Baseline Model of the Network

In order to be able to effectively support, troubleshoot, or modify an internetwork, you have to gather and maintain a certain amount of information about it. The following list includes some of the essential information recommended for inclusion in your ongoing (consistently updated) network documentation The physical and logical map of your network The addressing scheme (protocol specific) Network's baseline traffic and performance statistics and measurements about your internetwork and its...

Problem Solving Model

A generally accepted troubleshooting model is presented in Figure 2-1. This model presents a process flow that can effectively guide you during your troubleshooting tasks. Most organizations have a standard method like this one in place. One important benefit of this model is that as you solve your problems, you are also adding to your knowledge and skill set. Furthermore, each time a troubleshooting task is completed, all the gathered data and actions taken are recorded for future reference....

Apple Talk Configuration and Troubleshooting Checklist

This section will review the basic requirements for a trouble-free AppleTalk network. Even though network configurations vary from one organization to another, the essential settings needed per the protocol suite's specifications remain the same. The following list specifies those basic requirements All routers connected to a network must agree on the configuration of that network. Those routers (connected to a single cable segment) must have identical settings with regard to network numbers...

B

B channels (ISDN), displaying status, 375 baselining, 41 Notification), 313 BRI (Basic Rate Interface) interface D channel, 351 Layer 1, 352 PUP timer, 353-354 T3 timer, 353-354 Layer 2, 355, 357 activating, 358-360 INFO frames, 360 LAPD frame format, 357 RR messages, 359 Layer 3, 365, 367 call rejection, 371 SPID numbers, 369-371 Browser service (Windows), Cisco 7000 series routers, 130-132 sizes of, 129 Bug Toolkit (CCO), 18-19 distance limitations, 246-247 testers, 6 troubleshooting, 246...

Book Layout

This final section of the introduction covers briefly the contents of each chapter in the book. Chapter 1 covers three main topics. First, it lists and introduces you to a number of troubleshooting tools that are adequate for testing different aspects or components of an internetworking model. You must learn when and why each tool is used, and what information may be obtained from each. Next, Cisco Connection Online is introduced. You should know who can access CCO and how. Familiarity with the...

Buffers and Queues

System buffers are memory allocated from main system memory (also referred to as shared memory) to hold packets while they are process-switched. There are parameters regarding these buffers that can be tuned, but that is not often recommended, and tuning them has no effect on any route caching methods you may have (fast, autonomous, silicon, or optimum switching, for instance). To enhance the (packet) processing power of your router, you are usually encouraged to take advantage of your router's...

Buffers and Queues Cisco 70007010

In the Cisco 7000, routers' packets are held in interface hardware buffers, SP or SSP buffers, and RP buffers. Figure 4-6 displays those Cisco 7000 router components along with the error conditions associated with each of them. Figure 4-6 Cisco 7000 Buffers and Error Conditions Interface input and output queues on the RP are linked lists of processor buffers used for each interface. An interface queue can hence be composed of different-sized buffers. The queue associated with an interface can...

Cable Speed and Media Concerns

The link LED on each individual port of the Catalyst 5000 switch is of great value to you. If this LED, which is often referred to as port integrity LED, is not green on both sides of a connection, you have a problem. If either side is not powered up, has the port disabled, or does not have the cable properly inserted, or if the cable is simply broken, substandard, badly bent or otherwise abused, the link integrity LED does not come on. Hence, checking to make sure that both sides of a link...

Catalyst 5000 Spanning Tree

You need to be aware of certain facts regarding the operation and behavior of Spanning Tree in Catalyst 5000 switches. The Catalyst 5000 series use IEEE 802.1D Spanning-Tree Protocol. There will be one Spanning Tree per VLAN on a switch. The Spanning Tree corresponding to a particular VLAN is usually enabled on every port that is assigned to that VLAN. However, certain ports that connect to work stations may be in Port-Fast mode or have the Spanning Tree disabled on them. A port that is...

CCNP Support Exam Certification Guide

CCNP Support Exam Certification Guide Copyright 2001 Cisco Systems, Inc. Cisco Press logo is a trademark of Cisco Systems, Inc. Published by Cisco Press 201 West 103rd Street Indianapolis, IN 46290 USA All rights reserved. No part of this book may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the publisher, except for the inclusion of brief...

CCO Bug Toolkit

The Bug Toolkit is a set of tools including the Bug Navigator II, Bug Watcher, and watcher agents, all of which are made available to registered users on CCO from one place www.cisco.com support bugtools (see Figure 1-7). If you experience abnormal behavior in your network, or are thinking of upgrading your IOS, you can search for reported defects based on IOS version release number or keywords related to the symptoms you have observed or the technology you are concerned with. Next, you can see...

CCO Open Forum

The CCO Open Forum (www.cisco.com openf ), as the name implies, is an online Q& A facility that Cisco Systems has provided for its customers. If you have a technical question that relates to Cisco Systems products (hardware or software), you can use the Open Forum (see Figure 1-9) to look for your answer in two ways By searching the existing Q& A database By submitting your question to the Open Forum (if you could not find your answer in the current database) As is indicated in the Open...

CCO Stack Decoder

Stack Decoder (see Figure 1-8) is another troubleshooting tool available at CCO (www.cisco.com stack). This tool is used when a router crashes it decodes the stack trace generated by Cisco routers and switches. If you execute the privileged command show stack from the exec prompt of the router, the stack trace appears. Next, you can paste the results in the input field of the Stack Decoder page. Stack Decoder decodes the stack trace and creates a symbol file. The symbol file (perhaps along with...

