A

AAA (authentication, authorization, accounting), configuring, 557-559 AAL (ATM Abstraction Layer), 223 aborted connections, 286 ABR (available bit rate), 232 ABRs (area border routers), 379 summarization, configuring, 384-385 access layer, hierarchical routing model, 35 access lists, 574-575 bridging access lists, 161-162 firewall implementations, 562 IPX, 574 SAP, 574-575 Windows NT, 576 access methods CSMA CD, 112 WLANs, 128 accessing devices, 83 with auxiliary port, 83 with console, 83 with...

A a a a a n

The IEEE 802.11b standard uses the 2.4 GHz band of the Industrial, Scientific, and Medical (ISM) frequencies. The Federal Communication Commission (FCC) authorizes ISM frequencies for unlicensed use in the United States. The three ISM frequency bands are as follows IEEE 802.11, 802.11b, and 802.11g standards all use the 2.4 ISM band. The IEEE 802.11a standard uses the 5 GHz bands of the Unlicensed National Information Infrastructure (UNII) frequencies. The three UNII bands are as follows 5.15...

Aaa

AAA (triple A) provides a modular framework for configuring three security functions. The three functions are as follows Authentication Who is the user Authorization What resources can be accessed Accounting When was the device accessed, by whom, and what commands were used Authentication allows the identification of the user that is accessing the device. Authentication can include login and password dialogs, challenge and response, and encryption. Authorization specifies the level of access...

About the Contributing Author

Roy Spencer is a Cisco Certified Network Associate for WAN switching and a Certified Cisco Systems Instructor with over fifteen years experience in the education segment of the networking industry. He has worked as a course developer for Cisco Systems, Inc., 3Com Corporation, and Nortel Networks Limited. Roy has written and taught classes on ATM switch configuration, network management, router configuration, LAN switch configuration, SONET multiplexers, Ethernet, and TCP IP. He is currently...

Accessing Devices

Routers can be accessed and managed by the console through modem dial-up into the auxiliary port, through a virtual terminal (i.e., Telnet), through asynchronous interfaces, or through Simple Network Management Protocol (SNMP). When accessing router consoles, the terminal emulation is set as follows The console is configured as follows This port is usually connected to a modem for remote access as follows You can reach a configured router through a virtual terminal (i.e., Telnet). Virtual...

Address Family Identifier AFISet to a value of 2 for IP

IP Address This is the destination route it can be a network address, subnet, or host route. You use special route 0.0.0.0 for the default route. Metric The metric field is 32 bits in length. It contains a value between 1 and 15 inclusive, specifying the current metric for the destination. The metric is set to 16 to indicate that a destination is not reachable. Because RIP has a maximum hop count, it implements counting to infinity. For RIP, infinity is 16 hops. In the RIP message, no subnet...

Administrative Distance Configuration

To change the administrative distance for routing protocols, use the distance number command. The number value ranges from 0 to 255. For OSPF, separate distances are configured for external, intra-area, and internal routes. The command examples in Table 10-2 change the administrative distances of routing protocols to a number between 40 and 50. (Don't do this on a real internetwork ) Table 10-2 Use of the distance Command for Routing Protocols Static routes have a default administrative...

Aggregateaddress Command

The aggregate-address command advertises an aggregate (summary) network if any more-specific prefixes are present in the BGP table. A summary-only keyword suppresses advertisements of the more-specific prefixes. For example, if the BGP table has networks 100.100.4.0 24, 100.100.5.0 24, 100.100.6.0 24, and 100.100.7.0 24, you can configure it to advertise an aggregate network of 100.100.4.0 22 and suppress the more specific networks. The commands are as follows aggregate-address 100.100.4.0...

An Alternate Method

The dividing procedure described previously works, but it takes a lot of time. Another method is to remember the bit position values within a byte 128, 64, 32, 16, 8, 4, 2, 1, and play with the bits until the sum adds up to the desired number. Table 2-5 shows these binary numbers and their decimal value. To convert 26, you know that it is a number smaller than 128, 64, and 32, so those three bits are 0 000 . Now, you need to find a combination from 16, 8, 4, 2, and 1 that adds up to 26. This...

Answers to Quiz Questions

This appendix contains answers to the Q & A questions from each chapter. In each chapter, the Q & A questions repeat the Do I Know This Already questions for assessment purposes, so you will also find the answers to those questions here as well. (The Do I Know This Already questions are always the first questions in each chapter's Q & A.) For your convenience, the questions are repeated here with the answers, so you can also use this appendix as a study tool.

Application Layer OSI Layer

The application layer provides the user or operating system access to the network services. It interacts with software applications by identifying communication resources, determining network availability, and distributing information services. It also provides synchronization between the peer applications that reside on separate systems. Examples of application layer specifications are the following File Transfer Protocol (FTP) Simple Mail Transfer Protocol (SMTP) Simple Network Management...

AS Path Length Attribute

The AS Path is a well-known, mandatory attribute that contains a list of AS numbers in the path to the destination. Each AS prepends its own AS number to the AS Path. The AS Path describes all the autonomous systems that a packet must travel to reach the destination IP network it ensures that the path is loop free. When the AS Path attribute selects a path, the route with the least number of AS hops is preferred. In the case of a tie, other attributes, such as MED, decide. Example 9-9 shows the...

