NLSP is a link state interior gateway protocol for IPX networks. NLSP, which is based on the OSI Intermediate System-to-Intermediate System (IS-IS) protocol, has features similar to those of other link state protocols, such as OSPF. Like other link state protocols, NLSP supports hierarchical addressing and fast convergence.
NLSP has the capability to use hierarchical routing techniques to aggregate and summarize IPX network numbers . Route aggregation and summarization are useful in large IPX networks for the same reasons they are useful in large IP networks.
The first level in NLSP routing is an area . An NLSP area is a logical group of IPX network addresses; it is conceptually similar to an OSPF area, which is a collection of IP networks and subnets. NLSP Level 1 routing occurs within an area. NLSP communication between areas is called Level 2 routing . You can group all areas with NLSP routers communicating with Level 2 routing into a hierarchical collection called a routing domain . NLSP communication between routing domains is Level 3 routing . Figure 6-3 shows an NLSP internetwork.
Figure 6-3. The Hierarchical Structure of an NLSP IPX Network
NLSP requires an internal IPX network number to be configured on a Cisco router. You can do so by using the IOS global configuration command ipx internal-network , as noted earlier in this chapter in the "IPX Addressing and Address Structure" section.
To enable NLSP, use the IOS global configuration command ipx router nlsp . This configuration command requires that a tag parameter be used to specify the NLSP process in the IOS. To define a set of network numbers as part of the current NLSP area, use the area-address IOS global configuration command. The area-address command takes two options, an IPX network address and a mask. The mask indicates how much of the area number identifies the area and how much of that number identifies individual networks in the area. Although we do not use NLSP in the ZIP network, the following example shows the enabling of NLSP on the Singapore router. The following use of the area-address command describes an area of 16 networks in the range of 4000 through 400F:
Singapore# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. Singapore(config)# ipx router nlsp 1 Singapore(config-ipx-router)# area-address 4000 FFF0 Singapore(config-ipx-router)# ^Z
NLSP needs to be enabled on a per-interface basis using the IOS interface subcommand ipx nlsp enable . This configuration command specifies the NLSP process tag to use when sending routing information on a given interface. We enable NLSP process 1 on the Singapore router's interface Ethernet 0 in the following example:
Singapore# configure Configuring from terminal, memory, or network [terminal]? Enter configuration commands, one per line. End with CTRL+Z. Singapore(config)# interface ethernet 0 Singapore(config-if)# ipx nlsp 1 enable Singapore(config-if)# ^Z