Support Resources for Troubleshooting S

Do I Know This Already Quiz 3 Network Management Systems 10 CiscoWorks 11 CiscoWorks for Switched Internetworks Software 12 TrafficDirector Remote Monitoring Software 12 Using CCO to Prevent Problems 15 Cisco Documentation CD-ROM 15 Cisco MarketPlace 16 CCO Software Library 17 Using CCO to Correct Problems 18 CCO Bug Toolkit 18 CCO Troubleshooting Engine 20 CCO Stack Decoder 20 CCO Open Forum 20 Escalation to Cisco Service and Support 22 CCO Case Management Toolkit 23

Diagnosing and Correcting Frame Relay Problems 307

Do I Know This Already Quiz 307 Frame Relay Troubleshooting (Checklist) 311 The IETF Frame Structure for Frame Relay 312 The Frame Relay Diagnostic Tools show 313 show interface serial n 313 Frame Relay Loopback Testing 317 show frame-relay lmi interface 319 show frame-relay map 320 show frame-relay pvc 321 The Frame Relay Diagnostic Tools debug 322 debug serial interface 323 debug frame-relay lmi 324 The debug frame-relay and the debug frame-relay events Commands 325 debug frame-relay packet...

Diagnosing and Correcting Catalyst Problems 241

Do I Know This Already Quiz 241 Foundation Topics 244 CiscoWorks for Switched Internetworks (CWSI) 244 Embedded RMON Agent and SwitchProbe 244 Cable, Speed, and Media Concerns 246 Troubleshooting Catalyst 5000 Trunking VTP and ISL 249 Catalyst 5000 Switch Diagnostic Tools ping and CDP 251 Catalyst 5000 Switch Diagnostic Tools show Commands 253 set and clear Commands 254 The show system Command 254 The show test Command 255 The show interface Command 258 The show log Command 259 The show mac...

Cisco Discovery Protocol

Cisco Discovery Protocol (CDP) is a Cisco proprietary layer 2 (data link layer) protocol that is bundled in Cisco IOS release 10.3 and later versions. This protocol can run on all Cisco manufactured devices including routers, switches, hubs, bridges, and communication servers. CDP uses SNAP (layer 2 frame type) and it is multicast based, utilizing the Cisco multicast address 0100.0ccc.cccc as the destination address on the frame header. Because a Cisco device running CDP periodically sends...

Cisco Documentation CDROM

Cisco Documentation is an interactive library of technical information provided on CCO. Figure 1-5 shows the Cisco Documentation home page on CCO. Figure 1-5 Cisco Documentation on CCO Figure 1-5 Cisco Documentation on CCO We welcome your feedback on this product. About the Documentation CD-ROM A complete UserCuide for Che Do ( mentation CD-ROM. Welcome D o cumentation Roadmap Using this CD-ROM Cisco Service and Support Cisco Product Documentation Cisco IOS Software C onfiguration Internet...

Cisco Market Place

The Cisco MarketPlace is the page on CCO through which you can order Cisco networking products, promotional merchandise, and training materials (see Figure 1-6). Since they save time and money, shorten lead times, and improve efficiency, Internet commerce applications are now very popular. To order direct from Cisco using the Internet commerce applications, you need to perform the following 1 Obtain a valid Cisco purchase order or sales order number for your company, as well as your company...

Cisco Press Fundamentals

IP Routing Primer Robert Wright, CCIE 1-57870-108-2 AVAILABLE NOW Learn how IP routing behaves in a Cisco router environment. In addition to teaching the core fundamentals, this book enhances your ability to troubleshoot IP routing problems yourself, often eliminating the need to call for additional technical support. The information is presented in an approachable, workbook-type format with dozens of detailed illustrations and real-life scenarios integrated throughout. Allan Leinwand, Bruce...

Cisco Press Solutions

EIGRP Network Design Solutions Ivan Pepelnjak, CCIE 1-57870-165-1 AVAILABLE NOW EIGRP Network Design Solutions uses case studies and real-world configuration examples to help you gain an in-depth understanding of the issues involved in designing, deploying, and managing EIGRP-based networks. This book details proper designs that can be used to build large and scalable EIGRP-based networks and documents possible ways each EIGRP feature can be used in network design, implmentation,...

Cisco Routers Routing Processes and Switching Processes

Routing and switching processes are two of the most essential tasks performed by routers. Some people in the internetworking field have a little difficulty with the idea that routers perform switching, but of course everybody is comfortable with the fact that routers perform routing. Nonetheless, as you will see, the distinctions between these operations will be quite useful in optimizing the router's performance. In the following paragraphs the concepts of routing and switching are defined. A...

Clearing Interface Counters

If you suspect interface problems, the output of the show interfaces command gives you a great amount of information about the state of the interface (physical and logical) and also some statistics about the data sent and received, errors encountered, and so on. Consider Example 3-1 for this discussion. Seriall is up, line protocol is up Hardware is HD64570 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usee, rely 255 255, load 1 255 Encapsulation FRAME-RELAY, loopback not set, keepalive set (10 sec)...

