# Configuring the board in redundant Ethernet mode

By default, the Ethernet subsystem on the CG 6565E board initializes in redundant Ethernet mode. In this mode, Ethernet 1 provides the primary Ethernet connection and Ethernet 2 operates in a standby mode.

All IPv4 configuration and routing information applies to both the primary and secondary Ethernet connection. If the primary connection loses link integrity, the secondary connection takes over. Once link integrity returns to the primary connection, all Ethernet traffic converts back to the primary Ethernet connection.

While in standby mode, the secondary Ethernet connection establishes link integrity, but remains passive. It does not send or receive packets to or from the IP network. When the primary connection loses link integrity, the secondary connection enables its transmitter and receiver and takes over for the primary connection. The fallback process is automatic, occurring in less than 1 ms, and is transparent to both the network and the application.

If you explicitly configure the secondary Ethernet connection with any IP addressing information or enable IPv6 on the secondary Ethernet connection, you disable the board’s redundant Ethernet capability.

### Example

The following example shows how to configure a CG 6565E board in redundant Ethernet mode. This example shows a CG 6565E board on a Class C subnet (198.62.139.x) with a single router providing access to the external IP network.

When you specify 0.0.0.0 as the router destination address and subnet mask, all IP addresses not on the local subnet (198.62.139.x) are forwarded to the router 198.62.139.1 (typically referred to as the default route).

IPC.AddRoute[0].DestinationAddress = 198.62.139.32
IPC.AddRoute[0].Mask = 255.255.255.0
IPC.AddRoute[0].Interface = 1
IPC.AddRoute[1].DestinationAddress = 0.0.0.0
IPC.AddRoute[1].Mask = 0.0.0.0

IPv6 connections support a type of path redundancy not supported on IPv4 connections. For information about setting up path redundancy in configurations that support IPv6 connections, refer to IPv6 path redundancy.