# Running in IPv4/IPv6 dual stack mode

CG boards implement an IPv4/IPv6 dual stack that allows applications to configure the board in any of the following modes:

IP stack mode | Description
IPv4 only | Default mode of operation for CG boards. You configure specific IPv4 addresses and routing information with the IPC.AddRoute keywords.
IPv6 only | Enable by setting the IPv6.Link[x].Enable keyword to YES for a particular Ethernet interface. The IPv4 stack remains passive if no IPv4 addresses are configured with IPC.AddRoute keywords.
IPv4/IPv6 dual stack | Add IPv4 addresses with IPC.AddRoute keywords, and enable IPv6 capability on a particular interface with the IPv6.Link[x].Enable keyword.

You can configure the board Ethernet links in any of the following ways:

- Configure the Ethernet link separately for IPv4 and IPv6 support.

- Configure separate protocols for separate Ethernet links.

- Configure both protocols for either one or both links.

The only interaction between the IPv4 and IPv6 protocol stacks occurs when a CG board is configured in redundant Ethernet mode.

The CG board IPv6 stack does not support redundant Ethernet configurations in the manner supported by the IPv4 stack. To implement IPv4 redundant Ethernet capabilities while using IPv6, you must enable the IPv6 stack only on the first Ethernet interface. Enabling IPv6 on the second Ethernet link places the Ethernet interfaces in dual Ethernet mode rather than redundant Ethernet mode.