Common Apple Talk Trouble Symptoms Possible Causes and Suggested Actions

This section concentrates on common errors and misconfigurations related to AppleTalk settings, the expected symptoms of each problem, and how you can identify the exact reason for the symptoms and rectify the situation. The most common faults found in AppleTalk networks are Configuration mismatch Neighboring routers do not have identical specifications for the cable range and zone name(s) of the segment they have in common. Duplicate cable range network numbers or overlapping cable ranges in...

Common Protocol Characteristics

Network protocols are divided into two classes based on their characteristics Connection-oriented protocols Connection-oriented protocols are those that establish an end-to-end connection before submitting data. The sequence of steps performed by a connection-oriented protocol is as follows Step 2 Send (and perhaps receive) data. Step 3 Terminate (tear down) the connection. Most of the connection-oriented protocols are also reliable in other words, they also guarantee delivery of the data...

Contents at a Glance

Support Resources for Troubleshooting 3 Understanding Troubleshooting Methods 33 Identifying Troubleshooting Targets 49 Applying Cisco Troubleshooting Tools 101 Diagnosing and Correcting Campus TCP IP Problems 159 Diagnosing and Correcting Novell Networking Problems 189 Diagnosing and Correcting AppleTalk Problems 215 Diagnosing and Correcting Catalyst Problems 241 Troubleshooting VLANS on Routers and Switches 285 Diagnosing and Correcting Frame Relay Problems 307 Diagnosing and Correcting ISDN...

Debug apple Commands

Using debug commands requires special attention. You should try to use the debug apple commands when the traffic in your network is low. Some debug commands can produce a large amount of output hence, you are encouraged to do events debugging when you can. Example 7-10 displays the debug apple options. This section contains brief explanations for the following significant debug apple commands Please note that the keywork apple used with the debug commands listed is not a truncated form of...

Debug apple events

The debug apple events command is one of the most informative debug commands used for troubleshooting AppleTalk networks, yet it imposes less overhead than other commands such as debug apple packet. In a stable network, this command does not produce any information. The debug apple events command logs messages only about AppleTalk special events such as route changes, neighbors becoming reachable or unreachable, and interfaces going up or down. You may monitor state changes for instance, those...

Debug apple nbp

Use the debug apple nbp command to see debugging output about NBP activities. If you want to find out why your router is not receiving NBP lookups from a node, enable this command and, starting from the router closest to the node in question, move towards your own router until you find out where the lookups are being dropped (filtered or otherwise mishandled). Cisco documentation warns that since this debug command can generate many messages, it should be used only when the router's CPU...

Debug apple zip

The debug apple zip command is used to see information pertaining to the activities of the Zone Information Protocol (ZIP). The information displayed by this command includes significant events such as discovery of new zones and zone list queries. You may use the debug apple zip command to find out if a ZIP storm is taking place. A ZIP storm is a situation where none of the routers has the zone name corresponding to a network number that exists in all the routers' routing tables. This can...

Debug arp

When debug arp is in use, the router displays all the ARP-related traffic (requests and responses) that the router itself or hosts on the local segment(s) generate. You can monitor the ARP replies to see if they are expected or faulty. Routers normally filter ARP replies that they see as meaningless. Use this command to find out which nodes on a TCP IP network are and which ones are not responding to ARP requests. You can also monitor if your router is sending or receiving ARPs. NOTE Since an...

Debug framerelay lmi

When you execute the debug frame-relay lmi command, you should see the status enq. (inquiry) that your router sends out every 10 seconds and the status message (type 1) that your router receives (in) from the Frame Relay switch every 10 seconds (see Example 109). Also, every 60 seconds the switch sends a FULL LMI message to your router (type 0), which includes a list of PVC DLCIs along with the status of each DLCI and its corresponding CIR (Committed Information Rate). The status of each DLCI...

Debug framerelay packet

The debug frame-relay packet command displays the packets that have been sent (out) on a Frame Relay interface (see Example 10-12). This command helps you to analyze the packets that have been sent on a Frame Relay interface. Because the debug frame-relay packet command generates large amount of output, the Cisco Documentation CD suggests that you use it only when traffic on the Frame Relay network is less than 25 packets per second. Example 10-12 A Sample Output of the debug frame-relay packet...

Debug IP Commands

There are many debug IP commands that can be used during the course of a troubleshooting project (see Example 5-6). You must keep in mind that some of the debug commands generate a lot of output, and that usage of the debug command requires special handling (as discussed in Chapter 4, Applying Cisco Troubleshooting Tools). Use the Debug reference manual (also available on Cisco Connection Online CCO and the Documentation CD) for the IOS version you work with. To display the state of each...

Debug ip eigrp

The debug ip eigrp command displays the Enhanced IGRP packets sent and received on your router interfaces. This command produces a lot of output, which can be dangerous in a large and busy network. The top portion of Example 5-12 displays the optional parameters you can specify along with this command. The second portion of Example 5-12 displays sample output of the debug ip eigrp command. Use this command and the optional parameters to troubleshoot the Enhanced IGRP routing protocol. Example...

Debug ip igrp events

Debug ip igrp events ip-address This debug command displays summary information on sent and received Interior Gateway Routing Protocol (IGRP) routing messages (see Example 5-10). The source and destination of each update as well as the number of routes in each update are indicated for each message. This command does not display the actual IGRP routing entries that are exchanged. If you specify the IP address (optional) of a neighbor router (which is an IGRP peer), IGRP event debugging will only...