ATM Architecture

This section uses the ATM reference model to describe the general architecture of ATM. ATM was developed to meet the need to transport voice, data, and video across enterprise and service provider networks. ATM is a connection-oriented, cell switching, transport technology. ATM supports the ability to adapt to different bandwidths and QoS requirements. Figure 5-14 ATM Reference Model shows the various functions within the ATM architecture. The ATM reference model is divided into three areas...

ATM Cell Switching

The header of each cell contains addressing information consisting of a VPI and a VCI. The VPI VCI address pair is locally significant. For each interface in a switch, the VPI VCI uniquely identifies the cell as belonging to a particular connection. When a VC connection is established across a network, each switch involved in the connection creates an entry in its switching table that identifies the incoming VPI VCI and interface number for the connection. The switching table entry also...

ATM Connections

ATM is a connection-oriented technology. A connection is established between two or more ESs to permit communication. A connection between two end points is called point-to-point. A connection between a single originating end point and multiple destination end-points is called ATM uses the concept of virtual connections between ESs rather than physical links. ATM networks support a connection type known as a PVC, which is established manually from a source end-point to a destination end-point....

Atm Es Addresses

To support SVCs and PNNI routing of connections, switches and interfaces must be assigned a 20-byte ATM address. Each ES must have at least one ATM ES address (AESA). The AESA identifies the PNNI peer group, the switch ID, and the ES ID. When the originating end device sends a SVC connection request, it identifies the ATM address of the destination device. The following three types of addresses are used in private ATM networks Data Country Code (DCC) DCC addresses always start with a prefix of...

ATM Interface Configuration

The following sections describe how to configure a router ATM interface for point-to-point and point-to-multipoint connections. To configure the ATM interface, log in to the router, enter the privileged EXEC mode, and enter the commands in Example 5-14. Example 5-14 Base ATM Interface Configuration router(config-if) ip address 172.33.45.1 255.255.255.0 In some cases, the router interface identifier is in the form interface atm slot port-adapter 0 or interface atm number. To configure a new ATM...

Atm Lane

Cisco removed ATM LANE as a CCIE Routing and Switching lab exam topic but has retained it in the CCIE written blueprint, but with less emphasis. Know the LANE components and the SSRP that are used for redundancy. This section only covers LANE. Other ATM topics are covered in Chapter 5, Wide-Area Networks. LANE provides connectivity between Ethernet or Token Ring stations and ATM connected stations. LANE also provides connectivity for Ethernet or Token Ring stations across an ATM network. LANE...

Atm Lane Components

The components of ATM LANE are shown in Table 4-12. There is a LEC for each member of the ELAN. LECs implement LE-ARP address resolution and emulate a LAN for higher-level protocols. LEC builds a table to map MAC addresses to ATM addresses. Each LEC has an ATM address. LECs can be a computer station, switch, or router. The LES is the central resource for the ELAN. It provides management of all stations in the ELAN by providing address registration and resolution, and handling LE-ARP requests. A...

ATM Traffic Management

ATM connections support various service classes. The different service classes in turn support various network services. For example, video transmission uses a constant bit rate (CBR) class of service (CoS). Compressed voice service uses a real-time variable bit rate (RT-VBR). Data might use a non-real-time variable bit rate (NRT-VBR) type of traffic, or if the data device supports flow control, an available bit rate (ABR) traffic type. Low priority data might use an unspecified bit rate (UBR)...

Atomic Aggregate and Aggregator Attributes

The Atomic Aggregate attribute informs BGP peers that the local router is using a less specific (aggregated) route to a destination. If a BGP speaker selects a less specific route, when a more specific route is available, it must attach the Atomic Aggregate attribute when propagating the route. The Atomic Aggregate attribute lets the BGP peers know that the BGP speaker used an aggregated route. When you use the Atomic Aggregate attribute, the BGP speaker has the option to send the Aggregator...

B

B8ZS (Bipolar 8-zero substitution), 196 backbone routers, OSPF, 379 balanced signaling, 111 bandwidth, 42 Erlangs, 550 Frame Relay, CIR, 204 SRP, 198 VoIP networks, utilization tools, 556 beaconing, 124 Notification), 207 BGP (Border Gateway Protocol), 430 administrative distance, 437 attributes AS Path, 443 Atomic Aggregate, 446 local preference, 442 MED, 444-445 next-hop, 441-442 origin, 443 confederations, 453-456 filtering updates via AS path filters, 439-440 via communities, 437-438 via...

BGP Administrative Distance

The IOS assigns an administrative distance to eBGP and iBGP routes, as it does with other routing protocols. For the same prefix, the route with the lowest administrative distance is selected for inclusion in the IP forwarding table. Because iBGP learned routes do not have metrics associated with the route as IGPs (OSPF and EIGRP) do, iBGP learned routes are less trusted. The following are the administrative distances for BGP

BGP Communities

A group of policies can be applied to a community of networks or destinations with community filters. Each destination can belong to multiple communities. Communities provide a method to control distribution and filter routing information. The communities attribute is an optional, transitive, global attribute that is in the numerical range from 1 to 4,294,967,200. BGP communities are optional because BGP has the option to support the attribute. Transitive attributes are passed along to other...

BGP Decision Algorithm

The BGP decision algorithm can be summarized as follows 1 If no next hop, drop the path. 2 For internal path with synchronization, and the route is not in the IGP, drop the path. 7 Lowest origin type (IGP < EGP < Incomplete). 9 External path over Internal path. 10 Nearest eBGP neighbor (best IGP path to eBGP neighbor). IP address that reaches the destination Configured on the router to assign a preference of routes from different sources (not an RFC attribute) Number of autonomous systems...

