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Integrated IS-IS Commands for CCNP BSCI

Chapter Description

This chapter provides information and commands concerning a wide range of Intermediate System-to-Intermediate System (IS-IS) topics related to the CCNP BSCI exam.

Rules for Creating a NET

  • The NET must begin with a single octet.
  • Addresses starting with 49 (AF I= 49) are considered private IP address, analogous to RFC 1918.
    • — Routed by IS-IS
    • — Should not be advertised to other Connectionless Network Service (CLNS) networks (outside this IS-IS domain)
  • Additional 2 bytes added for the area ID.
  • All routers in the same area must have the same area address.
  • The system ID must be the same number of octets throughout the domain.
  • Cisco has implemented a fixed length of 6 octets for the system ID of a NET.
  • It is customary to use the MAC address of the router, or an IP address of a loopback interface (192.168.111.3 = 192.168.111.003 = 1921.6811.1003).
  • The practice of using a modified loopback IP address as the system ID may now be considered outdated because of the dynamic host name feature. This feature uses a new Type Length Value (TLV 137) to map the router's host name to the system ID.
  • Each device must have a unique system ID within the area.
  • The NET must end with a single octet—the network service access point (NSAP) selector byte (NSEL), usually set to 0x00.
    • — When the NSEL is set to 0, it identifies the device itself.
    • — The NSEL is like a TCP port number: It indicates the transport layer.
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