Debug ip igrp transactions

Debug ip igrp transactions ip-address This debug command displays information on Interior Gateway Routing Protocol (IGRP) routing transactions. Example 5-11 shows that the router being debugged sent updates to the broadcast address (255.255.255.255) via ethernet 0 and ethernet 1 interfaces, and it has received an update from a router with the IP address 131.1.18.14 on ethernet 0 interface. Notice that with IGRP transaction debugging the content (routing entries exchanged) of the updates that...

Debug ip ospf

The debug ip ospf command is used with one of the following options adj, events, flood, lsa-generation, packet, retransmission, spf, or tree (see top portion of Example 5-13). The debug ip ospf command with the events option displays information on OSPF (Open Shortest Path First) events, such as adjacencies, flooding information, designated router and backup designated router election, and shortest path first (SPF) calculation. Sample output of the debug ip ospf events is shown in the bottom...

Debug ip packet

Debug ip packet detail access-list-number The debug ip packet command is useful for analyzing the flow of IP packets traveling between IP hosts. IP debugging information includes packets received, generated, and forwarded. As discussed in Chapter 4, you have the option to specify an access list number or name after the debug IP packet command to limit the scope of debug output (see Example 5-7). Example 5-7 Various debug IP Examples < 1-199> Access list < cr> events RIP protocol events...

Debug ip rip

This debug command displays information about RIP routing transactions. You may specify the events optional keyword if you are only interested in seeing RIP protocol events. Example 5-9 shows updates being received (RIP version 1) from a router with source address 131.1.18.14. The router being debugged also sent updates, in both cases to broadcast address 255.255.255.255 as the destination. Note that if an interface's broadcast address is modified, then information such as distance vector...

Debug ipx eigrp

The debug ipx eigrp command is used to display the packets an EIGRP routing process sends and receives during its operation. With this command you may use the events option or the neighbor option (see Example 6-10). The events option gives you less information, but it has less overhead for the router. Example 6-10 debug ipx eigrp Command Example 6-10 debug ipx eigrp Command (Continued)

Debug ipx nlsp

The debug ipx nlsp command is a powerful tool for troubleshooting or monitoring the behavior of an NLSP routing process. With this command you may enter one of many available optional parameters to focus your debug on specific activities such as protocol errors, adjacency, or update packets (see Example 6-11). Example 6-11 debug ipx nlsp Command

Debug ipx routing

The debug ipx routing command is used with one of the activity or events options, and it displays information on IPX-related routing (RIP) traffic that the router generates and also receives (see Example 6-9). Use this debug command when you are interested in seeing the IPX routing information your router sends out of and receives from each interface. Example 6-9 debug ipx routing Command activity IPX RIP routing activity events IPX RIP routing events

Debug ipx sap

The debug ipx sap command displays information about IPX Service Advertisement Protocol (SAP) packets your router sends and receives. You may use the debug ipx sap command with the activity or the events option. To understand the output of this command, you need to be aware of the following Each IPX packet that carries SAP has a source and destination IPX address and socket number. Each IPX packet may contain up to seven SAP entries. The SAP Update-Type and SAP Response-Type (displayed for each...

Debug serial interface

This command is not limited to troubleshooting Frame Relay only. Indeed, any serial interface can be diagnosed with this command. If a serial interface is operating properly and is exchanging keepalives with the switch that it is connected to, the debug serial interface displays the keepalives that are being sent and received. If anything goes wrong and the exchange of keepalives gets interrupted, the debug serial interface displays a message that with luck will lead you to the cause. Example...

Debug span tree and debug span events

The debug span command can be used with either the tree or the events parameter. The events option is more user-friendly because it tells you in words the meaning of the BPDU packets that the router is receiving (see Example 9-7). The tree option, on the other hand, displays each BPDU received from each interface in its raw format. For instance, the first entry in the output of the debug span tree (Example 9-7) shows the following line 00 15 42 ST Fa0.100 00000080. This line tells you that at 3...

Debug vlan packets

The debug vlan packet command displays messages about virtual LAN (VLAN) packets that the router receives (off the trunk connection) but is not configured to support (see Example 9-6). In other words, if an ISL packet with a VLAN ID of 6 is received, but none of the subinterfaces of the input interface are configured for VLAN 6, the router cannot process the encapsulated frame and the debug process displays a message indicating what has just happened. As mentioned earlier, you may use the show...

Diagnosing and Correcting Apple Talk Problems

Based on the assumption that you have a basic understanding of the AppleTalk protocol suite, this chapter will present a set of troubleshooting commands, tools, techniques, and tips that are essential for supporting AppleTalk networks. The commands and tools presented here are often used to isolate the problem area and determine the exact source of the problem. The AppleTalk Configuration and Troubleshooting Check List section summarizes the requirements for a working AppleTalk network. Also,...

Diagnosing and Correcting Frame Relay Problems

Frame Relay is a connection-oriented OSI Layer 2 protocol. Frame Relay fits in the packet-switching category for wide-area network technology. Currently most of the implementations use permanent virtual circuits (PVCs) to connect remote offices, and many organizations are testing switched virtual circuits (SVCs). This chapter's focus is on diagnosing and correcting Frame Relay PVC networking on Cisco serial interfaces. Even though the chapter is not intended to provide a course on Frame Relay...