BGP Decision Process

By default, BGP selects only a single path to reach a specific destination (unless you specify maximum paths). Cisco's implementation of BGP uses a simple decision process. When the path is selected, BGP puts the selected path in its routing table and propagates the path to its neighbors. To select the best path to a destination, Cisco routers running BGP use the following algorithm 1 If the specified next hop is inaccessible, drop the path. 2 If the path is internal, synchronization is...

BGP Neighbor Distribute Lists

Distribute lists also filter routes inbound or outbound to a neighbor. The list number is specified in the neighbor command, and access lists specify the networks to filter. Example 9-7 shows a distribute list that permits two networks from neighbor 1.1.1.1. Example 9-7 BGP Distribute List Configuration Example Example 9-7 BGP Distribute List Configuration Example access-list 99 permit 2.0.0.0 0.0.0.C access-list 99 permit 3.0.0.0 0.0.0.C

BGP Neighbors

BGP is usually configured between two directly connected routers that belong to different autonomous systems. Each AS is under different technical administration Usually, one is the enterprise company and the other is the service provider, or between different service providers, as shown in Figure 9-1. Before routing updates can be exchanged between two BGP routers, the routers must become established neighbors. After BGP routers establish a TCP connection, exchange information, and accept the...

BGP Path Attributes

BGP uses several attributes for the path selection process. BGP uses path attributes to communicate routing policies. BGP path attributes include the following next hop, local preference, number of AS path hops, origin, Multi-Exit Discriminator (MED), atomic aggregate, and aggregator. BGP attributes can be categorized as well-known or optional. Well-known attributes are recognized by all BGP implementations. Optional attributes do not need to be supported by the BGP process. Well-known...

BGP Peer Groups

Peer groups are a grouping of BGP neighbors that are applied to the same policies. The policies can be the following distribution list, route maps, next hop, update source, and so on. Peer groups can be assigned to iBGP peers or eBGP peers, but a peer group cannot contain both types of peers. The major benefit of a peer group is that it reduces the amount of CPU and memory resources on the router because it allows the routing table to be looked up once for update generation for all routers in...

BGP Redistribution

Another method to advertise BGP routes is to import them into the BGP routing table through redistribution of an IGP (such as OSPF and EIGRP). Both the network command and redistribution from an IGP add routes that are already in the IP table into the BGP table. You commonly use this method in large enterprise internetworks with iBGP cores. Filtering selects the redistributed prefixes and properly sets their attributes (especially origin). In Example 9-4, a route map specifies attributes to...

BGP Summary

The characteristics of BGP are summarized as follows Interdomain routing protocol. Uses TCP port 179 to establish connections with neighbors. eBGP for external neighbors. iBGP for internal neighbors. Uses several attributes for decision algorithm. Uses confederations and route reflectors to reduce BGP peering. Peer Groups apply policies to a group of routers Communities apply policies to a group of networks. MED (metric) attribute between autonomous systems to influence inbound traffic. Weight...

BGP Synchronization

By default, BGP synchronization is enabled on Cisco routers. If enabled, there must be a match for the network prefix in the routing table (from an IGP) for an iBGP path to be considered a valid path. If disabled, the router does not wait to check if the network prefix is in the routing table to advertise it to an external peer, or offer it to the IOS as a potential path. The purpose of synchronization is that if an AS provides transit service to another, BGP must not advertise a route for the...

Binary Numbers

The binary number system uses two digits 1 and 0. Binary numbers are primarily used by computer systems. IP addresses and MAC addresses are represented by binary numbers. The number of binary 1s or 0s is the number of bits. For example, 01101010 is a binary number with 8 bits. An IP address has 32 bits and a MAC address has 48 bits. Table 2-2 shows that IP addresses are usually represented in dotted decimal format therefore, it is helpful to know how to covert between binary and decimal...

Boot Flash

The Boot Flash, similar to boot ROM, stores the ROM monitor program and power-up diagnostics. Newer routers contain the boot program in Boot Flash rather than in a ROM chip. The ROM monitor performs important functions, such as system diagnostics, hardware initialization, and booting the operating system. The ROM monitor can also be used to recover passwords, change the configuration register, and download IOS images. The ROM monitor has a user interface that is recognized by the following ROM...

Bridges and Layer2 Switches

Bridges operate in the data-link layer of the OSI model. Bridges learn the MAC layer addresses of each node of the segments and remember off which port the MAC addresses are located. The bridge builds a table of MAC addresses and ports. If the destination MAC address of an incoming frame is not in the table, bridges forward the frame to all ports (minus the port from which the frame came). If the destination MAC address is in the table, bridges forward the frame only if the destination MAC...

Bridges and STP

Ethernet bridging occurs in the data-link layer of the OSI model. Switches perform the same function as bridges. For the rest of the chapter, the term switches refers to bridges. Bridges (and switches) forward frames from one interface to another based on the destination MAC address. For any incoming frame, bridges forward the frame out a specific port, if the destination MAC address is known, or it is flooded out all ports if the MAC address is unknown. If the destination MAC is unknown, the...

