Access List Basics

An access list is a sequential series of filters. Each filter comprises some sort of matching criteria and an action. The action is always either permitor deny. The matching criteria may be as simple as a source address alternatively, they may be a more complex combination of source and destination addresses, protocol type, ports or sockets, and specifications of the state of certain flags, such as the TCP ACK bit. A packet is dropped into the top of the stack of filters (Figure B.2). At each...

Access List Monitoring and Accounting

It is useful to be able to examine an access list, or even all access lists, without having to display the entire router configuration file. The command show ip access-list displays an abbreviated syntax of all IP access lists on the router. If a specific access list is to be observed, the list may be specified by name or number (Figure B.15). If you leave off the ip keyword (show access-list), all access lists will be displayed. Figure B.15. The show ip access-list command displays an...

Access List Types

The actual configuration lines for the access list shown graphically on the right of ,Figure B.4 are access-list 9 deny 10.23.147.0 0.0.0.255 access-list 9 permit 10.0.0.0 0.255.255.255 Every filter layer of an access list is represented by one configuration line. The various components of an access list line are discussed shortly, but for now notice the number 9 in both lines. This number is the access list number, and it serves two purposes It links all the lines of this list together and...

Administrative distance

Notice that all static routes using subnet 10.1.20.0 are followed by a 50. This number specifies an administrative distance, which is a measure of preferability when duplicate paths to the same network are known, the router will prefer the path with the lower administrative distance. At first this idea sounds like a metric however, a metric specifies the preferability of a route, whereas an administrative distance specifies the preferability of the means by which the route was discovered. For...

Administrative Distances

The diversity of metrics presents another problem If a router is running more than one routing protocol and learns a route to the same destination from each of the protocols, which route should be selected Each protocol uses its own metric scheme to define the best route. Comparing routes with different metrics, such as cost and hop count, is like comparing apples and oranges. The answer to the problem is administrative distances. Just as metrics are assigned to routes so that the most...

Appendix A Tutorial Working with Binary and

The best way to gain an understanding of binary and hexadecimal numbering is to begin by examining the decimal numbering system. The decimal system is a base 10 numbering system (the root deci means ten). Base 10means that there are 10 digits with which to represent numbers 0through 9. Most likely, we work in base 10 because our ancient ancestors began counting their cattle and children and enemies on their fingers (in fact, the word digit means finger). The use of place values allows the...

Appendix B Tutorial Access Lists

Access lists are probably misnamed these days. As the name implies, the original intention of an access list was to permit or deny access of packets into, out of, or through a router. Access lists have become powerful tools for controlling the behavior of packets and frames. Their use falls into three categories (Figure B.1) Security filters protect the integrity of the router and the networks to which it is passing traffic. Typically, a security filter permits the passage of a few,...

Appendix F Solutions to Troubleshooting Exercises

Chapter 2 Chapter 3 Chapter 5 Chapter 6 Chapter 7 Chapter 8 Chapter 9 Chapter 10 Chapter 11 Chapter 13 Chapter 14 1 For the following host addresses and subnet masks, find what subnet each address belongs to, the broadcast address of that subnet, and the range of host addresses for that subnet 2 You have been told to configure 192.168.13.175 on an interface with a mask of 255.255.255.240. Is there a problem If so, what is it A 192.168.13.175 28 is the broadcast address of subnet 192.168.13.160...

Area Addresses CLV

The Area Addresses CLV (Figure 10.21) is used to advertise the area addresses configured on the originating router. As the multiple Address Length Area Address fields imply, a router can be configured with multiple area addresses. There will never be more than three Address Length Area Address fields in PDUs originated by Cisco routers because that is the maximum number of area addresses supported. Figure 10.21. The Area Addresses CLV. Figure 10.21. The Area Addresses CLV. Figure 10.22 shows...

Authentication Information CLV

The Authentication Information CLV (Figure 10.26) is used when authentication is configured. The Authentication Type field contains a number between 0 and 255 that specifies the type of authentication used and hence the type of information contained in the Authentication Value field. The only authentication type currently defined by ISO 10589 or supported by Cisco is a cleartext password, which is Authentication Type 1. Figure 10.26. The Authentication Information CLV. Figure 10.26. The...