Diagnosing and Correcting Isdn Bri Problems

ISDN is a circuit-switched wide-area service that provides end-to-end digital connection between remote devices. Similarly to other WAN services, the ISDN service is used to provide connectivity between remote offices through a service provider's network. The physical devices and media that provide this complete connectivity fall into one of three categories customer premises equipment (CPE), local access loops, and service provider networks. The communication between these devices is a...

Do I Know This Already Quiz

If you wish to evaluate your knowledge of the contents of this chapter before you get started, answer the following questions. The answers are provided in Appendix A, Answers to Quiz Questions. If you are having difficulty providing correct answers, you should thoroughly review the entire chapter. If all or most of your answers are correct, you might want to skim this chapter for only those subjects you need to review. You can also use the Foundation Summary section to quickly review topics....

E

EIGRP (Enhanced Interior Gateway Routing Protocol), troubleshooting, 174 embedded RMON agent, Catalyst 5000 switches, 245 encapsulation frame relay command, 311 encapsulation isl command, 290 end-to-end circuits, ISDN, 372 PPP over B channel, 374-376 end-to-end connections (Frame Relay), troubleshooting, 317-319 error messages AppleTalk, debugging, 225-226 logging, 117-120 establishing connections AppleTalk, 82 Novell, 80 TCP, 78-79 Ethernet interfaces, troubleshooting, 54-61 evaluating links,...

Error Message Logging and Limiting the Display of Error Messages

Logging messages are important sources of information for network engineers in charge of troubleshooting. This section covers the following topics The options for the logging messages destination Which destinations are the default for logging messages Which commands enable disable different destinations How usage of different logging destinations compares with regard to the overhead they introduce on the routers The eight levels of logging Deciphering the logging messages Message logging is...

Foundation Summary

The Foundation Summary is a collection of quick reference information that provides a convenient review of many key concepts in this chapter. For those of you who already feel comfortable with the topics in this chapter, this summary helps you recall a few details. For those of you who just read this chapter, this review should help solidify some key facts. For any of you doing your final prep before the exam, these tables and figures are a convenient way to review the day before the exam....

Foundation Topics Cisco Works for Switched Internetworks CWSI

CWSI (the Campus version) is a suite of network management applications that together provide remote monitoring, configuration, and management of switched internetworks. The following applications are included in the CWSI Campus package These management applications can be used to build the network baseline, identify problem areas (or components), and reconfigure devices from a central point using a GUI (graphical user interface). CiscoView allows you to view a device's chassis, configuration,...

Foundation Topics Frame Relay Troubleshooting Checklist

There are some steps that you need to be aware of and make sure are in effect with respect to the configuration of the Cisco routers involved in a Frame Relay connection. One of the very basic commands that needs to be entered in the interface configuration mode is As you can see, with this command you have the option to specify the IETF frame type. If you do not enter the ietf optional parameter, the IOS implements the cisco frame type. In other words, cisco is the default frame type on the...

Foundation Topics Network Media Test Equipment

There are three classes of equipment for testing the physical layer medium Volt Ohm meters and digital multimeters The parameters tested by this equipment are voltage, current, resistance, and capacitance. In fact, the purpose of using these products is to check for cable connectivity and continuity. These devices are usually very affordable, but one who uses them must be familiar with the specifications of the medium being tested. For example, if you use a Volt Ohm meter to test a 10Base2...

Frame Relay Loopback Testing

Loopback testing is a commonly employed technique to identify the exact problem area in an end-to-end connection such as a Frame Relay. The end-to-end Frame Relay connection comprises the following segments The segment between the local router and its CSU (local CPE) The segment between the local CSU and the service provider's switch (local loop) The Frame Relay network (the WAN cloud) The segment between the remote CSU and the service provider's switch at the remote location The segment...

Frame Relay Problem Isolation

To check diagnose a Frame Relay connection, you must perform the following tests (using the troubleshooting commands you have learned) in sequence Check the status of your router's (Frame Relay) serial interface (for example, Serial 1 interface) using the show interface serial n command. The output must show If serial 1 is down, you must check and correct the connection between your router's serial interface and the CSU. If the serial interface is up and the line protocol is down, either the...

Handling the Cisco IOS Debug Troubleshooting Tool

Debug is a troubleshooting command that is available from the privileged exec mode (of Cisco IOS). This command can be used to display information about various router operations and the related traffic generated or received by the router, as well as any error messages. This tool is very useful and informative, but you must be aware of the following facts regarding its use Debug is treated as a very high priority task. It can consume a significant amount of resources, and the router is forced...

Information Needed by Technical Support

In some troubleshooting cases you have to seek assistance from Cisco Technical Support. When customer support engineers (CSE) at Cisco Systems open a case, they need a set of information from a caller. The following paragraphs list and describe different types of information to furnish to the CSEs. You must identify your company and your service arrangement. Next, you have to provide a statement of your problem, a brief history of the problem, a list of reported symptoms, an indication of how...

N

Navigating Cisco Documentation CD-ROM, 16 NBP (Name Binding Protocol), debugging, 226 nbtstat command, 178 NCP (Novell Core Protocol), 80 NetBIOS cache, displaying, 178 Netflow switching, 112 Netsys, 13 network management systems. See NMSs network maps, STP, 294 network monitors, 7 Network Neighborhood Browser service, troubleshooting, 180 network protocols, characteristics, 77 networks baselining, 41 media testing equipment, 6 modeling simulation tools, 13 NMSs (Network Management Systems), 10...