Car

CAR provides the means to limit the input or output transmission rate on an interface or subinterface based on traffic sources and destinations, while specifying policies for handling traffic that exceeds bandwidth allocations. Rate policies can be set based on IP access lists, IP Precedence, Media Access Control (MAC) addresses, or a QoS group. The difference between CAR and traffic shaping is that CAR is a policing scheme. CAR sets maximum limits on traffic but does not shape traffic to a...

CCIE Routing and Switching Exam Certification Guide

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 quotations in a review. Printed in the United States of America 1 2 3 4 5 6 7 8 9 0 First Printing July 2002 Library of Congress Cataloging-in-Publication Number...

Central Processing Unit CPU

Most Cisco routers have the Motorola 68000 series or Orion RISC (R4700) microprocessors. The CPU is the brain of the system. It runs route algorithms, exec processes, route filtering, network management, and so on. Some processes, such as Open Shortest Path First(OSPF), task the CPU with large computations. The CPU type can be checked with the show version command. Example 3-1 shows a Cisco MC3810 using the Motorola MPC860 processor. Example 3-1 show version Command Used to Check Processor Type...

Answers to Q A Section

1 What is the administrative distance of EIGRP external routes The administrative distance for internal EIGRP routes is 90. The administrative distance for external EIGRP routes is 170. 2 Which protocol do hosts use to join a multicast group Hosts use Internet Group Management Protocol (IGMP) to join a multicast group. IGMP operates between the host and the local router. 3 When redistributing EIGRP routes into RIP, how do the bandwidth and delay metrics get converted a. RIP assigns the...

Answers to Scenario Section

Use the following configuration to answer the scenario questions router bgp 200 redistribute ospf 100 route-map bgpospf route-map bgpospf permit 10 match tag 5 set metric 100 route-map bgpospf permit 15 match tag 6 set metric 200 1 How are the routes being manipulated a. OSPF 100 routes are redistributed into BGP 200 OSPF routes with a tag of 5 or 6 are set with a MED of 100 and 200, respectively. b. OSPF 100 routes are redistributed into BGP 200 a tag of 5 or 6 and metrics are set for the BGP...

Answers to Scenario Section Scenario

This scenario reviews your knowledge of RSRB. Knowledge of RSRB configurations and RIF constructs in RSRB environments is essential for the CCIE written test. Use Figure 4-34 to answer the following questions. 1 What is the RIF from Host A to Host C d. 0630.01b9.121d.0120 Answer b From Host A to Host C, a frame travels from Ring 0x01b, Bridge 0x9, Ring 21 (0x015), Bridge 13 (0xd), Ring 12 (0xc). 2 What is the RIF from Host A to Host B d. 0830.01b9.0155.00f0 Answer d From Host A to Host B, a...

Cisco Certification Areas

Cisco divides its certification program into three major areas and provides specialist certifications. Each area usually includes a certification at the associate, professional, and expert level the associate level certification is the lowest level and the expert level is the highest. The areas and certifications are as follows Network Installation and Support According to Cisco's web site, this path is for professionals who install and support Cisco technology-based networks in which LAN and...

Cisco OSPF Command and Configuration Handbook

Parkhurst, Ph.D., CCIE 2969 1-58705-071-4 Available Now Cisco OSPF Command and Configuration Handbook is the comprehensive OSPF protocol command and interior IP routing protocols command reference that is invaluable for network designers, engineers, and architects. This book contains numerous scenarios covering every possible command and presents clear and concise commentary on the purpose and context of each command.

Class A Addresses

Class A addresses range from 0 (00000000) to 127 (01111111) in the first octet. Network numbers assigned to companies range from 1.0.0.0 to 126.0.0.0, with networks 0 and 127 being reserved. For example, 127.0.0.1 is reserved for the local host. Also, network 10.0.0.0 is reserved for private addresses. By default, for Class A addresses, the first octet is the network number and the three remaining octets are the host number. In the format N.H.H.H, N is the network part and H the host part. With...

Class B Addresses

Class B addresses range from 128 (10000000) to 191 (10111111) in the first octet. Network numbers assigned to companies or other organizations range from 128.0.0.0 to 191.255.0.0. There are 16 networks reserved for private use these are shown later in this section. By default, for Class B addresses, the first two octets are the network number and the remaining two octets are for the host number. The format is N.N.H.H. With 16 bits available, there are 216 - 2 65534 IP addresses for host...

Class E Addresses

Class E addresses range from 240 (11110000) to 254 (11111110) in the first octet. These addresses are reserved for experimental networks. Network 255 is reserved for the broadcast address, such as 255.255.255.255. Table 6-3 summarizes the IP address classes. Table 6-3 summarizes the IP address classes.

Classless Versus Classful Routing Protocols

Routing protocols can be classified based on their support for classful or classless routing. Classful routing protocols do not advertise subnet masks in their routing updates therefore, the entire internetwork uses the configured subnet mask for the IP network. For example, if you use a classful routing protocol for network 130.170.0.0, the chosen mask (i.e., 255.255.255.0) has to be used on all router interfaces using the 130.170.0.0 network. Serial links and local-area networks are...

Codecs

Codecs transform analog signals into a digital bit stream and digital signals back into analog signals. In this case, it specifies the voice coder rate of speech for a dial peer. Figure 12-3 shows an analog signal that is digitized with a coder for digital transport. The decoder converts the digital signal into analog form. Codecs are presentation layer protocols. The default codec setting for VoIP is G.729 (g729r8). Some other codec standards are listed in Table 12-2. The default codec setting...

