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...

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...

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...

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 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 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 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)...

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 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 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...

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...

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...

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 Which queuing scheme can be used to SNA traffic before servicing other traffic types Priority queuing (PQ) always empties the high queue before servicing the lower priority queues. 2 Which protocol permits hosts to request quality of service parameters from network resources The Resource Reservation Protocol (RSVP) is a signaling protocol that enables hosts to obtain special qualities of service for data traffic. 3 Which mechanism drops packets to prevent congestion Weighted random early...

Answers to Scenario Section

Answer the following questions based on Figure 2-11. Each question tests your knowledge of how different metrics affect the chosen route to a destination. 1 A user performs a Telnet from PC 1 to PC 2. If the metric that the configured routing protocol uses is bandwidth, which route will the packets take 1 A user performs a Telnet from PC 1 to PC 2. If the metric that the configured routing protocol uses is bandwidth, which route will the packets take c. Neither, there is not sufficient...

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 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.

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...

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...

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 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...

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...

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...

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...

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...

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....

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...

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...

F

Fairness algorithm, SRP, 198-199 Fast Ethernet, 118-119 100Base T4, 119-120 100Base TX, 119 100BaseFX, 120 Fast-Leave Processing (CGMP), 494 FD (feasible distance), 353 FEC (Fast EtherChannel), 158 configuring, 159 FECN (Forward Explicit Congestion Notification), 207 FGCRA (Frame Based Generic Cell Rate Algorithm), 234 FHSS (Frequency Hopping Spread Spectrum), 128 field definitions IP header, 269-271 RIPv1 messages, 325 RIPv2 messages, 332 TCP header, 282-283 Token Ring frames, 126-127 UDP...

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...

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...

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...

Frame Relay Frame Format

Frame Relay uses Link Access Procedure for Frame Relay (LAPF) for frame format. LAPF is yet another variation of the HDLC frame format it supports Frame Relay. There is no control frame, flow control, and error control, and no sequence numbers. Figure 5-7 shows the LAPF frame format. Figure 5-7 Frame Relay LAPF Frame Format Figure 5-7 Frame Relay LAPF Frame Format Address sub-fields Bits 8 7 6 5 4 3 2 The 10-bit DLCI provides the PVC identifier, which has local significance between the router...

Frame Relay LMI Frame Relay Format

The LMI frame format is shown in Figure 5-8. Table 5-2 describes the fields of the LMI frame. Table 5-2 LMI Fields Table 5-2 describes the fields of the LMI frame. Table 5-2 LMI Fields The LMI DLCI is 1023 if you use a cisco-type LMI. It is 0 if you use either Unnumbered Information Indicator sets the poll final bit to 0. Protocol Discriminator contains a value indicating that the frame is an LMI Call Reference. This field always contains 0s and is not currently used. Status-inquiry message...

Frame Relay map Command

Before Inverse ARP was available (prior to 11.2), the most common method to configure Frame Relay was by using map statements. Looking at Figure 5-9, the serial interface configuration for Router A is displayed in Example 5-3, and the configuration for Router B is displayed in Example 5-4. Example 5-3 Router A Frame Relay Map Configuration Example Figure 5-9 Frame Relay Map Configuration Figure 5-9 Frame Relay Map Configuration Example 5-4 Router B Frame Relay Map Configuration Example...

Frame Relay show Commands

The most common commands that observe Frame Relay status and configuration are the following This section shows and explains sample outputs from each of these commands. Example 5-5 shows output from the show frame-relay map command. Example 5-5 show frame-relay map Command The output from the show frame-relay map command shows the current status and relevant information about the mappings. Example 5-5 shows two VCs mapped on serial 0. One has local DLCI 103, IP is the network protocol in use,...

Frame Relay Traffic Shaping FRTS

FRTS allows for the management of traffic congestion in Frame Relay networks. FRTS-enabled routers use received BECN information as input to manage the outbound traffic. FRTS is enabled on the major interface, and traffic classes are defined in global configuration. A traffic class is applied to each subinterface as it applies. You can use FRTS in several ways for rate enforcement on an individual VC by configuring the peak transmission rate, to dynamically throttle traffic on a VC when BECNs...

Hierarchical Model for Networks

The use of a hierarchical design for networks facilitates the operation and management of the internetwork. With a hierarchical design, the network is easier to understand, the network can scale up as size requirements grow, it is easier to implement service policies, and troubleshooting network problems are simplified. The IP addressing assignment is accomplished by following a hierarchy that maximizes route summarization. Routing protocols can aggregate addresses into summary routes, which...