Netflow Switching

Netflow switching was introduced with Cisco IOS version 11.1(2) for the Cisco 7000, 7200, and 7500 routers with an RSP (Cisco offers the RSP7000 card for the 7000 routers). Netflow identifies a flow based on the source and destination IP address, source and destination port, protocol type (number), type of service (TOS), and input interface. The other switching types keep network layer destination address and output interface pairs in the cache. If a packet's destination address matches an...

Network Monitors

Network monitors were first built to capture, display, and save traffic going through a network cable. Since frames are captured, and the information gathered and displayed is pertaining to the data link layer, this tool is considered a Layer 2 tool. Of course, many vendors created different brands and models of this tool with different capabilities. The most common feature of network monitors is their ability to take the raw data and provide some summarization and statistics for the user....

Ping and Trace

Ping is a standard application included as a part of the TCP IP protocol suite. From a particular IP host, you can use ping to test reachability of another IP host. On Cisco routers, a simple ping is provided in user mode but in privileged exec mode, an extended ping is also provided, which offers more testing options. For instance, with the extended ping you may specify the source address, packet size, repeat count, timeout, and data pattern. Trace is also a testing application that is usually...

Ping Command IP User and Privileged

The ping command is supported at the user and privileged exec modes.When used at the user mode, a set of default parameters such as five echoes, 100 bytes each with two-second time-outs will be used (in non-verbose form). You may enter an IP address or a name with the ping command (if the name can be resolved to an IP address using the local HOSTS table or using a DNS server). Ping sends ICMP echo (echo request) to the destination, and the destination node replies to the source with an ICMP...

PPP over B Channel

Before PPP starts delivering upper layer protocol packets between two devices, it goes through a series of negotiations regarding link options and network protocols. The PPP frame format is shown in Figure 11-6. During link options negotiation, the PPP frame's protocol number is 0xC021 (LCP). LCP negotiates link options such as Authentication, Multilinking, Callback, Compression, and line Quality Protocol. For a link option to be implemented, both parties must agree on it. Disagreement on a...

Problem Isolation in Router Switch VLAN Networks

To ensure that a router is properly connected to a switch through a trunk and that it is receiving the desired data units and processing them, you need to do the following Check the physical link between the router and the switch. For instance, make sure that the cable between the router and switch is straight-through, is of the correct type category, and is properly connected using proper connectors. The LEDs and the output of appropriate show commands can help you determine the state of the...

Qa

The answers to the following questions can be found in Appendix A. Some of the questions in this section are repeated from the Do I Know This Already Quiz so that you can gauge the advancement of your knowledge of this subject matter. 1 Write the title of each of the systematic troubleshooting method's steps in the appropriate box on the diagram below 2 Explain the importance of using a systematic troubleshooting method. 3 What are the general tasks performed during the problem definition step...

Reported Conditions

Ignored The number of packets ignored is shown in the output of the show interfaces command. If a buffer (on the interface hardware) gets full, an ignore is registered. In other words, every time an interface cannot accept a frame due to the input buffer being full, the ignore counter is incremented by one. Dropped The number of dropped packets is shown in the output of the show interfaces command. If the input or output queue of an interface reaches its maximum size, the queue cannot grow...

Review of ISDN Troubleshooting Commands

Figure 11-7 displays some of the commands that are used for ISDN troubleshooting. This figure also illustrates which commands are more appropriate for testing specific segments of the ISDN connection (or layer). You are advised to study this figure thoroughly. Figure 11-7 Review of ISDN Troubleshooting Commands debug serial interface debug bri-interface debug ppp negotiation debug isdn q931 debug ppp chap

Route Caching Methods and Commands

Route caching methods available in different Cisco router series and the commands to enable them are displayed in Table 4-10 (to disable any of these switching modes, use the no form of the command) Table 4-10 Route Caching Methods and Commands Route Caching (Switching) Method Enabled Fast switching and autonomous switching

S

Seed metric, applying to routing protocols, 180 Service Profile Identifier numbers. See SPID numbers set command (Catalyst), 254 set vtp command, 251 severity of logging messages, 120 show appletalk access-lists command, 221 show appletalk adjacent-routes command, 221-222 show appletalk arp command, 222 show appletalk globals command, 222, 228 show appletalk interface command, 219 show appletalk name-cache command, 223 show appletalk neighbors command, 223 show appletalk route command, 220 show...

Set and clear Commands

The keyword set is used with one or more commands and parameters to create, enable, disable, or modify a component, item, or variable within a switch's anatomy or configuration. For instance, the set cdp enable 3 1 command enables CDP on module 3 port 1 of a Catalyst switch. The set interface sc0 10 command configures the system console interface of a Catalyst switch to be a member of VLAN number 10. The set ip route destination netmask gateway command adds an entry to the switch's IP routing...

