Your purchase, acceptance or use of the Software will constitute your acceptance of such terms. Your purchase, acceptance or use of the Software will constitute your acceptance of such end user licenses.
Cisco Certified Internetworking Expert (CCIE)
Always check the Cisco website for the most current information (www.cisco.com). Cisco has been adding new sites for the CCIE lab lately; For the most current information, it is best to consult the Cisco website.
Cisco’s Network Design Certifications
Cisco Certified Design Associate (CCDA)
What Does This Book Cover?
To really nail your skills, read each question carefully and, if possible, go through the hands-on labs in some of the chapters.
Where Do You Take the Exam?
Remember to read the choices carefully because "close doesn't cut it." If you get commands in the wrong order or forget a measly character, you will get the question wrong. When answering multiple-choice questions that you are not sure about, use a process of elimination to get rid of the obviously wrong answers first.
How to Use This Book
Appendix B contains all the commands used in the book, including explanations for each command. To learn all of the material covered in this book, you must apply yourself regularly and with discipline.
What’s on the CD?
Be sure and read the key list of terms and commands in this chapter list at the end of each chapter.
The EdgeTest for Cisco Support Test Preparation Software
Electronic Flashcards for PC and Palm Devices
If you work hard, you will be surprised at how quickly you learn this material. This will be extremely useful for readers who travel and don't want to carry a book with them, as well as for readers who find it more comfortable to read from their computer.
Boson Software Utilities
CCNA Virtual Lab AVI Demo Files
How to Contact the Authors
LMI B. Cisco
CHAP B. PPP
What command(s) can be issued in Windows 98 to provide IP interface information. Select all that apply.) See Chapter 6.
ANSI
IETF B. ITU-T
IGRP B. BGP
Which of the following is information that will be requested when opening a TAC case. Which of the following are valid troubleshooting targets when troubleshooting Novell NetWare (IPX) networks.
SDLC B. PPP
Last input never, output never, output never hangs Last clear of "show interface" counters never Queuing strategy: fifo.
EARL B. DUKE
TCP B. Ethernet
For further explanation of the reasons for using a troubleshooting method, see Chapter 1. All of these devices are used to test physical media. For additional information on physical media test equipment, see Chapter 3. These protocols use the D channel for signaling information.
Chapter
Troubleshooting Methodology
TOPICS COVERED IN THIS CHAPTER INCLUDE
Define the Problem
As you can see, the user's problem is really vague; if you want to solve the problem soon, you need more information. Once you have enough information to define the problem, you must create a problem statement that is a specific, concise, and accurate description of the problem to be solved.
Gather Facts
To be more specific, it is important to obtain as much information as possible to actually define the problem while you are in the problem definition phase of the problem solving model. All of this information can be used to guide you to the actual problem and create the problem statement.
Identify Symptoms
It's up to you as a network engineer or administrator to fix the problem, which means you may have to find the information yourself. Without a proper and specific definition of what the problem is, it will be much more difficult to isolate and solve.
Reproduce the Problem
Understand the Timeline
Determine the Scope of a Problem
If this test fails, the only thing you can try is to FTP to another machine in the user's segment. You can see that the user can FTP to machines on the same network, but cannot FTP to any device on the Campus B network.
Using Baseline Information
- Consider Possibilities
- and 5: Create and Implement the Action Plan
- Iterate as Needed
- Document the Changes
The most important thing is to be able to revert to the original configuration if unforeseen problems arise as a result of the change. Once all the changes from the action plan are implemented and the results are observed, you can verify if the action plan solved the problem.
Key Terms
What is the main purpose of the Define Problem step in the problem solving model. Which other step of the problem solving model is most similar to the Implement Action Plan step.
Protocol Attributes
We briefly review the seven layers of the OSI model and then discuss how they communicate with each other. Once the ones and zeros reach the physical layer of the destination system, the information is sent to layer 2.
