Integrated Intermediate System-to-Intermediate System
Integrated IS-IS is a link-state routing protocol, but few people consider it an alternative to OSPF. Even so, IS-IS is a common routing protocol typically used in large ISP environments. IS-IS was developed at the same time OSPF was being developed. In brief, IS-IS was designed to provide two routing mechanisms (in competition with OSPF forum, which could only route IP) at the same time: one for IP and another for Decnet Phase V. This chapter covers integrated IS-IS IP routing capabilities only.
As with any new protocol, you need to be familiar with some new terms and definitions to fully understand IS-IS. Instead of using areas as OSPF does, IS-IS has routers perform Level 1 (L1) and Level ...
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