Show appletalk arp

The show appletalk arp command displays all the entries of the AppleTalk ARP (Address Resolution Protocol) cache. Example 7-6 displays a sample output of this command. Notice that each ARP entry comprises an AppleTalk address, age, type, hardware address, encapsulation (frame type), and the router interface through which the address was learned. Example 7-6 show appletalk arp Command Output

Show appletalk interface

This command will display AppleTalk information about all those interfaces that have AppleTalk enabled on them. However, if you specify the interface type and number along with the show appletalk interface command, then the output will be limited to only the specified interface. Example 7-2 shows a sample output of this command. Example 7-2 show appletalk interface Command Output A_StubR show appletalk interface ethernet 0 Ethernet0 is up, line protocol is up AppleTalk cable range is 1010-1019...

Show appletalk route

The show appletalk route command displays the AppleTalk routing table (see Example 7-3). The routing table displayed in Example 7-3 was obtained from a router called A_BackR connected to a network similar to the one shown in Figure 7-1. If you specify a network number with this command, only the routing table entry corresponding to that network will be displayed. If you specify an interface type and number after the show appletalk route command, only those networks that can be reached through...

Show appletalk traffic

This command provides a comprehensive set of statistics about AppleTalk traffic. The output is carefully organized into sections that allow you to grasp the activity and errors encountered by different members of the protocol suite (see Example 7-9). The show appletalk traffic command can be used as a monitoring, troubleshooting, or network baselining tool. Example 7-9 show appletalk traffic Command Output 51 total, 0 checksum errors, 0 bad hop count 51 local destination, 0 access denied, 0...

Show appletalk zone

The show appletalk zone command displays the contents of the zone information table (ZIT). Each zone is displayed along with the cable range(s) that fall within that zone. If you specify a zone name along with this command, then only the specified zone and the corresponding cable range(s) will be displayed (of course, if it is in the ZIT). Example 7-4 displays a sample output of the show appletalk zone command. Notice that in this instance the zone called AZone includes cable ranges 1010-1019...

Show bridge [bridgenumber

The show bridge command displays the contents of your router's bridge forwarding database for all the bridge groups defined (see Example 9-4). If you specify a bridge number, then of course the output will show only the information pertaining to the bridge group specified. Example 9-4 A Sample Output for the show bridge Command Total of 300 station blocks, 295 free Codes P - permanent, S - self Example 9-4 A Sample Output for the show bridge Command (Continued)

Show buffers Command

The show buffers command displays information (statistics) on buffer elements, public buffer pools, and interface buffer pools. Buffer elements are small data structures that are used for internal operating system queues or when a buffer must be associated with more than one queue. The public buffer pools are presented in the second section of the show buffers output and each buffer size (small, middle, and so on) is presented with its own statistics. The last section of the show buffers...

Show framerelay lmi [interface

This command displays LMI statistics about the interface under investigation. If you do not use the interface parameter, this information will be displayed for each and every Frame Relay interface (see Example 10-3). Example 10-3 A Sample Output of the show frame-relay lmi Command LMI Statistics for interface Serial1 The first line of this command's output tells you of the role of the router's serial interface (DTE UNI or NNI) and the LMI type it is configured for (UNI is the acronym for User...

Show framerelay map

This command displays the following information about each of the Frame Relay interfaces (see Example 10-4) The status of the interface (up, down, administratively down). The destination Layer 3 address (IP address). However, in the case of a point-to-point connection, the destination is identified with the phrase point-to-point dlci. The DLCI number in decimal, hexadecimal, and facility format. Whether the mapping is static or dynamic. In the case of a point-to-point connection, neither static...

Show framerelay pvc

The show frame-relay pvc command lists all of the PVCs that the router is aware of on all of its Frame Relay interfaces (and subinterfaces), along with their status, creation time, last status change time, and statistics regarding the sent received packets bytes and the congestion notification flags (see Example l0-5). Example 10-5 A Sample Output of the show frame-relay pvc Command PVC Statistics for interface Serial0 (Frame Relay DTE) LOCAL, PVC STATUS ACTIVE, INTERFACE Serial0 23, last time...

Show ip Commands

This section covers various show commands and explains their purpose and output. The following commands are covered This command lists a summary of an interface's IP information and status. Example 5-1 displays a sample output of the show ip interface ethernet 0 command. Example 5-1 show ip interface ethernet 0 Command Output A_StubR show ip interfaces ethernet 0 Ethernet0 is up, line protocol is up Broadcast address is 255.255.255.255 Directed broadcast forwarding is enabled IP fast switching...

Show ip protocols

This command displays the parameters and current state of the active routing protocol(s) (see Example 5-5). When troubleshooting IP routing cases, this command is often used to see which routing protocols are active, what their AS-number(s) or process-id(s) are, which networks they are configured for, if they are redistributing any routing information, and if there are any filters active for the routing protocols. Example 5-5 show ip protocols Command Output Sending updates every 90 seconds,...

Show ipx nlsp

NetWare Link Services Protocol (NLSP) is a link state routing protocol you may use for IPX routing. This protocol may be activated with or without a process tag. A process tag is useful in cases where you must run multiple copies of the NLSP process on the same router. The show ipx nlsp process-tag command must be used with one of the following parameters database, neighbors, or spf-log (see Example 6-7). This command is a specialized command that assists you in obtaining information about the...

Show ipx servers

The show ipx servers command displays the content of the local router's SAP table (see Example 6-5). The local router's SAP table contains a list of IPX servers learned through received SAPs, or those servers that the local router is statically configured to advertise. When you execute the show ipx servers command, the entries corresponding to those servers that the local router is statically configured to advertise appear with an S in front of them. The entries learned through NLSP have N, and...