Hot Standby Routing Protocol HSRP

HSRP is not a TCP IP standard defined by an RFC instead, it is a Cisco protocol that provides automatic router backup. HSRP allows one router to assume the function of a second router if the second router fails. HSRP is useful for critical networks that need a failover router for network reachability. HSRP uses a priority scheme to determine the default active router. The default priority is 100. If you configure a router with a higher priority, it becomes the active router if both routers are...

Hubs and Repeaters

Repeaters operate in the physical layer of the OSI model. They basically repeat the data (bits) from one port to all other ports. Hubs are repeaters with many ports that were created to concentrate the wiring into a communication closet. These devices are not aware of frames or packets they amplify the signal and send out all ports. Repeaters do not delineate broadcast or collision domains. Figure 2-5 shows that all devices connected to a repeater are in the same collision domain they all...

IBGP

IBGP describes the peering between BGP neighbors in the same autonomous system(AS). You use iBGP in transit autonomous systems. Transit autonomous systems forward traffic from one AS to another AS. If you do not use iBGP in transit autonomous systems, the eBGP learned routes are redistributed into an IGP and then redistributed into the BGP process in another eBGP router. iBGP provides a better way to control the routes for the transit AS. With iBGP, the external route information (attributes)...

IGRP Configuration

The configuration commands for IGRP are as simple as for RIPvl. After configuring interfaces, use the router igrp command. You use an autonomous system number with the command because multiple instances of IGRP can be configured in a Cisco router. The configuration for the routers in this section is shown in Figure 7-5. Example 7-18 shows the configuration for Router8. IGRP 100 is enabled with the router igrp 100 command. The network 172.16.0.0 specifies that all interfaces on this router with...

Initial Configuration Dialog

At bootup, the router prompts the user to enter into the system configuration dialog if the router has no configuration (because it is new or because the configuration file was erased by the write erase command ). In Example 3-8, the router output shows a sample of the configuration dialog. If you enter the dialog, a series of questions walk you through the configuration of the router. In Example 3-8, you enter the basic network management configuration. The first level of configuration is...

IP Access Lists

Many uses exist for IP access lists on Cisco routers and switches. You use access lists to control access to networks and virtual local-area networks (VLANS), to redistribute or filter routes in route maps, and so on. An access list defines a set of criteria that can be applied to every packet processed by the router or switch. When applied to an interface, an access list can block or permit traffic forwarding. The access list can be applied at the ingress (inbound) or at the egress (outbound)...

IP Address Subnets

Subnetting plays an important part in IP addressing. The subnet mask helps determine the network, subnetwork, and host part of an IP address. The network architect uses subnetting to manipulate the default mask to create subnetworks for LAN and WAN segments. As mentioned earlier, one router interface with 16 million hosts off that interface is not a good thing. Subnet masks are for Class A, B, and C addresses only. Multicast addresses do not use subnet masks. Subnet masks are a 32-bit number...

IP Addressing

This section covers the IP address classes, network subnets, and address assignments. The CCIE candidate must be an expert in handling IP addresses. IP addresses assign a unique logical number to a network device. The number is 32-bits long. To make the number easier to read, you use the dotted decimal format. The bits are combined into four 8-bit groups, each converted into decimal numbers that are separated with dots. The following example shows an IP address in binary and decimal formats...

IP Header

The best way to understand IP is to know the IP header. Segments from TCP are passed on to IP, and an IP header is added to the data. Figure 6-2 shows the IP header format. The following is a description of each field in the IP header Version This field is 4 bits long and indicates the format, based on the version number, of the IP header. Version 4 is the current version, so this field is set to 0100. IHL This field is 4 bits long and indicates the length of the header in 32-bit words (4...

Pv6

Cisco added IPv6 to the CCIE written exam blueprint. You need to become extremely familiar with its specifications. The driving motivation for the adoption of a new version of IP is the limitation imposed by the 32-bit address field in IPv4. In the 1990s, there was concern that the IP address space would be depleted soon. Although CIDR and NAT slowed down the deployment of IPv6, its standards and potential deployments are maturing. The IPv6 specification provides 128-bits for addressing a...