Been translated into type 5 LSAs by Goya 192168503

Type 7 AS External Link Stales (Area 192.166.10,O) Type 7 AS External Link Stales (Area 192.166.10,O) Several configuration options are available for the ABR. First, the no-summary option can be used with the area nssa command to block the flooding of type 3 and type 4 LSAs into the NSSA. To turn area 192.168.10.0 into a somewhat schizophrenically named totally stubby not-so-stubby area, Goya's configuration would be router ospf 30 network 192.168.20.0 0.0.0.3 area 0 network 192.168.10.0...

Better match of host cs address than is the first route

CjriS C coniwctetl, Static, T iCflP, 4 HIP, H Otile. EL JP U ElOUP, .X EIQRR r ernal r OSPF, ft C l inter rea E1 S f externa. ly c 1. E2 o-S f external tyf 2. L SP i iS-iS. L1 IS'IS level 1,1 IS-IS teuel 2, cand ate default u par-user star it runic iir .-.- y c 1 l it re urt l 175.19-35-1 is network B-.U.Si.U 172.1 f-. n. S) -li i , variably s jl> nt 11 ml , IB subnets, a rusks R 172.19.35.128 27 i 120 11 via 172.19.35.3, M & 0 r. Llht m'l F 172.19.35.16fl 27 126 11 via 172,13.35.3, M SU...

Bicycles with Motors

One of the difficulties of decentralized computing is that it isolates users from one another and from the data and applications they may need to use in common. When a file is created, how is it shared with Tom, Dick, and Harriet down the hall The early solution to this was the storied SneakerNet Put the file on floppy disks and hand carry them to the necessary destinations. But what happens when Tom, Dick, and Harriet modify their copies of the file How does one ensure that all information in...

C iM 16 0LwptmckD

15a 10 jn.-.i > i hi* 1 ip route 10.1.30.0 255.255.255.0 10.1.10.2 ip route 10.1.10.0 255.255.255.0 192.168.1.194 ip route 192.168.1.192 255.255.255.224 192.168.1. If Pooh needs to send a packet to host 10.1.30.25, it will look into its route table and find that the subnet is reachable via 10.1.10.2. Because that address is not on a directly connected network, Pooh must again consult the table to find that network 10.1.10.0 is reachable via 192.168.1.194. That subnet is also not directly...

Case Study A Basic Eigrp Configuration

Like IGRP, EIGRP requires only two steps to begin the routing process 1. Enable EIGRP with the command router eigrp process-id. 2. Specify each major network on which to run EIGRP with the network command. The process ID may be any number between 1 and 65535 (0 is not allowed), and it may be arbitrarily chosen by the network administrator, as long as it is the same for all EIGRP processes in all routers that must share information. Alternatively, the number may be an InterNIC-assigned...

Case Study A Basic IGRP Configuration

Only two steps are necessary to configure IGRP 1. Enable IGRP with the command router igrp process-id. 2. Specify each major network on which to run IGRP with the network command. The process ID is carried in the 16-bit autonomous system field of the update packet. The selection of a process ID is arbitrary any number between 1 and 65,535 (0 is not allowed) can be used, as long as it is used consistently on all routers that must share information via that particular IGRP process. Figure 6.11...

Case Study A Basic OSPF Configuration

The three steps necessary to begin a basic OSPF process are 1. Determine the area to which each router interface will be attached. 2. Enable OSPF with the command router ospfprocess-id. 3. Specify the interfaces on which to run OSPF, and their areas, with the network area command. Unlike the process ID associated with IGRP and EIGRP, the OSPF process ID is not an autonomous system number. The process ID can be any positive integer and has no significance outside the router on which it is...

Case Study A Basic RIP Configuration

Only two steps are necessary to configure RIP 1. Enable RIP with the command router rip. 2. Specify each major network on which to run RIP with the net work command. Figure 5.8 shows a four-router internetwork, with four major network numbers. Router Goober is attached to two subnets of network 172.17.0.0. The commands necessary to enable RIP are Figure 5.8. Both Andy and Barney are border routers between class-level networks. Figure 5.8. Both Andy and Barney are border routers between...

