Configuring Multiple Logical Interfaces

Novell TCP/IP allows you to bind more than one IP network to a LAN board. The networks can operate as separate logical interfaces. The ability to configure multiple logical interfaces simplifies the task of managing a growing network in the following ways:

• You can merge network when a there is a router failure.

  For a description, see Merging Two Networks When the Connecting Router Fails.

• You can move hosts from one IP network to another without losing connectivity.

  For a description, see Reassigning IP Addresses.

• You can add new nodes to a nearly full subnet.

  For a description, see Adding New Nodes to a Full Subnet.

To attach more than one IP network to a LAN board, bind IP to the board as many times as necessary; then supply a different IP address for each network.

Configuring multiple logical interfaces is different from multihoming, which enables you to bind multiple addresses belonging to the same IP network to the same interface or different interfaces. To configure multihoming, see Configuring a Secondary IP Address.

Merging Two Networks When the Connecting Router Fails

Suppose a router that connects IP networks 130.81.0.0 and 167.10.0.0 fails. For simplicity, assume that the physical medium is Ethernet. If the router cannot be repaired quickly, you can temporarily fix the problem by completing the following steps:

1. Join the two networks into a single network segment using a barrel connector, a repeater, or other appropriate means.

2. Find a system operating Novell TCP/IP connected to the joined network.

3. Load INETCFG and select Protocols > TCP/IP.

4. Set IP Packet Forwarding to Enabled ("Router").

5. Press Esc until you are prompted to save your changes, and then select Yes.

6. Press Esc to return to the Internetworking Configuration menu.

7. Select Bindings and then bind IP to the joined network twice.

   1. Select an existing binding to an interface connected to the joined network.

   2. Set Local IP Address to an available host address on the first network. In this example, enter an available host address on the 130.81.0.0 network.

   3. Press Esc and then save your change when prompted.

   4. Press Ins to create a new binding and select the same interface connected to the joined network.

   5. Set Local IP Address to an available host address on the second network. In this example, enter an available host address on the 167.10.0.0 network.

8. Press Esc until you are prompted to save your changes, and then select Yes.

9. Press Esc to return to the Internetworking Configuration menu.

10. If you want these changes to take effect immediately, select Reinitialize System > Yes.

Reassigning IP Addresses

Suppose you must change network number 89 to 130.57. If the system does not have multiple logical interfaces, you must change all IP addresses on network 89 at the same time or lose connectivity to any host that did not have its address changed.

With multiple logical interfaces, you can assign the new IP addresses gradually. Networks 89 and 130.57 can coexist on the same network segment until the transition is complete. The router interfaces, attached to both logical networks, forward packets for each network and route packets between the two.

Adding New Nodes to a Full Subnet

Suppose you want to add several new nodes to a subnet that has no more available IP addresses. Assume that the network has enough free connectors available to physically attach the nodes.

First, you assign a new subnet number to the cable so that both subnets share the cable. Then to add new nodes, you bind their IP address to the new logical subnet. The router whose interface is bound to both subnet addresses provides connectivity between the two subnets and to the rest of the internetwork.