Committed Information Rate CIR

Frame Relay is usually leased by carriers with a contract that bandwidth is guaranteed up to a maximum limit. Although the CIR guarantees the rate, the user traffic can burst to higher rates, if the provider's frame relay network is underutilized. The CIR is defined in two ways, and its use depends on the Frame Relay provider's implementation. The CIR is either the maximum speed that the Frame Relay provider transfers information for each PVC, or it is the average rate (in bps) at which the...

Confederations

Another method to reduce the iBGP mesh within an AS is to use BGP confederations. With confederations, the AS is divided into smaller, private autonomous systems, and the entire group is assigned a confederation ID. The routers within each private AS are configured with the full iBGP mesh. Each private AS is configured with eBGP to communicate with other semi-autonomous systems in the confederation. Only the AS number of the confederation is seen by external autonomous systems, and this number...

Configuration File Manipulation

The router configuration can reside in several locations NVRAM, DRAM, terminal, or on a TFTP server. When the router is booted, the configuration stored in NVRAM is the startup configuration. After the router is booted, the configuration is placed in DRAM. When users attaches to the console or telnets to the router, they view the active configuration on the terminal. The configuration file can also be transferred to or from a TFTP server. Figure 3-2 shows the commands that manipulate the...

Configuration Mode

In enable mode, you can enter configuration mode with the configure terminal command. You use configuration mode for interface, router, and line configuration Enter configuration commands, one per line. End with CNTL Z. routerlab(config) If an interface is configured, the prompt changes as follows router1(config) interface ethernet 0 If a routing protocol is configured, the prompt changes as follows router1(config) router rip router1(config-router) exit router1(config) router eigrp 100...

Congestion Control

Frame Relay has few control and error mechanisms as compared with X.25, but these have been sufficient, and in fact, contribute to the popularity of the protocol. The following are methods that determine or reduce congestion and errors in the network Forward explicit congestion notification (FECN) Backward explicit congestion notification (BECN) When a router sends a frame into the Frame Relay network, it can traverse many switches. If the frame reaches a switch that is experiencing congestion,...

Connection Establishment

TCP connections are established between two systems by synchronizing with each other's initial sequence numbers. This is accomplished by an exchange of connection-establishing segments with the SYN bit set and initial sequence numbers. The TCP connection is full-duplex each side sends its own initial sequence number and must receive an acknowledgment from the other side. Figure 6-6 shows the three-way handshake for connection establishment. Figure 6-6 Three-Way Handshake for Connection...

Connection Flow Control

After a connection is established, the sending TCP sends segments no larger than the received window size. The sender waits for the acknowledgment of sent segments before sending additional data. Each acknowledgment also has the window size, which indicates the amount of data that the receiver is willing to accept. The window can change in size, therefore, the name sliding window. Remember, the window size is represented in bytes. A TCP sender, for example, might have 200 bytes to send to a...

Connection Termination

A connection can terminate in two ways. The first is graceful termination, and the second is an For graceful connection termination, both sides must send a finish (FIN) signal and expect an acknowledgment from the other side. It is similar to connection establishment, but in this case, it is a connection termination. It takes four, not three, segments to terminate a connection. Because the connection is full-duplex, each side must shut down independently. Either side can send a FIN to terminate...

Contents at a Glance

Chapter 1 CCIE Certification, Test Preparation, and Using This Book 3 Chapter 2 Networking Concepts Review 15 Chapter 3 Cisco Equipment Operations 61 Chapter 4 Local-Area Networks and LAN Switching 105 Chapter 7 Static Routing and Distance Vector Routing Protocols 319 Chapter 8 IP Link-State Routing Protocols 371 Chapter 9 Border Gateway Protocol 427 Chapter 10 Administrative Distance, Access Lists, Route Manipulation, and IP Multicast 473 Chapter 11 Traffic Management 513 Chapter 12...

Converting Binary to Decimal

To convert a binary number to decimal, multiply each instance of 1 by the power of 2. Table 2-4 shows that each bit in the binary number 11111111 has a decimal equivalent from 1 to 128, which is based on the location of the bit in the binary. This is similar to decimal numbers where the numbers are based on 1s, 10s, 100s, and so on. In decimal format, the number 111 is 100+10+1. In binary format, the number 11111111 is the sum of 128+64+32+16+8+4+2+1 255. For 10101010, this results in...

Converting Binary to Hexadecimal

To convert binary numbers to hex, group the bits into groups of four, starting with the right-justified bits. Groups of four bits are usually called nibbles. Each nibble has a hex equivalent. The following are some examples. Conversion Example 9 Convert 0010011101 to Hex Conversion Example 10 Convert 0010101001011001000010110001 to Hex 0010 1010 0101 1001 0000 1011 0001 Answer 2A590B1h

Converting Decimal to Binary Numbers

This procedure is similar to converting from hex to decimal (by dividing), but now you divide the decimal number by 2. You use each residual to build the binary number. Each residual bit is prepended to the previous bit starting with the right. Repeat the procedure until you cannot divide anymore. The only problem is that for large numbers you might have to divide many times. An alternate method follows the next example. Conversion Example 16 Convert 26 to Binary The first bit is 0 now divide...

