Using IP Alias

- What is IP Alias ?

In a typical environment, a LAN router is required to connect two local networks. The ZyAIR is enhanced to connect three local networks to the ISP or a remote node, we call this function as 'IP Alias'. In this case, an internal router is not required. For example, the network manager can divide the local network into three networks and connect them to the Internet using ZyAIR's single user account. See the figure below.

The ZyAIR supports three virtual LAN interfaces via its single physical Ethernet interface. The first network can be configured in menu 3.2 as usual. The second and third networks that we call 'IP Alias 1' and 'IP Alias 2' can be configured in menu 3.2.1-IP Alias Setup.

There are three internal virtual LAN interfaces for the ZyAIR to route the packets from/to the three networks correctly. They are enif0 for the major network, enif0:0 for the IP alias 1 and enif0:1 for the IP alias 2. Therefore, three routes are created in the ZyAIR as shown below when the three networks are configured. If the ZyAIR's DHCP is also enabled, the IP pool for the clients can be any of the three networks.

`Copyright (c) 1994 - 2004 ZyXEL Communications Corp.` `ras> ip ro st` `Dest FF Len Interface Gateway Metric stat Timer Use` `192.168.3.0 00 24 enif0:1 192.168.3.1 1 041b 0 0` `192.168.2.0 00 24 enif0:0 192.168.2.1 1 041b 0 0` `192.168.1.0 00 24 enif0 192.168.1.1 1 041b 0 0` `ras>`

Two new protocol filter interfaces in menu 3.2.1 allow you to accept or deny LAN packets from/to the IP alias 1 and IP alias 2 go through the ZyAIR. The filter set in menu 3.1 is used for main network configured in menu 3.2.

- IP Alias Setup

1. Edit the first network in menu 3.2 by configuring the ZyAIR's first LAN IP address.

`Menu 3.2 - TCP/IP and DHCP Ethernet Setup DHCP= Server TCP/IP Setup: Client IP Pool: Starting Address= 192.168.1.33 IP Address= 192.168.1.1 Size of Client IP Pool= 32 IP Subnet Mask= 255.255.255.0 First DNS Server= From ISP RIP Direction= Both IP Address= N/A Version= RIP-1 Second DNS Server= From ISP Multicast= None IP Address= N/A Edit IP Alias= Yes Third DNS Server= From ISP IP Address= N/A DHCP Server Address= N/A Press ENTER to Confirm or ESC to Cancel:`

Key Settings:

DHCP Setup | If the ZyAIR's DHCP server is enabled, the IP pool for the clients can be any of the three networks.
TCP/IP Setup | Enter the first LAN IP address for the ZyAIR. This will create the first route in the enif0 interface.
Edit IP Alias | Toggle to 'Yes' to enter menu 3.2.1 for setting up the second and third networks.

2. Edit the second and third networks in menu 3.2.1 by configuring the ZyAIR's second and third LAN IP addresses.

`Menu 3.2.1 - IP Alias Setup` `IP Alias 1= Yes` `IP Address= 192.168.2.1` `IP Subnet Mask= 255.255.255.0` `RIP Direction= None` `Version= RIP-1` `Incoming protocol filters=` `Outgoing protocol filters=` `IP Alias 2= Yes` `IP Address= 192.168.3.1` `IP Subnet Mask= 255.255.255.0` `RIP Direction= None` `Version= RIP-1` `Incoming protocol filters=` `Outgoing protocol filters=` `Enter here to CONFIRM or ESC to CANCEL:`

Key Settings:

IP Alias 1 | Toggle to 'Yes' and enter the second LAN IP address for the ZyAIR. This will create the second route in the enif0:0 interface.
IP Alias 2 | Toggle to 'Yes' and enter the third LAN IP address for the ZyAIR. This will create the third route in the enif0:1 interface.

All contents copyright © 2004 ZyXEL Communications Corporation.