WireMode in SonicOS is a deployment option where the SonicWall can be deployed as a "bump in the wire". It provides a least intrusive way to deploy the appliance in a network, and is very well suited for deploying behind a pre-existing SPI firewall.
In versions of SonicOS prior to 22.214.171.124 (back to 126.96.36.199), WireMode supported only IPv4 networks. The feature has been expanded to now support IPv6 as well.
WireMode is a layer 2 protocol, so once an interface pair is configured in this way, they will automatically support both IPv4 and IPv6 with no need for additional configuration. If, for example, "Disable Stateful Inspection" is enabled, it will apply to both IP stacks.
Note: The SonicOS UI allows the administrator to configure WireMode only when the "View IP Version" option is set to IPv4. This option is located above the interfaces table on the Network > Interfaces page.