System information

CHAPTER
Troubleshooting ISO CLNS 12-271
12
Troubleshooting ISO CLNS
This chapter presents protocol-related troubleshooting information for International Organization
for Standardization (ISO) Connectionless Network Service (CLNS) protocol connectivity and
performance problems. ISO CLNS is a network layer standard that is part of the Open System
Interconnection (OSI) protocol suite.
The Cisco IOS software supports packet forwarding and routing for ISO CLNS on networks using
a variety of data link layers: Ethernet, Token Ring, Fiber Distributed Data Interface (FDDI), and
serial. You can use CLNS routing on serial interfaces with High-Level Data Link Control (HDLC),
Point-to-Point Protocol (PPP), Link Access Procedure, Balanced (LAPB), X.25, Switched
Multimegabit Data Service (SMDS), or Frame Relay encapsulation. To use HDLC encapsulation,
you must have a router at both ends of the link. If you use X.25 encapsulation, you must manually
enter the network service access point (NSAP)-to-X.121 mapping. The LAPB, X.25, Frame Relay,
and SMDS encapsulations interoperate with other vendors.
Cisco’s CLNS implementation is also compliant with the Government Open Systems
Interconnection Profile (GOSIP) Version 2. As part of its CLNS support, Cisco routers fully support
the following ISO and American National Standards Institute (ANSI) standards:
• ISO 9542—Documents the End System-to-Intermediate System (ES-IS) routing exchange
protocol.
• ISO 8473—Documents the ISO Connectionless Network Protocol (CLNP).
• ISO 8348/Ad2—Documents NSAP addresses.
• ISO 10589—Documents Intermediate System-to-Intermediate System (IS-IS) Intra-domain
Routing Exchange Protocol.
Both the ISO-developed IS-IS routing protocol and Cisco’s ISO Interior Gateway Routing Protocol
(IGRP) are supported for dynamic routing of ISO CLNS. In addition, static routing for ISO CLNS
is supported.
ISO CLNS Technology Basics
The world of OSI networking has a unique terminology:
• End system (ES) refers to any nonrouting network device.
• Intermediate system (IS) refers to a router.
• Area is a group of contiguous networks and attached hosts that are specified by a network
administrator or manager to be an area.
• Domain is a collection of connected areas. Routing domains provide full connectivity to all end
systems within them.