• ICMP Router Discovery Overview
• MPLS Overview for ACX Series Universal Access Routers on page 587
• Configuring Junos OS for IPv6 Path MTU Discovery
• IPv6 Neighbor Discovery Overview
IS-IS Overview
The IS-IS protocol is an interior gateway protocol (IGP) that uses link-state information
to make routing decisions.
IS-IS is a link-state IGP that uses the shortest-path-first (SPF) algorithm to determine
routes. IS-IS evaluates the topology changes and determines whether to perform a full
SPF recalculation or a partial route calculation (PRC). This protocol originally was
developed for routing International Organization for Standardization (ISO) Connectionless
Network Protocol (CLNP) packets.
Like OSPF routing, IS-IS uses hello packets that allow network convergence to occur
quickly when network changes are detected. IS-IS uses the SPF algorithm to determine
routes. Using SPF, IS-IS evaluates network topology changes and determines if a full or
partial route calculation is required.
NOTE: Because IS-IS uses ISO addresses, the configuration of IP version 6
(IPv6) and IP version 4 (IPv4) implementations of IS-IS is identical.
NOTE: See Platforms/FPCs That Cannot Forward TCC Encapsulated ISO
Traffic to find a list of those devices and FPC configurations that cannot pass
ISO traffic when encapsulated in TCC format.
This section discusses the following topics:
•
IS-IS Terminology on page 536
•
ISO Network Addresses on page 537
•
IS-IS Packets on page 539
•
Persistent Route Reachability on page 540
•
IS-IS Support for Multipoint Network Clouds on page 540
•
Installing a Default Route to the Nearest Routing Device That Operates at Both IS-IS
Levels on page 540
IS-IS Terminology
An IS-IS network is a single autonomous system (AS), also called a routing domain, that
consists of end systems and intermediate systems. End systems are network entities that
send and receive packets. Intermediate systems send and receive packets and relay
Copyright © 2017, Juniper Networks, Inc.536
ACX Series Universal Access Router Configuration Guide
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