Case Study A Basic RIPv2 Configuration

By default, a RIP process configured on a Cisco router sends only RIPvl messages but listens to both RIPvl and RIPv2. This default is changed with the version command, as in the following example network 172.25.0.0 network 192.168.50.0 In this mode, the router sends and receives only RIPv2 messages. Likewise, the router can be configured to send and receive only RIPvl messages network 172.25.0.0 network 192.168.50.0 The default behavior can be restored by entering the c ommand no version in...

Case Study A Missing Neighbor

Figure 8.45 shows a small EIGRP internetwork. Users are complaining that subnet 192.168.16.224 28 is unreachable. An examination of the route tables reveals that something is wrong at router Grissom (Figure 8.46). 17 17 When troubleshooting an internetwork, it is a good practice to verify that the addresses of all router interfaces belong to the correct subnet. Figure 8.45. Subnet 192.168.16.224 28 is not reachable through Grissom in this example of an EIGRP Figure 8.45. Subnet 192.168.16.224...

Case Study A Protocol Migration

The distance command, when used without any optional parameters, specifies the administrative distance to be assigned to routes learned from a particular routing protocol. On first consideration, this action may not seem to be a route filtering function, but it is. When multiple routing protocols are running, routes are accepted or rejected based on their administrative distances. The internetwork in Figure 13.7 is running RIP, and there is a plan to convert to EIGRP. Several methods exist for...

Case Study Address Aggregation

A new router is added to the internetwork in Figure 8.43. The five network addresses that Earhart must advertise to Yeager can be summarized with two aggregate addresses. Earhart's configuration will be Figure 8.43. Earhart is advertising two aggregate addresses to Yeager. Figure 8.43. Earhart is advertising two aggregate addresses to Yeager. interface Ethernet1 ip address 10.15.15.254 255.255.255.252 ip summary-address eigrp 15 172.0.0.0 255.0.0.0 ip summary-address eigrp 15 192.168.16.0...

Case Study Authentication

Cisco's implementation of RIPv2 message authentication includes the choice of simple password or MD5 authentication, and the option of defining multiple keys, or passwords, on a key chain. The router may then be configured to use different keys at different times. The steps for setting up RIPv2 authentication follow. 1. Define a key chain with a name. 2. Define the key or keys on the key chain. 3. Enable authentication on an interface and specify the key chain to be used. 4. Specify whether the...

Case Study Configuring OnDemand Routing

ODR is enabled with a single command, router odr. No networks or other parameters must be specified. CDP is enabled by default it needs to be enabled only if it has been turned off for some reason. The command to enable the CDP process on a router is cdp run to enable CDP on a specific interface, the command is cdp enable. Figure 12.17 shows a typical hub-and-spoke topology. To configure ODR, the hub router will have the router odr command. As long as all routers are running IOS 11.2 or later...

Case Study Configuring Unicast Updates

Next, router Bea is added to the Ethernet link that Andy and Floyd share (Figure 5.11). The no-RIP policy between Andy and Floyd remains in place, but now Bea and Andy, as well as Bea and Floyd, must exchange RIP advertisements. Figure 5.11. No RIP updates should be exchanged between Andy and Floyd, but both should exchange Figure 5.11. No RIP updates should be exchanged between Andy and Floyd, but both should exchange The configuration of Bea is straightforward network 192.168.12.0 network...

Case Study Disabling Automatic Summarization

By default, EIGRP summarizes at network boundaries as do the protocols covered in previous chapters. Unlike those protocols, however, EIGRP's automatic summarization can be disabled. Figure 8.42 shows a situation in which disabling summarization is useful. Figure 8.42. Disabling automatic summarization at Cochran and Lindbergh prevents ambiguous routing to Figure 8.42. Disabling automatic summarization at Cochran and Lindbergh prevents ambiguous routing to New Ethernet links have been added to...

Case Study Discontiguous Subnets

In Figure 5.13, another router has been added to the internetwork with a subnet 10.33.32.0 20 on its El interface. The problem is that the other subnet of network 10.0.0.0, 10.33.0.0 20, is connected to Barney, and the only route between the subnets is via 192.168.83.0 and 192.168.12.0 two entirely different networks. As a result, network 10.0.0.0 is discontiguous. Figure 5.13. Classful protocols such as RIP and IGRP cannot route a topology in which the subnets of network 10.0.0.0 are separated...

