Novell Documentation: NetWare 6 - Balancing Traffic Loads over Equal-Cost Routes

Balancing Traffic Loads over Equal-Cost Routes

If a NLSP router has two or more network interfaces with routes to the same destination, it can distribute outbound traffic among those interfaces for an effective increase in throughput. This is called load balancing or load sharing .

NLSP uses an assigned path cost to select the best route by which to forward outbound IPX packets. The higher the throughput of the network medium, the lower the cost of the route.

Table 4 shows the throughput range and default cost of some typical network media.

Table 4. Throughput Range and Default Cost of Typical Network Media

Throughput Range	Default Cost	Typical Network Media
0-16 Kbps	61	9,600-baud line
48-64 Kbps	45	ISDN (U.S.)
64-128 Kbps	45	ISDN (Europe)
1-2 Mbps	27	Corvus Omninet (1 Mbps), T1 (1.5 Mbps)
2-4 Mbps	26	E1 (2 Mbps), ARCnet (2.5 Mbps)
4-8 Mbps	25	Token ring (4 Mbps), Corvus Omninet (4 Mbps)
10-16 Mbps	20	Ethernet (10 Mbps)
16-32 Mbps	19	Token ring (16 Mbps)
64-128 Mbps	14	FDDI (100 Mbps), CDDI (100 Mbps)

You can specify up to eight equal-cost routes to a single destination with the Maximum Number of Path Splits parameter. Two routes are equal in cost if the cost to the destination is the same for both routes. To equalize the costs of two interfaces, you set their Cost Override parameter to the same value. By default, Cost Override is set to 0 for all interfaces, which means that NLSP uses the default cost associated with the connected medium and throughput range listed in Table 4 .

If you configure equal-cost routes on two or more interfaces, make sure the associated media throughputs fall within---or near---the same range, as indicated in Table 4. For example, equal-cost routes between a 10-Mbps Ethernet link and a 16-Mbps token ring link are viable; equal-cost routes between a 4-Mbps token ring link and a 16-Mbps token ring link are not.

WARNING: Do not equalize the cost of routes whose throughputs differ greatly; this can interfere with the operation of IPX applications running over the network.

For more information about load balancing and path cost, refer to Understanding.

How to Balance Traffic Loads over Equal-Cost Routes

Before you begin, make sure of the following:

NLSP is enabled on all interfaces you plan to configure.

To enable NLSP globally or on one or more interfaces, refer to How to Configure NLSP.

The media over which you plan to configure equal-cost routes have the same or similar throughput ranges.
For a list of throughput ranges and associated media, refer to Table 4.

To configure load balancing over equal-cost routes, complete the following steps:

Load NIASCFG, then select the following parameter path:

Select Configure NIAS > Protocols and Routing > Protocols > IPX > Expert Configuration Options

Select the Maximum Number of Path Splits parameter, enter a value between 2 and 8, then press Enter .

Selecting a value of 2 or above automatically enables local load balancing over the specified number of equal-cost routes.

Press Esc and save your changes.

Press Esc to return to the Internetworking Configuration menu.

Enter a cost for each interface over which you want to balance IPX traffic.

Select the following path:

Select Bindings > a network interface > Expert Bind Options > NLSP Bind Options

Select the Cost Override parameter, enter a value between 1 and 63, then press Enter .

Press Esc and save your changes.

Press Esc to return to the Internetworking Configuration menu.

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

If you want to configure other parameters, do so now, then reinitialize the system when you are finished.