Summary

This chapter took off from where Chapter 8 left off. We covered link-state routing protocols in detail for the protocols OSPF, NLSP, and IS-IS. All three protocols are similar in many respects with intra-area routing, inter-area routing, hierarchical routing, fast convergence, and scalable support.

OSPF defines its areas as backbone, stub, totally stubby, and standard. LSA types are used to define the exchange of route table updates. The OSPF routing process uses designated routers (DRs) and backup designated routers (BDRs) as central points for information. The router types (internal, backbone, area border router, and autonomous system boundary router) are defined in and between OSPF areas.

NLSP is a replacement to RIP for IPX developed by Novell. Using adjacency, link-state, and forwarding tables, NLSP creates its route tables for exchanging data between routers of intra-area and inter-area routes.

IS-IS is a preferred routing protocol used by ISPs. A two-level hierarchy is used to support large routing domains. Routing within an area is referred to as Level 1 routing; routing between areas is referred to as Level 2 routing. Routers establish Level 1 adjacencies to perform routing within a local area (intra-area routing). Routers establish Level 2 adjacencies to perform routing between Level 1 areas (inter-area routing).

Finally, this chapter introduced bridging and the Spanning-Tree Protocol (STP). We discussed five specific types of bridging and their applications: transparent bridging, source-route bridging, integrated routing and bridging, source-route transparent bridging, and source-route translational bridging. Bridging works at OSI Layer 2 using MAC addresses forwarding and filtering frames. Loop avoidance is managed by the Spanning-Tree Protocol as defined by the IEEE 802.1d.