Case Study Filtering Specific Routes

Figure 13.2 shows a portion of an internetwork running RIPv2. Barkis is providing connectivity to the rest of the internet via Traddles. In addition to the 700 specific routes within BigNet, Traddles is advertising a default route to Barkis. Because of the default route, Barkis, Micawber, Peggotty, and Heep do not need to know the other 700 routes in BigNet. So the objective is to configure a filter at Barkis that will accept only the default route from Traddles and reject all other routes....

Case Study Integrated ISIS on NBMA Networks

Figure 10.64 shows four routers running IS-IS connected by a partially meshed Frame Relay network. The IP addresses, DLCIs, and NETs are shown. The IS-IS configurations of all routers have been verified as correct, and no authentication is configured. Figure 10.64. IS-IS is not establishing adjacencies across the Frame Relay network. Figure 10.64. IS-IS is not establishing adjacencies across the Frame Relay network. The problem with this internetwork is that no routes are being discovered...

Case Study Manipulating RIP Metrics

A serial link, to be used as a backup, has been added between Ernest_T and Barney (Figure 5.16). This link should be used only if the route via Andy fails. The problem is that the path between Barney's 10.33.0.0 subnet and Ernest_T's 10.33.32.0 subnet is 1 hop via the serial link and 2 hops via the preferred Ethernet links. Under normal circumstances, RIP will choose the serial link. Figure 5.16. RIP metrics must be manipulated so that the 2-hop Ethernet route between Barney and Ernest_T will...

Case Study Misconfigured Summarization

Figure 9.102 shows a backbone area and three attached areas. To reduce the size of the link state database and to increase the stability of the internetwork, summarization will be used between areas. Figure 9.102. The summary addresses shown for each area will be advertised into area 0. Area 0 will also Figure 9.102. The summary addresses shown for each area will be advertised into area 0. Area 0 will also The individual subnets of the three nonbackbone areas are summarized with the addresses...

Case Study Multiple IGRP Processes

Two new routers, Lovett and Harriman, have been added to the internetwork (Figure 6.18). A decision has been made to create two IGRP autonomous system domains in the internetwork with no communications between the two. Figure 6.19 shows the two autonomous systems and the related links for each. Figure 6.18. Separate routing domains are to be created in this internetwork. Figure 6.18. Separate routing domains are to be created in this internetwork. Figure 6.19. The routers Harriman and Acheson...

Case Study Multiple Redistribution Points

Figure 13.12 shows an internetwork very similar to the one depicted in Figure 11.3. Recall from the associated discussion in Chapter 11 that the problem with multiple redistribution points is that administrative distances can cause routers to choose undesirable paths. In some cases, route loops and black holes can result. For example, Bumble's routing table (Figure 13.13) shows that it is routing to network 192.168.6.0 through Blathers, rather than using the preferable route through Monks....

Case Study OSPF and Secondary Addresses

Two rules are related to the use of secondary addresses in an OSPF environment 1. OSPF will advertise a secondary network or subnet only if it is also running on the primary network or subnet. 2. OSPF sees secondary networks as stub networks (networks on which there are no OSPF neighbors) and therefore will not send Hellos on them. Consequently, no adjacencies can be established on secondary networks. Figure 9.65 shows the DNS server and an additional router attached to the E0 interface of...

Case Study OSPF over Demand Circuits

OSPF over demand circuits is easily configured by adding the command ip ospf demand-circuit to the interface connected to the demand circuit. Only one end of a point-to-point circuit, or the multipoint side of a point-to-multipoint circuit, needs to be declared a demand circuit. In most cases, OSPF over demand circuits should not be implemented across a broadcast medium. On such a network, the Hello packets cannot be suppressed, and the link will stay up. If the virtual circuits in Figure 9.92...

Case Study Passive Interfaces

The router Floyd has been added to the internetwork (Figure 5.10). It is desired that no RIP advertisements be exchanged between Floyd and Andy. This is easy enough at Floyd Figure 5.10. Network policy calls for no RIP exchanges between Andy and Floyd. Figure 5.10. Network policy calls for no RIP exchanges between Andy and Floyd. Floyd(config-router) network 192.168.100.0 By not including a network statement for 192.168.12.0, Floyd will not advertise on interface 192.168.12.66. Andy, however,...

