network [network...]
      Example: change-mtu.py -n node 1500 grid admin
      Note: On Linux-based nodes, if the desired MTU value for the network in the container exceeds the value already configured on the host interface, you must first configure the host interface to have the desired MTU value, and then use the change-mtu.py script to change the MTU value of the network in the container.

      Use the following arguments for modifying the MTU on Linux- or VMware-based nodes.

      Positional arguments Description
      mtu The MTU to set. Must be in the range 1280 to 9216.
      network The networks to apply the MTU to. Include one or more of the following network types:
      • grid
      • admin
      • client
      Optional arguments Description
      -h, – help Show the help message and exit.
      -n node, --node node The node. The default is the local node.