Create the interface to enable proxy ARP

Before you create the TCP/IP interfaces, you need to decide how you want to connect your virtual Ethernet to a physical LAN. To allow your logical partitions to communicate with systems on an external LAN, you need to enable the TCP/IP traffic to travel between the virtual Ethernet and the external LAN. There are three methods for connecting the virtual and external networks: Proxy ARP, network address translation (NAT), and TCP/IP routing. This scenario uses the Proxy ARP method. For more information about all three methods of connecting this network traffic, see TCP/IP techniques connecting virtual Ethernet to external LANs.

To create the TCP/IP interface to enable proxy ARP, complete these steps:

1. Obtain a contiguous block of IP addresses that are routable by your network.

   Because you have a total of four logical partitions in this virtual Ethernet, you need a block of eight addresses. The fourth segment of the first IP address in the block must be divisible by eight. The first and last IP addresses of this block are the subnet and broadcast IP addresses and are unusable. The second address can be used for a virtual TCP/IP interface on logical partition A, and the third, fourth, and fifth addresses can be used for the TCP/IP connections on each of the other logical partitions. For this scenario, the IP address block is 10.1.1.72 through 10.1.1.79 with a subnet mask of 255.255.255.248.

   You also need a single IP address for your external TCP/IP address. This IP address should not belong to your block of contiguous addresses, but it must be within the same original subnet mask of 255.255.255.0.

2. Create an i5/OS™ TCP/IP interface for logical partition A. This interface is known as the external, proxy ARP IP interface.
   To create the interface, follow these steps:

   1. At the command line on partition A, type CFGTCP, and press Enter to see the Configure TCP/IP display.
   2. Select option 1 (Work with TCP/IP Interfaces), and press Enter.
   3. Select option 1 (Add), and press Enter to see the Add TCP/IP Interface (ADDTCPIFC) display.
   4. For the Internet address prompt, type 10.1.1.15.
   5. For the Line description prompt, type the name of your line description, such as ETHLINE.
   6. For the Subnet mask prompt, type 255.255.255.0.
3. Start the interface. On the Work with TCP/IP Interfaces display, select option 9 (Start) by the interface you want to start.