Content

| Summary

Once this module is complete, the student should have a firm understanding of the following concepts:

- CLNS addressing
- IS-IS operation in a CLNS environment
- Types and functions of PDUs in IS-IS routing
- Integrated IS-IS operation in an IP and CLNS environment
- Default behavior of Integrated IS-IS routing and the role of the attached bit, the overload bit, and route leaking
- Integrated IS-IS in an NBMA environment
- Configuration of IS-IS in single and multiple areas, L1 and L2 circuit types, authentication, and route summarization
- Monitoring an Integrated IS-IS network with show and debug commands

IS-IS is a versatile routing protocol used in many very large ISPs. The natural scalability of IS-IS makes it a great choice for modern large-scale IGP network deployments. IS-IS uses the SPF algorithm, just as OSPF, but requires less SPF calculations as a result of its ability to handle PRCs. IS-IS has established a firm foothold in many networks comprising the Internet and it will not be surprising if its presence expands in the years to come.