IS-IS configuration
NOTE:
The term
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The 3600 v2 SI Switch Series does not support IS-IS.
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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 1 195 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
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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
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between an ES and an IS. An ES does not participate in the IS-IS processing.
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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
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multiple areas.
Link State Database (LSDB): All link states in the network forms the LSDB. Each IS has at least one
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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
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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
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an IP packet in TCP/IP.
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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
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abstract network service access point and describes the network address in the OSI reference
model.
router
in this document refers to both routers and Layer 3 switches.
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