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....

Acknowledgments

I did not have the pleasure of getting to know or communicating with all of the individuals that have put their valuable time and effort into this book, but I would like to use this opportunity to sincerely thank each and every one of them. Among those who I did directly work with was Brett Bartow, whose patience, professionalism, and understanding I will never forget. Brett played a key role in the development of this book from the very beginning. Thanks to Andrew Cupp for his sharp eyes and...

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...

Apple Talk show Commands

Cisco IOS offers several show appletalk commands. Some of these commands display configuration information (default and configured), some present statistics, and others display dynamically learned information. Example 7-1 displays the show appletalk options that are provided by the help feature of Cisco IOS. The following important show appletalk commands are listed and briefly explained in this section. show appletalk access-lists show appletalk adjacent-routes Example 7-1 show appletalk...

Applying Cisco Troubleshooting Tools

This chapter introduces some powerful troubleshooting tools that are built into the Cisco IOS. As with other tools, it is important that you identify when to use them and what information they reveal. Because some of these tools have an impact on the way routers operate and may impede the routers' utmost performance, it is essential to use them with care. To better understand the output of these commands, and to recognize what router internal operations they affect, this chapter discusses...

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...

Browser Issues in Microsoft Products

In networks with hosts running Microsoft Windows NT 95, users often look for servers offering file shares and printer shares through the Network Neighborhood applet. The list of servers offering these services is maintained and distributed through the collective effort of all devices running the Browser service. The Browser service is broadcast-based for the most part and its operation is very smooth in one segment. However, many Windows NT domains span more than one segment, and for 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 400030002500

In Cisco 4000 3000 2500 routers, because there is no SP, SSP, or RSP, buffers reside on the shared memory. Packets enter into an interface (hardware buffer), and they are sent directly to the shared memory. In shared memory, a packet is kept in the input queue corresponding to the ingress interface. Next, an output interface for the packet is possibly selected (perhaps after the process switching or fast switching task completes). Then the packet is held in the output queue of the egress...

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...

Call Rejection May Be Caused by Call Screening

On each BRI interface, you may enter two numbers (using the ISDN answerl and ISDN answer2 interface configuration commands) to force the router to answer an incoming call on a particular BRI interface, but only if the number dialed by the other party matches the numbers you specify. Naturally, this technique will be effective only if the switch hands that information over to your router. When troubleshooting ISDN call setup failures, keep in mind that this BRI interface configuration command...

Case 1 Users Report that the Connection to Their Designated Local Switch is Not Working

In this case, users report that the connection between their devices (workstations) and their designated local switch is not working. It is very possible that the switch has lost power, perhaps due to failure of its power supply or a blown fuse. If the fuse is blown, refer to the user guide for your LAN switch for information on replacing the fuse. If the power supply is working (the LED is green), you must check the system LED (on the supervisor), the appropriate module status LED, and,...

Case 3 Switch Cannot Be Accessed from Remote Devices

This case is usually due to one or some of the following problems Invalid or unassigned IP address on the SCO. Invalid subnet mask on the SCO, no default gateway, inappropriate static route(s). Invalid VLAN number assigned to the SCO. The IP address on the switch's SCO must be a unique IP address from a valid IP subnet. Use the show interface command to verify SCO's IP address, mask, and VLAN number. Correct these parameters using the set interface sc0 command. Also, check the switch's routing...

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...

Catalyst 5000 Switch Diagnostic Tools show Commands

You are expected to be familiar with the Catalyst switch's set, clear, and show commands. This section will focus on reviewing those commands (mostly show commands) that are essential for diagnostics and troubleshooting. First, though, it is important to emphasize the value of the online help utility of Catalyst switch's IOS. One of the great features of the Catalyst switch's IOS help utility is that if you seek help or make a mistake, it provides you with the full syntax of the command you are...