ISDN Layer2 Protocols

At Layer 2 the ISDN B channels can be encapsulated with X.25, Frame The D channel is encapsulated with LAPD or X.25. These protocols are ISDN uses LAPD as the signaling protocol at Layer 2. LAPD is specified in the ITU-T Q.921 standard. You use LAPD on the D channel to ensure proper flow and transmission of the signaling and control information. The LAPD frame format is shown in Figure 5-12. The address field is similar to the address field in HDLC. The Service Access Point Identifier (SAPI)...

ISIS Areas

IS-IS uses a two-level hierarchy that is similar to the OSPF areas. ISs are configured to route L1, L2, or both L1 and L2 routes (L1 L2). L1 ISs are similar to OSPF internal routers. An L2 IS is similar to an OSPF backbone router. An IS that has both L1 and L2 routes is similar to an OSPF ABR. Each L1 IS in an area has an identical link-state database. The L1 L2 ISs maintain a separate link-state database for the L1 routes and L2 routes. The L1 L2 ISs do not advertise L2 routes to the L1 area....

ISIS Configuration

Configuration for IS-IS is relatively simple. An IS-IS process is created by using the router isis tag command. Only one IS-IS process performing L2 routing is allowed per IS, and that process can also perform L1 routing. However, multiple L1-only IS-IS routing processes can be configured (up to 29 additional L1-only processes). If the tag value is not specified, a null tag is assumed. If multiple L1 routing processes are configured, each is labeled with a tag to facilitate area identification....

Load Balancing

The Cisco blueprint lists load balancing as a performance management topic. Load balancing support for each routing protocol is covered in Chapter 7, Static Routing and Distance Vector Routing Protocols, Chapter 8, IP Link-State Routing Protocols, and Chapter 9, Border Gateway Protocol. For easy reference, Table 11-2 lists the load balancing capabilities covered on each routing protocol. Enhanced Interior Gateway Protocol (EIGRP) Unequal-cost load balancing up to six paths Equal-cost load...

Local Management Interface LMI

LMI is a set of enhancements to the original Frame Relay specification. The LMI extensions include global addressing, virtual-circuit status messages, and multicasting. With LMI, control messages are sent between the DTE and DCE proving status information about the switch and PVCs. NOTE The LMI type is significant between the local router and connecting Frame Relay switch. The remote router-switch pair can implement a different LMI format. There are three types of LMI implementations. The LMI...

Local Preference Attribute

The local preference attribute indicates which path to use to exit the AS. It is a well-known discretionary attribute used between iBGP peers and not passed on to external BGP peers. In the IOS, the default local preference is 100 the higher local preference is preferred. The default local preference is configured on the BGP router with an external path. It then advertises its local preference to iBGP peers. An example of the local preference attribute where Routers B and C are configured with...

Local Area Networks and LAN Switching

This chapter covers the CCIE Written blueprint objectives related to bridging, local-area networks, and LAN switching. Other blueprint topics covered in this chapter include ATM LANE and LAN security. 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...

Multiprotocol Label Switching MPLS

MPLS provides ways to perform traffic engineering, to guarantee bandwidth or set paths, and to enable Virtual Private Networks (VPNs). It specifies ways that Layer-3 traffic can be mapped to connection-oriented Layer-2 transport protocols, such as ATM. It adds a label containing specific routing information to each IP packet that directs traffic through explicitly defined paths, and it allows managers to implement policies that assign labels to various CoS. This enables the managers to offer...

N

NAT (Network Address Translation), 299-300 NBAR (Network-Based Application Recognition), 531 NCP (Network Control Protocol), 220, 568 NDS (Netware Directory Services), 569 neighbors AS number filtering, 439-440 eBGP peer relationship, 433-434 iBGP peer relationship, 432-433 peer groups, 449 route filtering, 438 verifying established connections, 431 verifying neighbor establishment, 431 EIGRP, discovery process, 346 NetBIOS, 569 Windows NT implementation, 575-576 NETs (network entity titles),...

Network Layer OSI Layer

The network layer is concerned with the routing of information and methods to determine paths to a destination. Information at this layer is called packets. Specifications include routing protocols, logical network addressing, and packet fragmentation. Routers operate in this layer. The CCIE lives and dies in this layer. Examples of network layer specifications are the following Routing Information Protocol (RIP) Open Shortest Path First (OSPF) Enhanced Interior Gateway Routing Protocol (EIGRP)...

Numeric Conversion

This section focuses on the techniques used to convert between decimal, binary, and hexadecimal numbers. Although there might not be a specific question on the exam that asks you to convert a binary number to decimal, you need to know how to convert these numbers to complete problems on the test. A diagram might show a Token Ring with a decimal number but the RIF might be shown as hexadecimal. An IP address might be shown as binary or in dotted decimal format. Some show commands have output...