Converting Decimal to Hexadecimal

First things first, memorize Table 2-1. For larger numbers, there are two methods. The first method is to convert decimal to binary and then from binary to hex. The second method is to divide the decimal number by 16 the residual is the right-most bit. Then keep dividing until the number is not divisible. For the first method, use the schemes described in later sections. For the second method, follow the examples described here. First, divide the decimal number by 16. The residual is the first...

Converting Hexadecimal to Decimal

To convert a hex number to decimal, take the right-most digit and convert it to decimal (i.e., 0xC 12). Then add this number to the second right-most digit x 16 and the third rightmost digit x 256. Don't expect to convert numbers larger than 255 on the CCIE written exam because the upper limit of IP addresses in dotted decimal format is 255, although Token Ring numbers do reach 4096. Some examples follow. Conversion Example 5 Convert 177h to Decimal 1 x 256 256 7 x 16 112 7 x 1 _7_ 375d...

Crb

CRB enables the router to both route and bridge the same protocol on separate interfaces. With IRB, a protocol can be routed between routed interfaces, bridged interfaces, or different bridge groups. The access list numbers for MAC address filters are from 700 to 799. The access list for EtherType filters are from 200 to 299. The source determines the route to use to reach the destination node before sending an information frame to it. The bridge does not store MAC addresses. Limited to 7...

Data Link Connection Identifier DLCI

Frame Relay uses the DLCI to identify VCs. Each DLCI has local significance. The DLCI number at Router A can be different than the DLCI number at Router B for the same PVC. As shown in Figure 5-6, each router uses the local DLCI number to reach another through the Frame Relay network. Router A uses DLCI 200 to reach Router B, DLCI 300 to reach Router C, and DLCI 400 to reach Router D. The DLCI is configured for each interface or subinterface to mark the appropriate PVC. For example, the...

Data Link Layer OSI Layer

This layer is concerned with the reliable transport of data across a physical link. Data at this layer is formatted into frames. Data-link specifications include the following sequencing of frames, flow control, synchronization, error notification, physical network topology, and physical addressing. This layer converts frames into bits when sending information and converts bits into frames when receiving information from the physical media. Bridges and switches operate in the data-link layer....

Ddistance ospfexternal 120

The distance external command can assign an administrative distance, which is different than the default (110), to OSPF external routes. 13 When redistributing between EIGRP and IGRP on the same router, which statement is correct a. If the AS numbers are the same, you use the redistribute command. b. If the AS numbers are the same, you do not use the redistribute command. c. If the AS numbers are different, you use the redistribute command. If EIGRP and IGRP are configured with the same AS...

Debug

The debug commands are available only in privileged exec (enable) mode. If you attempt to use debug in user exec mode, the command is not recognized. You must use debug commands with caution because the router's CPU use significantly increases when debugging is enabled. NOTE If you access the router through a virtual terminal, such as Telnet, you need to enter the terminal monitor command to have debug output show on your screen. This command is not necessary if you access the router from the...

Designated IS DIS

As with OSPF, IS-IS selects DISs on multiaccess networks. There is no backup DIS as in OSPF. If the DIS fails, a new DIS is elected. L1 and L2 DISs are selected separately and might or might not be the same IS. One difference between OSPF and IS-IS in multiaccess subnetworks is that all IS-IS ISs establish adjacencies with all others in the subnetwork, not just with the DIS. The IS with the highest priority becomes the DIS. By default, the priority value is 64. The priority value can be changed...

Designated Routers

Although not an OSPF router type, some routers on multiaccess networks (such as Ethernet or multipoint Frame Relay) are selected as DRs. The purpose of the DR is to collect all LSAs for the multiaccess network and to forward the LSA to all non-DR routers. This reduces the amount of LSA traffic generated on an Ethernet network. A router can be the DR for one multiaccess network and not the DR in another attached multiaccess network. The DR also floods the Network LSA (Type 2) to the rest of the...

Determining the Network Portion of an IP Address

If you have an IP address and subnet mask, you can determine the full classful network, subnetwork, and broadcast number of the subnetwork. This is accomplished by a logical AND operation between the IP address and subnet mask. Table 6-8 shows the AND operation. The AND operation is similar to the multiplication of Bit 1 and Bit 2 if any 0 is present, the result is 0. As an example, take the IP address 200.1.1.70 with a subnet mask of 255.255.255.224. The three bolded bits in the subnet mask...

Dial Backup Configuration

ISDN can back up a primary circuit if it fails or has exceeded a use threshold. If the primary fails, the ISDN circuit is enabled. While the connection is up, IP traffic is passed through the backup interface. Also, the backup BRI can be enabled if the primary circuit reaches a certain load. In Example 5-11, the BRI is enabled if serial 0 reaches 60 percent load or if serial 0 is down for 25 seconds. The BRI is disabled if serial 0 is back up for 60 seconds or if the bandwidth in the primary is...

Distribute lists filter the contents inbound or outbound of routing updates

9 Which access list permits all hosts in network 192.172.100.0 28 a. access-list 100 permit 192.172.100.0 0.0.0.31. b. access-list 10 permit 192.172.100.0 255.255.255.240. c. access-list 10 permit 192.172.100.0 0.0.0.31. d. access-list 10 permit ip 192.172.100.0 0.0.0.31. Answer c b. Protocol Independent Multicast c. Protocol Independent Management d. Password Independent Multicast Answer b

Dns

NetBIOS Name Server (UDP 137) NetBIOS Datagram server (UDP 138) BOOTP Server and Client (UDP 67 and 68) IEN-116 Name Service (UDP 42) To prevent and control the forwarding of other protocols, you use the no ip forward-protocol udp port command. This is a global command and is not configured on an interface. For example, to forward TFTP, BOOTP, Terminal Access Controller Access Control System (TACACS), and a DNS broadcast, and prevent the other default protocols, you configure the router as...