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 Software Library

Cisco describes the Software Library as a full-service one-stop-shopping location for all phases of Cisco software product lifecycles. You can obtain upgrades and learn more about Cisco's software products, including Cisco IOS software (for routers, switches, or gateway platforms), network management and security applications for workstation servers, and internetworking protocol sites for host systems all from one place. In addition to offering major upgrades and maintenance releases of Cisco...

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...

CCO Troubleshooting Engine

The Troubleshooting Engine link on the Cisco Technical Assistance Center (TAC) page takes you to the Troubleshooting Engine page. The Troubleshooting Engine helps you solve common problems involving hardware, configuration, and performance. However, to deal with complex issues such as incompatibilities or software defects, you must go to the Open Forum page (discussed later in this chapter). The Troubleshooting Engine presents you with a list of various topics (such as IP routing protocols)....

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...

Identifying Troubleshooting Targets

Do I Know This Already Quiz 49 Foundation Topics 52 Understanding Data Link Troubleshooting Targets 52 Troubleshooting Physical and Data Link Protocol Characteristics 52 The show interfaces ethernet n Command 55 The show interfaces tokenring n Command 62 The show controller token Command Section 1 65 The show controller token Command Section 2 66 The show controller token Command Section 3 66 Token Ring Soft Errors 67 Understanding Protocol Connection Troubleshooting Targets 78 The show ip arp...

Applying Cisco Troubleshooting Tools 101

Do I Know This Already Quiz 101 Foundation Topics 105 System Impact of Cisco Troubleshooting Tools 105 Cisco Routers' Routing Processes and Switching Processes 105 Switching in 7000, 7500, 4000, 3000, and 2500 Series Routers 107 Switching in 7000 Series Routers 108 Switching in 7500 Series Routers 110 Netflow Switching 112 Switching in 4000, 3000, and 2500 Series Routers 112 Process-Switched Packets 114 Handling the Cisco IOS Debug Troubleshooting Tool 115 Using an Access List with Debug 116...

Diagnosing and Correcting Novell Networking Problems 189

Do I Know This Already Quiz 189 Cisco IOS Troubleshooting Commands and Tools for IPX 191 Ping for IPX 191 The show ipx Commands 191 The Debug IPX Commands 198 Problem Isolation in IPX Networks 201 IPX Connectivity Symptoms, Possible Causes, and Suggested Actions 202 The Issue of Frame Type in IPX Networks 203 The gns-response-delay Issue 203 Specific IPX Symptoms, Causes, and Recommended Actions 204

Diagnosing and Correcting Apple Talk Problems 215

Do I Know This Already Quiz 215 AppleTalk Configuration and Troubleshooting Checklist 217 The ping appletalk and test appletalk Commands 217 AppleTalk show Commands 218 show appletalk interface 219 show appletalk route 220 show appletalk zone 220 show appletalk access-lists 221 show appletalk adjacent-routes 221 show appletalk arp 222 show appletalk globals 222 show appletalk name-cache 223 show appletalk neighbors 223 show appletalk traffic 223 debug apple Commands 224 debug apple arp 225...

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...

Troubleshooting VLANS on Routers and Switches 285

Do I Know This Already Quiz 286 Troubleshooting Cisco IOS Configuration 289 VLAN Design Issues for Troubleshooting 291 Switch Router Configuration Consistency 291 Router VLAN Diagnostic Tools show Commands 293 show vlans 293 show span vlan-number 294 show bridge bridge-number 295 show interface fastethernet 0 296 Router VLAN Diagnostic Tools debug Commands 297 debug vlan packets 297 debug span tree and debug span events 298 Problem Isolation in Router Switch VLAN Networks 299

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...

Cisco Works

CiscoWorks is Cisco Systems' network management software. This software is based on Simple Network Management Protocol and it is for managing networks with one integrated platform. CiscoWorks provides services that have both operations and management value. Network managers can monitor routers (down to port activity), observe traffic patterns, modify configurations, observe and report inventory, capture data (for accounting purposes), and observe security settings all from their one central...

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...