Show ipx traffic

The output of this command is organized into several sections. The first section informs you of the total number of packets received along with a short report including the number of error conditions detected on those packets. Next, the number of broadcasts sent and received, and the number of packets sent, forwarded, and dropped (due to encapsulation failure or no route conditions) are reported. The sections following provide statistics on SAP, RIP, IPX Echo, Watchdog, queue lengths, and any...

Show logging Command

To display the state of syslog error and event logging, including host addresses, which type of logging (destination) is enabled, and other logging statistics, use the show logging (privileged EXEC) command. This command also displays the messages that are logged in the buffer. Example 4-2 displays sample output of the show logging command. Example 4-2 The show logging Command Router show logging Syslog logging enabled Monitor logging level debugging, 13 messages logged. Trap logging level...

Show processes Command

The show processes exec command displays your router's CPU utilization and a list of active processes along with their corresponding process ID, priority, scheduler test (status), CPU time used, number of times invoked, and so on. This command is also very useful when you are evaluating your router's performance and CPU utilization. A sample output of the show processes command is shown in Example 4-10. As you can see, the first line of the output shows the CPU utilization for the last five...

Show span [vlannumber

This command first appeared in Cisco IOS Release 10.3 and it shows the Spanning-Tree Protocol information known to the router (see Example 9-3). The first part of this command's output shows the type of Spanning-Tree Protocol in use, the bridge ID (priority and address) of the local device (the router), the ID of the root device, and the timer parameters of the spanning tree. Next, the interfaces that participate in the spanning tree (associated to the VLAN number typed in) are listed. For each...

Show stacks Command

Show stacks is an exec command that is commonly used to diagnose system crash situations. The first section of this command's output displays stack utilization of processes and interrupt routines, and the reason for the last system reboot. When a system crash happens, failure type, failure program counter (PC), address (operand address), and a stack trace are saved by the ROM Monitor. The show stacks command displays the data saved by the ROM Monitor. The stack trace is displayed in the second...

Show version Command

This command is one of the most popular fact-gathering commands. Example 4-6 displays a sample of the show version command executed at a Cisco 2514 router. Example 4-6 show version Command Output Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-JS-L), Version 11.3(6), RELEASE SOFTWARE (fc1) Copyright 1986-1998 by cisco Systems, Inc. Compiled Tue 06-Oct-98 22 17 by kpma Image text-base 0X03048CF4, data-base 0x00001000 ROM System Bootstrap, Version 5.2(8a), RELEASE...

Show vlans

The show vlans command lists all the VLANs configured on a router. Example 9-2 shows a sample output of this command. For each VLAN, the corresponding subinterface and its configured addresses (for instance, IP and IPX) are displayed. For each protocol configured on a subinterface, this command also shows the number of packets sent and received. Example 9-2 A Sample Output for the show vlans Command Virtual LAN ID 1 (Inter Switch Link Encapsulation) Virtual LAN ID 2 (Inter Switch Link...

Specific IPX Symptoms Causes and Recommended Actions

The remainder of this section covers specific symptoms, their possible cause(s), and recommended corrective action(s). Symptom Client cannot make connection to the local LAN's server. Possible Cause 1 Client or server is misconfigured. Action Check the network adapter card and its device driver (on both the client and the server), and the net.cfg file (on the client). Possible Cause 2 Encapsulation is mismatched. Action Verify that the encapsulation specified on the client and the server are...

Switching in 4000 3000 and 2500 Series Routers

On the 4000, 3000, and 2500 series routers, unlike the high-end routers discussed previously, the options are process switching and fast switching only (see Figure 4-3). Fast switching, a term often used when referring to route caching in shared memory, is enabled by default on all interfaces for all supported protocols. Figure 4-3 Routing and Switching in 4000, 3000, and 2500 Routers Cisco 4000, 3000, 2500 Switching Types Figure 4-3 Routing and Switching in 4000, 3000, and 2500 Routers Cisco...

Switching in 7000 Series Routers

The 7000 series routers, similar to other Cisco routers, have a fast switching option that is enabled by default. Fast switching is performed using a Fast Switch Cache in the Route Processor. Two major components that participate in the routing and switching operations are RP (Route Processor) and SSP (Silicon Switch Processor). The early models of the 7000 series had RP and SP (Switch Processor). The SP (in the earlier models) only had an Autonomous Switch Cache. The SSP was introduced later...

Switching in 7500 Series Routers

To enhance the performance and efficiency of its high-end routers, Cisco Systems made some major improvements in the 7500 series routers The internal bus of the 7500 series router (CyBus) operates at1 Gbps, which is about twice as fast as the 7000 router's CxBus. Instead of having two separate components for routing and switching (SSP and RP) as in 7000 routers, the 7500 router is equipped with one component called the Route Switch Processor (which eliminates the slow 153 Mbps system bus...

Switch Router Configuration Consistency

There are five default VLANs preconfigured on a Catalyst 5000 switch for different media types. Table 9-1 shows these VLANs along with their associated MTU, ISL VLAN ID, and 802.10 Security Association Identifier (SAID). Numbers 1 though 1000 may be used for the VLANs created on a Catalyst 5000 family switch. You are encouraged to leave VLAN number 1 for management and troubleshooting and use VLANs 2 through 1000 for user (traffic) VLANs. When you connect a router and a switch via a trunk...