Do I Know This Already Quiz

The purpose of this assessment quiz is to help you determine how to spend your limited study time. If you can answer most or all of these questions, you might want to skim the Foundation Topics section and return to it later as necessary. Review the Foundation Summary section and answer the questions at the end of the chapter to ensure that you have a strong grasp of the material covered. If you intend to read the entire chapter, you do not necessarily need to answer these questions now. If you...

Dscp

DSCP, which is defined in RFC 2474, provides for 64 values (26) for prioritization by using the six most-significant bits of the IP ToS field. DSCP replaces the ToS field with the DSCP field, as shown in Figure 11-5. You can use DSCP for packet classification for later policing. With DSCP, service providers can classify packets into more service levels (CoS) than the eight levels possible with the IP Precedence bits. Figure 11-5 DSCP Field Replaces the ToS Field Consult RFC 2474, Definition of...

Dynamic Packet Transport DPTSpatial Reuse Protocol SRP

DPT is a Cisco developed, resilient optical packet ring technology that is optimized for data transmission. DPT uses dual, counter-rotating rings that are referred to as inner and outer, which can be used for data and control packet transmission concurrently. DPT operates by sending the data packets in one direction on one fiber ring and the corresponding control packets in the opposite direction on the other fiber ring. The full capacity of the fiber rings can be utilized for data and control...

Eigrp

EIGRP was released in the early 1990s by Cisco Systems as a evolution of IGRP toward a scalable routing protocol. EIGRP is a classless protocol that permits the use of VLSMs and support for CIDR for scalable allocation of IP addresses. Routing updates are not sent periodically, as in IGRP. EIGRP allows for authentication, with simple passwords or with MD5. EIGRP autosummarizes networks at network borders and can load balance over unequal-cost paths. Packets use IP protocol 88. You can use only...

EIGRP can be configured to use up to six equalcost paths

15 Which command configures custom queuing on an interface Custom queuing is configured by creating queues with the queue-list protocol command, assigning byte counts to the queues with the queue-list queue byte-count command, and then configuring the interface with the custom-queue-list command. 16 Priority queuing uses how many queues Priority queuing uses four queues high, medium, normal, and low. 17 Which queuing strategy forwards frames based on the order that they are received First-in,...

EIGRP Configuration

The configuration commands for EIGRP are similar to IGRP. After configuring the interfaces, the router eigrp command enables the routing protocol. The networks are defined with the network command. Using the physical network described in Figure 7-6, the configurations for Router8, Router9, and RouterlO are presented in this section. Figure 7-6 EIGRP Configuration Example Example 7-26 shows the configuration of Router8. EIGRP is configured with the autonomous system number 100. EIGRP hellos are...

EIGRP Packet Types

EIGRP uses the following packet types Hello packets assist in the discovery of EIGRP neighbors. The packets are multicast to 224.0.0.10. By default, hello packets are sent every 5 seconds (60 seconds on WAN links with 1544 Mbps speeds or less). An acknowledgment packet acknowledges the reception of an update packet. An acknowledgment packet is a hello packet with no data. Acknowledgment packets are sent to the unicast address of the sender of the update packet. Update packets contain the...

EIGRP Summary

The characteristics of EIGRP are summarized as follows Hybrid routing protocol (distance vector that has link-state protocol characteristics). Classless protocol (supports VLSMs). Default composite metric of bandwidth and delay. Load and reliability can be factored into the metric. Sends partial route updates only when changes occur. Support for authentication. Uses DUAL for loop prevention. By default, equal-cost load balancing unequal-cost load balancing with the variance command....

Encoding Schemes of T1s and E1s

Bipolar 8-zero substitution (B8ZS) is a T1 carrier line code in which bipolar violations are deliberately inserted if the data contains a string of 8 or more consecutive 0s. B8ZS ensures a sufficient number of transitions to maintain system synchronization when the user data stream contains an insufficient number of 1s. The European hierarchy uses B8ZS at the T1 rate. Alternate mark inversion (AMI) is a T1 carrier line code in which 1s are represented by positive or negative voltage,...

Encryption

Encryption is the process of taking cleartext data and encoding it in such a way that only the system with a certain key can decode it. The data is encoded by the sender, transmitted over unsecured lines, and decoded by the receiver. Data is encrypted for various reasons, such as to protect data privacy and provide data integrity. Keys are a sequence of digits that encrypt and decrypt data. The longer the key length, the less likely an unauthorized person or system can decrypt the data....

Example of Layered Communication

If you use a Telnet application, Telnet maps into the top three layers of the OSI model. Figure 2-3 shows that a user on Host 1 enables the Telnet application to access a remote host (Host 2). The Telnet application provides a user interface (application layer) to network services. As defined in Request For Comments (RFC) 854, ASCII is the default code format used (presentation layer). There is no session layer defined for Telnet it is not an OSI protocol. Per the RFC, Telnet uses TCP for...