OSPF Configuration

This section covers the configuration of OSPF routers and the commands that you use to verify OSPF routes. Use Figure 8-6 as a reference, where four routers are configured to run OSPF using area 0 and three other areas. Area 10 is configured to do authentication and has a Frame Relay link. Area 30 is connected to area 0 through a virtual link. Area 20 is a transit area with a p2p link. Router 3 is configured with a higher priority so that it is elected as the DR for the Ethernet segment. The...

OSPF Router Types

OSPF defines several router types that are related to their place and function in the area architecture. Figure 8-2 shows a diagram of OSPF router types. The following is a list of explanations for each router type in Figure 8-2 Internal router Interface belongs to the same OSPF area and keeps only one link-state database. Area border router (ABR) Connects to more than one area maintains a link-state database for each area that it belongs to and generates summary LSAs. Autonomous system...

Password Recovery

Router password recovery is accomplished by rebooting the router and breaking into ROM monitor mode, setting the device to ignore the configuration file, rebooting, canceling the Initial Configuration Dialog, configuring memory, and then reading or resetting the password. You must be familiar with the password recovery steps for the test. The following procedure is from Cisco's web site. This is the procedure for routers using Reduced Instruction Set Computer (RISC)-based processors Step 1 Turn...

Pim

PIM comes in sparse mode (PIM-SM) and dense mode (PIM-DM). As the names imply, the first operates in sparse mode and the second in dense mode. PIM-DM uses a technique known as reverse path forwarding (RPF). When the router receives a packet, it forwards it out all other interfaces, which allows the data stream to reach all segments. If no hosts are members of a multicast group on any of the router's attached or downstream subnets, the router sends a prune message up the distribution tree to...

PPP Authentication

The two types of authentication that you can use are the Password Authentication Protocol (PAP) and the Challenge Authentication Protocol (CHAP). PAP was developed earlier and uses cleartext passwords, thus leaving password open to be seen in protocol analyzers. CHAP, described in RFC 1994, uses encrypted passwords. CHAP uses a three-way challenge-response handshake to authenticate between the ESs. This is done upon initial link establishment and can be...

Q A

The Q & A questions are more difficult than what you can expect on the actual exam. The questions do not attempt to cover more breadth or depth than the exam however, they are designed to make sure that you retain the material. Rather than allowing you to derive the answer from clues hidden inside the question itself, these questions challenge your understanding and recall of the subject. Questions from the Do I Know This Already quiz are repeated here to ensure that you have mastered the...

QoS and Traffic Mechanisms Summary

A host uses the RSVP protocol to request specific qualities of service from the network for particular application data streams or flows. MPLS fuses the intelligence of Layer-3 routing protocols with the speed of Layer-2 switching protocols. MPLS provides methods to perform traffic engineering, to guarantee bandwidth, and to further enable Virtual Private Networks (VPNs). GTS reduces outbound traffic flow to avoid congestion by constraining specified traffic to a particular bit rate. It is...

Redistribution

The redistribution between routing protocols must be configured carefully to prevent routing loops. Access lists, distribution lists, and route maps can affect redistribute routes these methods specify (select) routes for redistribution, for setting metrics, or for setting other policies to the routes. When redistributing routes into RIP, IGRP, and EIGRP, you must also configure the metric of the redistributed routes. The metric can be configured in the redistribution statement or a default...

References Used

The following resources were used to create this chapter Routing TCP IP, Volume I, Jeff Doyle, Cisco Press, 1998 CCDA Exam Certification Guide, Anthony Bruno and Jacqueline Kim, Cisco Press, 2000 RFC 1058, Routing Information Protocol, C.L. Hedrick RFC 2453, RIP Version 2, G. Malkin

Ring Resiliency

DPT uses Intelligent Protection Switching (IPS), which uses SRP control packets to proactively monitor ring performance to perform fault isolation and to provide self-healing rings by wrapping around outages within 50 ms. If multiple events occur concurrently, IPS uses event hierarchy rules to determine which events to handle and which events to handle first. IPS is multilayer aware. It monitors and handles events at Layers 1, 2, and 3 instead of just Layer 1. An event that occurs at Layer 3 is...