Case Study Redistributing EIGRP and OSPF

The internetwork of Figure 11.19 has an OSPF domain and two EIGRP domains. Router Hodges is running OSPF process 1. Podres is running EIGRP process 1, and EIGRP process 2 is running on Snider and Campanella. Robinson has the following configuration Figure 11.19. Hodges is running OSPF, and Podres is running EIGRP 1. Snider and Campanella are running Figure 11.19. Hodges is running OSPF, and Podres is running EIGRP 1. Snider and Campanella are running router eigrp 1 redistribute ospf 1 metric...

Case Study Redistributing ISIS and RIP

In the internetwork of Figure 11.30, Aaron is running IS-IS, Williams is running RIPv1, and Mays is redistributing. Mays' IS-IS configuration is Figure 11.30. Router Mays is redistributing RIP into IS-IS and IS-IS into RIP. Figure 11.30. Router Mays is redistributing RIP into IS-IS and IS-IS into RIP. redistribute rip metric 0 metric-type internal level-2 net 01.0001.0000.0c76.5432.00 redistribute rip metric 0 metric-type internal level-2 net 01.0001.0000.0c76.5432.00 router rip redistribute...

Case Study Redistribution with IGRP

Redistribution between routing protocols is covered in Chapter 11, but it is worth noting here that if an IGRP process and an EIGRP process have the same process IDs, they will redistribute automatically. In Figure 8.38, router Curtiss has the following configuration Figure 8.38. If Earhart is configured with both EIGRP and with IGRP, using the same process ID for both, route information will be redistributed. Figure 8.38. If Earhart is configured with both EIGRP and with IGRP, using the same...

Case Study Route Summarization

Route summarization between areas in a link state protocol is introduced in Chapter 9. A more complete discussion of summarization, in the context of default routes, is presented in Chapter 12. Briefly, summary routes are useful because They reduce the size of LSPs, which reduces the size of the link state database consequently, memory and CPU are conserved. They hide instabilities within areas. If an address within a summary range changes or a link changes state, the change is not advertised...

Case Study Setting Maximum Paths

The maximum number of routes over which IGRP can load balance is set with the maximum-paths paths command. Paths may be any number from one to six in IOS 11.0 and later and any number from one to four in earlier versions. The default for all versions is four. Figure 6.16 shows three parallel paths of varying costs from McCloy to network 172.18.0.0. The network administrator wants to load balance over a maximum of only two of these routes while ensuring that if either of these paths should fail,...

Case Study Setting Router IDs with Loopback Interfaces

Suppose router Matisse from Figure 9.61 has been configured in a staging center and then sent to the field to be installed. During the bootup, the router reports that it cannot allocate a Router ID, and it seems to report the network area commands as configuration errors (Figure 9.63). Worse, the OSPF commands are no longer in the running configuration. Figure 9.63. OSPF will not boot if it cannot find an active IP address for its Router ID. Cisco internetwork Operating 5iys or Software I OS it...

Case Study Stub Areas

Because no type 5 LSAs are being originated within area 1, it can be configured as a stub area. Note that when an attached area is configured as a stub area, the Hellos originated by the router into that area will have E 0 in the Options field. Any router receiving these Hellos, which is not similarly configured, will drop the packets, and an adjacency will not be established. If there is an existing adjacency, it will be broken. Consequently, if an operational area is going to be reconfigured...

Case Study Unequal Cost Load Balancing

Given up to six parallel routes of equal cost, 5 IGRP will do equal-cost load balancing under the same fast process switching constraints as RIP. Unlike RIP, IGRP can also perform unequal-cost load balancing. An additional serial link has been added between Acheson and Kennan in Figure 6.12, with a configured bandwidth of 256K. The goal is to have Acheson perform unequal-cost load balancing across these two links-spreading the traffic load inversely proportional to the metrics of the link. 5...

Case Study Unequal Cost Load Balancing Again

The entire internetwork of Figure 6.20 is routed with a single IGRP process, and the bandwidths for the serial links are configured to the numbers shown. Default delays are used. Notice that the addresses of the link between Lovett and Harriman are different from the previous examples. Because network 10.0.0.0 can be reached from Acheson not only by the two serial links but also via the Ethernet to Lovett, the network administrator wants to distribute the traffic proportionately among all three...