Connection-Oriented Protocols
If, for some reason, the destination system cannot fulfill any of the requests sent by the originating system, it responds with a connection refusal. The destination system sends control information that informs the originating system what should happen next.
Sequenced Data Transfer
Flow Control
Error Control
As you can see, both systems communicate a lot, apart from exchanging data. From the connection request to the completion confirmation, each exchange is accompanied by control information that keeps the data transfer reliable and error-free.
Connectionless Protocols
Some of the transport layer's responsibilities are session establishment, flow and error control, and session teardown. This section discusses seven different protocols used within Layer 3 of the OSI model.
Internet Protocol (IP)
The following sections begin discussions of protocols that are specific to the Network and Data-Link layers, respectively. Some are routing protocols and others are protocols that are driven by routing protocols.
IP Packet Structure
The position is measured from the beginning of the datagram and marked in 64-bit increments. Because this is just a review, we'll leave IP addressing at this point and move on to some of the other protocols used within the IP suite.
Transport Control Protocol (TCP)
The fifth layer of the TCP header begins with the Checksum Parameter, which also occupies 16 bits. The packet is divided into nine fields, and zeros are used to pad the packet to the full 24 bytes.
Interior Gateway Routing Protocol (IGRP)
IGRP Features and Operation
External routes learned via IGRP from another AS number and providing information used by the router to set the gateway of last resort. The gateway of last resort is the path a packet takes if no specific route is found on the router.
Routing Stability
When a route's associated metric increases by a factor of 1.1, IGRP issues a reverse poison update that removes the affected route from a router's routing table and places it in hold-down. This enhanced version uses the same distance vector information as IGRP, but with a different algorithm.
Route Tagging
Neighbor Relationships
When the topology database is updated, the original router advertises its entire table to all the new neighbors. Neighboring routers acknowledge receipt of the routing information from the originating router by sending back an ACK packet.
Route Calculation and Updates
On the other hand, if the connection between Router A and Router C becomes congested, both routers must calculate a new route metric.
Topology and Route State Information
The path with the best metric (lower is better) is chosen as the primary path. EIGRP uses the same vector information as IGRP: bandwidth, delay, reliability, load, and MTU.
Updates and Changes
Configuring reliability, load, and MTU can cause the topology table to be calculated more frequently.
Open Shortest Path First (OSPF)
Area Identification The OSPF area number and link information must be the same for a peering session to be established. Stub Zone Flag This is a special zone—two routers must share the same stub information.
OSPF Packet Structure
Each AS also has an ID included in the packet, so not only is the packet's source router identified, but so is the AS.
BGP (Border Gateway Protocol)
BGP Packet Structure
NetWare uses the top five layers of the OSI model to run a network operating system. Since the top five layers are proprietary to Novell, they must use special mappings to use the lower layers of the OSI model.
IPX Packet Structure
The packet type indicates which of the upper layer protocols should receive the PDU after it has been processed by Layer 4. This is followed by the Source node, a 48-bit field containing the MAC address of the source host.
AppleTalk Protocols
The selector queries the router for available zones and presents the list of available zones to the user. The user's MAC issues an NBP request, identifying the requested resource type and area.
AppleTalk Addressing
If the network number for the temporary address falls between the segment's cable range, the address is retained. Once the node finds an unused network number and a combination of node numbers, that becomes its final node address.
Datagram Delivery Protocol (DDP)
If the node starts up for the first time, it randomly chooses a network number between 65,280 and 65,534. In both cases, the node uses AARP to verify that the selected temporary address is in use.
Routing Table Maintenance Protocol
Ethernet serves both the physical layer and the data link layer, while IEEE 802.3 is more concerned with the physical layer and how it communicates with the data link layer. Ethernet defines the field as a Type field, while IEEE 802.3 defines it as a Length field.
Token Ring/IEEE 802.5
Tokens
When the source is reached, the frame is removed and a new token is generated and sent out on the ring.
