Vehicle Mounted Modem (VMM) Deployment Considerations

Before defining a VMM configuration, refer to the following deployment guidelines to ensure the configuration is optimally effective:

• Disable layer 2 stateful packet inspection from the firewall policy.
• Set the RTS threshold value to 1 on all mesh devices. The default value is 65,536.
• Disable Dynamic Chain Selection (radio setting). The default value is enabled. This setting is disabled from the Command Line Interface (CLI) using the dynamic-chainselection command, or, in the UI (refer to Overriding Radio Configurations).
• Disable A-MPDU Aggregation if the intended vehicular speed is greater than 30 mph. For more information, see Overriding Radio Configurations.
• Set a misconfiguration recovery time for the non-root AP profile. This configuration should delay the rejection of the newest configuration push from the controller, potentially causing adoption loss.

  The additional delay is to support cases when the new configuration from the controller causes the root AP to move from current channel to other channels, resulting in a mesh link going down, and in turn non-root APs losing adoption. This delay accommodates the time needed for the non-root AP to scan all channels and finding the best root node. The non-root AP can begin operating on the new channel, and establish the mesh link re-adopt to the controller. (For countries using DFS, the scan time is also factored in for the configured value). If the AP fails to find a suitable root node within this time, this new config is a misconfigured and the device would reject the latest config.