Consider the Possibilities

The main focus here is to use your knowledge of the network, devices, and software releases along with the gathered facts to formally eliminate improbable possibilities and set a boundary for the problem area. It is quite usual to end up with a few hypotheses surrounding a small portion of the network. Hence, you will have a better focus (on a few devices as opposed to the whole network), and a narrowed set of possibilities. One last step you are supposed to take is to order the remaining...

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...

Core Dumps

The full copy of memory image is called a core dump. This image can be useful for determining the cause of a crash. Core dumps are usually submitted to Cisco support engineers, who are specialized in analyzing the memory image (using source codes, memory maps, etc). The core dump can transfer the binary image file using TFTP, FTP, or RCP protocols (see Figure 4-7). You must remember that performing a core dump disrupts regular network operation. write core exception dump ip-address write core...

Create an Action Plan

For each possibility (among those that are remaining), you must come up with one or more actions that will need to be implemented in order to solve the problem(s). It is crucial that discrete actions do not get mixed they should remain separate. Often people change too many things at once. If they fix the problem, they will not be able to tell what the real problem was and, hence, which action corrected it. Furthermore, it is possible that a change will be implemented that is not necessary...

D

Depending on the operations performed on a particular interface, fast switching might have to be disabled manually or it may get disabled automatically by the IOS while that operation or configuration is in effect (this is IOS dependent). For instance, say you enter the command that applies a priority queue to an interface depending on the IOS version, fast switching on that interface might be disabled by the IOS automatically, or the IOS might prompt you to disable fast switching before it...

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 errors

The debug apple errors command is used to display AppleTalk error messages so that you can identify the cause of your network problem. These messages may be generated for many reasons. AppleTalk problems are usually due to mismatching cable range network number(s), zone name(s), ordering of zone names (Primary, Secondary, and so on), and mixture of AppleTalk Phase I and Phase II among neighbors. The error messages displayed by the debug apple error command include Net information mismatch,...

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 ipxwan

IPXWAN (defined in RFC 1634) allows a router that is running IPX routing to connect via a serial link to another router that is also routing IPX and using IPXWAN. IPXWAN is a connection startup protocol, and once a connection has been established, it is virtually overhead-free. The IPXWAN protocol can be used over PPP or over HDLC (in case of HDLC, both routers must be Cisco routers). The ipx ipxwan interface configuration command (with the appropriate parameters) is used to enable IPXWAN on a...

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 Notes

Debug is a troubleshooting command 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 lets you discover significant facts about the working and faulty software and or hardware components. debug is available from the privileged exec mode (of Cisco IOS). debug is treated as a very high priority task. debug can consume a significant amount of resources. The router is forced to...

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...

Define the Problem

Defining the problem is a very straightforward task. Problem definition is a clear statement (with few, preferably no ambiguous terms) of the problem in terms of the associated symptoms and possible causes. It is often useful to make a reference (or comparison) to the normal and expected behavior. If you have your network baseline information, refer to it in your problem statement. Along with identifying the observed symptoms, the problem definition should also mention what faults and or...

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 Catalyst Problems

To diagnose and correct Catalyst switch problems, you need to be familiar with the function and operation of the switches, their IOS's commands, and the troubleshooting tools and commands that assist identifying the source of the reported problems. Proper installation, cabling, and configuration of interfaces, ports, VLANs (Virtual LANs), trunks, Spanning Tree, and VTP (VLAN Trunking Protocol) are the basic requirements of a working switched internetwork. To monitor and support switched...

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...

Diagnosing and Correcting Novell Networking Problems

To design and configure IPX networks with Novell servers, you need to be familiar with the IPX SPX protocol stack, understand some or all of the IPX routing protocols, be acquainted with the operation of Novell servers (and SAP), and have knowledge of IPX traffic management. To support IPX networks, you'll need to know all of this plus the necessary troubleshooting tools and commands, and have knowledge of common errors and poor procedures. This chapter lists and briefly explains a set of Cisco...

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....

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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,...

