Information Technology Reference
In-Depth Information
12
CHAPTER
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.
•
