ZyXEL Communications wireless n gigbit router zyxel manual Triangle Routes and IP Alias, 181

Chapter 13 Firewall

You can have the NBG-460N permit the use of asymmetrical route topology on the network (not reset the connection).

Allowing asymmetrical routes may let traffic from the WAN go directly to the LAN without passing through the NBG-460N. A better solution is to use IP alias to put the NBG-460N and the backup gateway on separate subnets.

13.3.3 Triangle Routes and IP Alias

You can use IP alias instead of allowing triangle routes. IP Alias allow you to partition your network into logical sections over the same interface.

By putting your LAN and Gateway A in different subnets, all returning network traffic must pass through the NBG-460N to your LAN. The following steps describe such a scenario.

1A computer on the LAN initiates a connection by sending a SYN packet to a receiving server on the WAN.

2The NBG-460N reroutes the packet to Gateway A, which is in Subnet 2.

3The reply from the WAN goes to the NBG-460N.

4The NBG-460N then sends it to the computer on the LAN in Subnet 1.

Figure 122 Using IP Alias to Solve the Triangle Route Problem

NBG-460N User’s Guide

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