Embedded RMON Agent and Switch Probe

The Catalyst 5000 software includes an integrated RMON agent.The structure of the remote network monitoring MIB (Management Information Base), as outlined in RFC 1757, defines nine groups that objects are arranged into. Four of those groups that are supported by the Catalyst 5000 embedded RMON agent are the (Ethernet) statistics group, the (Ethernet) history group, the alarms group, and the event group. The (Ethernet) statistics group contains statistics measured for each monitored Ethernet...

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...

Escalation to Cisco Service and Support

Cisco Systems customer engineers that are members of the Cisco TAC are yet another resource available to you worldwide. There may be a time when the effort to solve your internetwork problems using the variety of tools and resources surveyed in this chapter does not lead you to a solution. This assistance may be obtained based on your warranty or contract or on a billable basis. You may contact Cisco TAC via telephone, facsimile, e-mail, or online from the Case Open page on CCO. To open a case...

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...

Foundation Topics System Impact of Cisco Troubleshooting Tools

After completing the problem definition step, your next step (following the systematic troubleshooting process) is to start gathering detailed facts about the behavior of the devices and protocols of the production network. This task usually entails using several IOS troubleshooting tools and commands. Despite their importance in terms of the valuable information they provide, these tools inevitably utilize some processing cycles and memory of the router. Furthermore, they may disable or at...

Foundation Topics Understanding Data Link Troubleshooting Targets

All networking layers, except the physical layer, rely on the correct operation of the data link (control). If there are faults at this layer, problems such as application fails, cannot make connection, network is slow, data is distorted, and so on will be reported. The data link layer connects devices, which are subsequently called adjacent devices. For adjacent devices to communicate, they must send and receive error-free data with a reasonable delay (latency). When troubleshooting the data...

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...

Gather the Facts

You gather facts from different sources. You have to talk to network administrators, other support engineers, managers, and anybody else that can provide relevant key information. In many cases, a change that is believed to have no effect on other traffic activities is not reported (even when you explicitly ask) you may end up finding such changes for yourself in this step. The fact gathering step may involve some basic testing tools (such as ping, trace, and so on) or some more involved ones...

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...

Implement Your Action Plan

At this point you take the most promising hypothesis and implement the corresponding action plan that you believe will correct the problem(s). This plan may be composed of only one or more than one action. If the latter case is true, it is important to make sure that every one of the (individual) actions is required to be implemented at once. Otherwise, you should, without a doubt, separate the actions and implement them one at the time. For example, your plan might be to start an OSPF process...

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...

IPX Connectivity Symptoms Possible Causes and Suggested Actions

In order to be effective in troubleshooting, in addition to possessing relevant skills and background knowledge, it is also helpful to be familiar with the scenarios that have been dealt with in the past. Some of these cases stem from the special features of certain Cisco IOS versions (e.g. gns-response-delay), designed to accommodate certain products, protocols, or applications behavior. Other cases are merely those that are worth keeping in mind simply due to their past frequency of...

Issues Regarding Redistribution between IP Routing Protocols

Two different routing protocols active on the same router do not automatically learn any routing information from each other (in general) and naturally do not advertise the routing entries of the other protocol. When you need the routing information available in one routing protocol to be imported into another routing protocol, you need to configure redistribution. For instance, if you want a RIP process to take entries from an IGRP 100 process, you need to enter the redistribute igrp 100...

Iterate the Process

Assuming that even after implementing your previous action plans the problems still persist, you need to consider the next hypothesis and go about implementing its corresponding actions. If you have not spelled out the actions of the next hypothesis, of course, you now have to do that. Inevitably, there will be times that you remain with no possibility or hypothesis in hand while your network problems still exist. What do you do then The answer is that you have to think of more possibilities....

Logging Options

Table 4-11 shows logging options and their corresponding commands. Table 4-11 Logging Options and Their Corresponding Commands Table 4-11 shows logging options and their corresponding commands. Table 4-11 Logging Options and Their Corresponding Commands This command turns console logging on and specifies the level of logging to be directed to the console. (The default setting is The no logging console command disables console logging. Table 4-11 Logging Options and Their Corresponding Commands...

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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...