RIPv2 Message Format

The RIPv2 message format takes advantage of the unused fields in the RIPv1 message format by adding subnet masks and other information. Figure 7-3 shows the RIPv2 message format. 1 2 3 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 IP address (2nd route entry - up to 25) The following is a description of each field The following is a description of each field Command Indicates whether the packet is a request or a response message. The request message asks that a router send all or part of its...

RIPvl Configuration

The configuration for Router9 is shown in Example 7-3. Example 7-3 Configuration of Router9 interface Ethernet0 ip address 172.16.1.1 interface Serial0 ip address 172.16.4.1 The configuration for RouterlO is shown in Example 7-4. Example 7-4 Configuration of Router10 interface Ethernet0 ip address 172.16.2.1 interface Serial0 ip address 172.16.4.2 The configuration for Router8 is shown in Example 7-5. Example 7-5 Configuration of Router8 After the routers are configured, you can verify the RIP...

Route Reflectors

Network administrators can use route reflectors to reduce the number of required mesh links between iBGP peers. Some routers are selected to become the route reflectors to serve several other routers that act as clients. Route reflectors allow a router to advertise or reflect routes to clients. The route reflector and its clients form a cluster. All client routers in the cluster peer with the route reflectors within the cluster. The route reflectors also peer with all other route reflectors in...

Route Tagging

Routes can be configured with an administrative tag that identifies their origination. Routes originated from one external source can be set with a tag of 1, and routes from another external source can be set with a tag of 2. This is useful in identifying routes to be filtered when redistributing into other networks. The tag can be matched during redistribution. OSPF, RIPv2, and EIGRP carry tags on external routes. The tag can set policy on routes redistributed into BGP. Also, static routes can...

Router CLI

Example 3-12 Some Options of the show Command Accounting data for active sessions display information about flash file system Example 3-12 Some Options of the show Command (Continued) Frame-Relay information Interface status and configuration IP information Show the contents of logging buffers Current operating configuration Spanning tree topology Hot standby protocol information Contents of startup configuration The show ip keywords command is one of the most common options. Example 3-13...

Routers and Layer3 Switches

Routers operate in the network layer of the OSI model. They make forwarding decisions based on network layer addresses (e.g., an IP address). Figure 2-7 shows that routers define both collision (bandwidth) and broadcast domains. Each router interface is a separate broadcast domain that is defined by a separate sub-network. Routers are protocol aware, which means that they are capable of forwarding packets of routable protocols such as IP, IPX, DECnet, and AppleTalk. Figure 2-7 Routers Define...

Rsvp

For the written test, you must be familiar with RSVP, which is covered in this section. RSVP is one of the first significant protocols to set up end-to-end QoS over IP. RSVP is a signaling protocol that enables stations to obtain special qualities of service for their application data flows. RSVP reserves bandwidth for the network application. RSVP works in conjunction with routing protocols and installs the equivalent of dynamic access lists along the routes that routing protocols calculate....

Scenario

Answer the following questions based on Figure 2-11. Each question tests your knowledge of how different metrics affect the chosen route to a destination. Answers to these questions are in the Appendix, Answers to Quiz Questions. 1 A user performs a Telnet from PC 1 to PC 2. If the metric that the configured routing protocol uses is bandwidth, which route will the packets take 1 A user performs a Telnet from PC 1 to PC 2. If the metric that the configured routing protocol uses is bandwidth,...

Scenario 42

This scenario reviews your knowledge of DLSw. Knowledge of DLSw configuration and RIF construct in DLSw environment is essential for the CCIE written test. Use Figure 4-35 to answer the following questions. 1 What is the RIF from Host A to Host C With DLSw, the RIF terminates at the local virtual ring. Frame travels from ring 0x01b, bridge 0x9, and ring 21 (0x015). 2 What is the RIF from Host A to Host B With DLSw, the RIF terminates at the local virtual ring. Frame travels from ring 0x01b,...

Scenario 82

Use the following router command output to answer the scenario questions Router9> show clns is-neighbors d. Not enough information is given. Answer b The DIS's system name is concatenated with the circuit ID to form the pseudonode name on multiaccess networks. 2 What is the IS-IS interface priority on Router 8 d. Not enough information is given. Answer d The priority shown in the show clns is-neighbors command on the line showing Router 8 is that of Router 9, the router on which the command...

Scenarios 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 2 What is the RIF from Host A to Host B 3 What is the correct configuration for Router A source-bridge remote-peer 21 tcp 1.1.1.1 source-bridge remote-peer 21 tcp 2.2.2.2 source-bridge remote-peer 21 tcp 3.3.3.3 interface loopback 0 ip address...