Fault Recovery
Token Frame Format
Fiber Distributed Data Interface (FDDI)
FDDI Specifications
The protocol encodes and decodes the data, before and after transmission over the physical media. This specification is concerned with the way FDDI works as a Layer 2 technology, the physical addresses and the way the data is presented to the Physical layer.
Frame Structure
The data field is followed by the frame check sequence, which calculates the CRC for the received frame. As with Token Ring/IEEE 802.5, the frame status indicates whether the frame has been copied or stored by any station on the ring.
Point-to-Point Protocol (PPP)
An incoming channel is shared between the secondary stations and has a single connection to the primary station. The secondary address is used because all communications originate from or are received by the primary node; so there is no need to specify the address within the frame.
SDLC Derivatives
After the sending sequence number, one or two bits are used to determine the frame type. Now that we have discussed frame structure, we need to discuss the three different types of frame.
Frame Relay
The frame used in Frame Relay is similar to the frame used in X.25 except for two major differences. The first difference is that Frame Relay leaves flow and error control to higher-layer protocols.
Integrated Services Digital Network (ISDN)
- ATM B. UDP
- PPP D. Novell IPX
- TCP D. SMTP
- ARPA B. SAP
If set to one byte, this is the last field within the Address field. Network Layer Protocols We have discussed IP and other members of the IP suite such as ICMP and TCP.
Generic
Troubleshooting Tools
It is important to recognize that many tools can be used in a proactive method such as monitoring. Some tools are part of the TCP/IP protocol stack, others are systems that capture frames and decode them with software, and still others are used to test physical media.
Multimeters and Cable Testers
It's amazing how many network problems can actually be solved by testing and then fixing wiring problems. It is important to realize that not all cable testers provide all of this information.
Time Domain Reflectors (TDRs) and Optical TDRs (OTDRs)
Digital Interface Testing Tools
While monitoring line conditions is an option with these types of tools, they are not capable of analyzing protocol information on a line. There are basically two types of software used to troubleshoot network problems: network monitoring and network analysis.
Network Monitors
Network Analyzers
EtherPeek
You can tell it is a Layer 2 packet because there is no IP or other Layer 3 header decoding. You can see all flow control information as part of the TCP packet.
LANWatch
You can move between marked packages using the toggle options available from the Edit menu. You can see the active filter displayed in the Filters window on the LANWatch front screen.
CiscoWorks 2000
Resource Manager Essentials
Because SNMP is not the focus of this book, we do not spend much time explaining its intricacies. It does all this via SNMP, with a little help from other protocols, such as TFTP for file transfer, although the command is issued via SNMP.
CWSI
Tracking is used to help move user information from one VLAN to another or to provide consistent VLAN assignment if the physical cable is moved from one port to another on the switch. Because these tools were developed for Cisco devices, the MIB objects needed to manage the devices are preprogrammed into the software.
NetSys
- TDR B. OTDR
- TDR B. Cable tester
- OTDR B. Cable tester
- SNA B. SAP
- SNA, SNMP, PING, TRACEROUTE, DNS
- TACACS+
Authentication is used to verify that the user is who they say they are and that they are allowed to log in to the device. What tools can be used to check fiber optic cable length, cable attenuation, or the approximate location of a cable fault.
Cisco’s Diagnostic Commands
This chapter discusses Cisco diagnostic command output and Cisco-specific routing and switching procedures. This section is devoted to a discussion of the processes that take place on Cisco routers.
The Routing Process
Routing protocols are used to enable routers to calculate, learn, and advertise routing table information. Metrics are calculated by the routing protocol to determine the cost of arriving at the destination address.
The Switching Process
Assuming the packet is not intended for the router, it is sent back to Layer 2 to be encapsulated (step 3). With the frame header created, the packet is encapsulated and sent to the next hop (step 4).
Cisco 7000 Series Router Architecture
