# Configuring the board in dual subnet mode

To direct different types or classes of IP traffic to separate IP networks, you can associate each CG 6565C board Ethernet interface with a separate IP address. When you configure the secondary Ethernet connection with an IPv4 address or enable IPv6 on the secondary Ethernet connection, the board operates in dual subnet mode rather than redundant Ethernet mode.

It is possible to configure both Ethernet connections into the same IPv4 subnet, but this is not recommended. When configured in this manner, the CG 6565C board receives packets for both addresses. Based on standard IPv4 routing practice, outbound packets take the first route that matches. Therefore, the CG board sends all outbound IPv4 packets to the Ethernet connection associated with the first IPv4 address in the routing table.

### Example

The following example shows how to configure a CG 6565C board in dual subnet mode. Each Ethernet interface is configured for a separate Class C subnet, and each specifies a separate router. However, the second router is configured so that only IPv4 addresses in the Class A subnet of 10.x.y.z are forwarded to the second router. All other external IPv4 addresses are forwarded to the first router.

# Specify IPv4 address
IPC.AddRoute[0].DestinationAddress = 198.62.139.32
IPC.AddRoute[0].Mask = 255.255.255.0
IPC.AddRoute[0].Interface = 1
# Specify route
IPC.AddRoute[1].DestinationAddress = 0.0.0.0
IPC.AddRoute[1].Mask = 0.0.0.0
IPC.AddRoute[1].GatewayAddress = 198.62.139.1
# Specify IPv4 address
IPC.AddRoute[2].DestinationAddress = 198.62.140.75
IPC.AddRoute[2].Mask = 255.255.255.0
IPC.AddRoute[2].Interface = 2
# Specify route
IPC.AddRoute[3].DestinationAddress = 10.0.0.0
IPC.AddRoute[3].Mask = 255.0.0.0
IPC.AddRoute[3].GatewayAddress = 198.62.140.1