Extended access lists range from 100 to 199 Answer c uses the correct format

8 In an internetwork of 50 routers running EIGRP, you need to filter the networks received by one spoke router. What can you use a. Use an access list and apply it to the inbound interface with the ip access-group command. b. Redistribute the routes into OSPF with a route map. c. Use a distribute list under the EIGRP process with an access list to filter the networks. d. Change the administrative distance of the router. 99 deny tcp any any eq echo log 99 deny tcp any any telnet eq telnet 99...

External Path Types

External paths can be Type 1 or Type 2. Do not confuse these with the router and network LSAs. By default, external routes Type 2. The metric of Type 2 external routes is the metric of the route at the point of redistribution into the OSPF network. Type 1 external routes have a metric that is the sum of the redistribution cost plus the cost of the path to reach the ASBR. To set the external metric type for external routes, use the metric-type keyword in the...

Fast Ether Channel FEC

Cisco's FEC provides a method to increase the bandwidth between two systems by bundling FE links. FEC also provides load sharing and redundancy capabilities. If a link fails in the FEC bundle, the other links take on the rest of the traffic load. Although this discussion focuses on FE, EtherChannel works for 10 Mbps Ethernet links and for GE links. The requirements for EtherChannel are that all ports must be of the same speed, be in duplex mode, and belong to the same VLAN. Up to four ports are...

Feedback Information

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Fifo

This queuing method does not implement any sophisticated schemes. With FIFO, packets are sent out in the order that they are received. No prioritization occurs for any traffic. To check an interface's queuing method, use the show interface command. Next, check the queuing strategy output. The router output in Example 11-1 shows an Ethernet interface using FIFO. Example 11-1 Interface Using FIFO Queuing R4 show interface Ethernet0 is up, line protocol is up Hardware is PQUICC Ethernet, address...

Figure 614 DNS Tree

UDP is the recommended transport protocol for DNS queries. TCP is the recommended protocol for zone transfers between DNS servers. A DNS query searches for the IP address of a Fully Qualified Domain Name (FQDN), such as www.cisco.com. SNMP is a network protocol for the management of network devices. SNMP allows network managers to inspect or change parameters on a device remotely. SNMP was first defined by RFC 1067 (SNMPvl), which was succeeded by RFCs 1155, 1157,...

Figure 619 IP Header

E Experimental reserved 1111xxxx 240.0.0.0 to 254.255.255.255 E Experimental reserved 1111xxxx 240.0.0.0 to 254.255.255.255 Class Class C 11111111 11111111 11111111 00000000 255.255.255.0 C 11111111 11111111 11111111 00000000 255.255.255.0 Table 6-24 Address Assignment and Summarization Table 6-24 Address Assignment and Summarization A single subnet mask for the entire IP network number. Permits the use of different subnet masks for a network number. Routing protocols can aggregate subnet...

Flash Memory

Flash memory allows you to store and delete IOS images without having to change a ROM chip. The file is stored even if the router is turned off. If capacity allows, multiple images can be stored in flash. The image that gets loaded during the boot process is the one identified in the boot system configuration commands. Flash memory can be internal or external. The external flash system uses Personal Computer Memory Card International Association (PCMCIA) cards inserted into slots on the router....

Foundation Summary

The Foundation Summary is a condensed collection of material that provides a convenient review of key concepts in this chapter. If you are already comfortable with the topics in this chapter, this summary will help you recall a few details. If you just read the Foundation Topics section, this review should help solidify some key facts. If you are doing your final preparation before the exam, these materials are a convenient way to review the day before the exam. Provides the user or operating...

Foundation Topics Administrative Distance

On routers running several IP routing protocols, two different routing protocols might have a route to the same destination. Cisco routers assign each routing protocol an administrative distance. The default values are shown in Table 10-1. In the event that two or more routing protocols offer the same route for inclusion in the routing table, the Cisco IOS selects the route from the routing protocol with the lowest administrative distance. Table 10-1 Default Administrative Distances for IP...

Foundation Topics BGP Review

This section covers BGP theory and design concepts. The current version of BGP, version 4 (BGP4), is defined in RFC 1771 (March 1995). BGP is an interdomain routing protocol. The primary function of BGP is to provide and exchange network reachability information between domains or autonomous systems. BGP uses TCP port 179 as its transport protocol between BGP peers or neighbors. BGP4 was created to provide classless interdomain routing (CIDR), a feature that was not present in the earlier...

Foundation Topics OSPF

It is a link-state routing protocol that uses Dijkstra's shortest path first (SPF) algorithm to calculate paths to destinations. In OSPF, each router sends link-state advertisements about itself and its links to all its adjacent routers. Each router that receives a link-state advertisement records the information in its topology database and sends a copy of the link-state advertisement to each of its adjacencies (other than the one that originally sent the...

Foundation Topics Static Routes

Before discussing dynamic routing protocols, this section reviews the configuration of static routing protocols. Static routes are manually configured. For each change in the network topology, an administrator must manually change the static routes as necessary. You can use static routes in hub-and-spoke networks with low bandwidth links so that bandwidth is not used by routing protocols. You can also use static routes in network firewall architectures and at connections with external partners.

Frame Relay

This section covers the Frame Relay topics that are listed in the blueprint of the CCIE written test. Frame Relay is a Layer-2 WAN service that sends information in frames. Each frame has an address that the network uses to determine the destination of the frame. Frame Relay was developed when lines became more reliable and the high-overhead link error checking that is found in X.25 was no longer required. This provided more available bandwidth for WAN connectivity. Similar to X.25, Frame Relay...