H3C Technologies H3C S10500 Series Switches - Manual (Page 149)

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IS-IS configuration
NOTE:
The term router in this document refers to both routers and Layer 3 switches.
IS-IS overview
Intermediate System-to-Intermediate System (IS-IS) is a dynamic routing protocol designed by the
International Organization for Standardization (ISO) to operate on the connectionless network protocol
(CLNP).
The IS-IS routing protocol was modified and extended in RFC 1195 by the International Engineer Task
Force (IETF) for application in both TCP/IP and OSI reference models, and the new one is named
“Integrated IS-IS” or “Dual IS-IS”.
IS-IS is an Interior Gateway Protocol (IGP) used within an Autonomous System. It adopts the Shortest Path
First (SPF) algorithm for route calculation.
Basic concepts
IS-IS terminology
• Intermediate system (IS): Similar to a router in TCP/IP, it is the basic unit in IS-IS to generate and
propagate routing information. In the following text, an IS refers to a router.
• End system (ES): Refers to a host system in TCP/IP. ISO defines the ES-IS protocol for communication
between an ES and an IS. An ES does not participate in the IS-IS processing.
• Routing domain (RD): A group of ISs exchanges routing information with each other using the same
routing protocol in a routing domain.
• Area: A unit in a routing domain. The IS-IS protocol allows a routing domain to be divided into
multiple areas.
• Link State Database (LSDB): All link states in the network forms the LSDB. Each IS has at least one
LSDB. The IS uses the SPF algorithm and LSDB to generate its own routes.
• Link State Protocol Data Unit (LSPDU) or Link State Packet (LSP): Each IS can generate an LSP, which
contains all the link state information of the IS.
• Network Protocol Data Unit (NPDU): A network layer protocol packet in OSI, which is equivalent to
an IP packet in TCP/IP.
• Designated IS: On a broadcast network, the designated router is also known as the “designated
IS”.
• Network service access point (NSAP): An NSAP is an OSI network layer address. It identifies an
abstract network service access point and describes the network address in the OSI reference
model.
IS-IS address format
1. NSAP