Case Study Using VLSM

Referring again to Figure 7.10, the subnet 172.25.150.0 24 has been assigned to the internet shown. That subnet has been further subnetted to fit the various data links by expanding the mask to 28 bits the available sub-subnets, in binary and dotted decimal, are shown in Figure 7.13. Each of the subnets1101 will have, according to the 2n - 2 formula, 14 host addresses. Out of these, 172.25.150.32, 172.25.150.192, and 172.25.150.224 have been used. 101 Now that the concept should be firmly in...

Case Study Virtual Links

Figure 9.89 shows an internetwork with a poorly designed backbone area. If the link between routers Hokusai and Hiroshige fails, the backbone will be partitioned. As a result, routers Sesshiu and Okyo will be unable to communicate with each other. If these two routers are ABRs to separate areas, inter-area traffic between those areas will also be blocked. Figure 9.89. A failure of the link between Hokusai and Hiroshige will partition the backbone area. Figure 9.89. A failure of the link between...

Basic Concepts Internetworks Routers and Addresses

Once upon a time, computing power and data storage were centralized. Mainframes were locked away in climate-controlled, highly secure rooms, watched over by a priesthood of IS administrators. Contact with a computer was typically accomplished by bringing a stack of Hollerith cards to the priests, who interceded on our behalf with the Big Kahuna. The advent of the minicomputer took the computers out of the IS temple of corporations and universities and brought them to the departmental level. For...

Route Redistribution

Principles of Redistribution Redistributing from Classless to Classful Protocols Case Study Redistributing IGRP and RIP Case Study Redistributing EIGRP and OSPF Case Study Redistribution and Route Summarization Case Study Redistributing IS-IS and RIP Case Study Redistributing Static Routes A router performs redistribution when it uses a routing protocol to advertise routes that were learned by some other means. Those other means may be another routing protocol, static routes, or a direct...

Chapter

1 What are the five layers of the TCP IP protocol suite What is the purpose of each layer A The five layers of the TCP IP protocol suite are the following The physical layer contains the protocols of the physical medium. The data link layer contains the protocols that control the physical layer How the medium is accessed and shared, how devices on the medium are identified, and how data is framed before being transmitted on the medium. The internet layercontains the protocols that define the...

TCPIP Review

The purpose of this chapter is to examine the details of the protocols that enable, control, or contribute to the routing of TCP IP, not to do an in-depth study of the TCP IP protocol suite. Several books on the recommended reading list at the end of the chapter cover the subject in depth. Read at least one. Conceived in the early 1970s by Vint Cerf and Bob Kahn, TCP IP and its layered protocol architecture predates the ISO's OSI reference model. A brief review of TCP IP's layers will be useful...

1

A Subnet 192.168.1.64 27 will no longer be reachable from Piglet. Subnets 10.4.6.0 24 and 10.4.7.0 24 are also no longer reachable from Piglet. 2 The static route configurations for the routers in 3 shows another internetwork in which users are complaining of connectivity problems. A The mistakes are RTC The route to 10.5.8.0 24 points to the wrong next-hop address. RTC The route to 10.1.1.0 24 should be 10.5.1.0 24. RTC There is no route to 10.5.4.0 24. RTD The route to 10.4.5.0 24 should be...

Static Routing

An important observation from Chapter 2, TCP IP Review, is that the data link physical layers and the transport network layers, as defined by the OSI model, perform very similar duties They provide the means for conveying data from a source to a destination across some path. The difference is that the data link physical layers provide communications across a physical path, whereas the transport network layers provide communications across a logical or virtual path made up of a series of data...

Classful Routing Directly Connected Subnets

Classful route lookups can be illustrated with three examples (referring to Figure 5.5) 1. If a packet with a destination address of 192.168.35.3 enters this router, no match for network 192.168.35.0 is found in the routing table and the packet is dropped. 2. If a packet with a destination address of 172.25.33.89 enters the router, a match is made to class B network 172.25.0.0 24. The subnets listed for this network are then examined no match can be made for subnet 172.25.33.0, so that packet,...

CLV Fields

The variable-length fields following the PDU-specific fields are Code Length Value(CLV)m triplets, as shown in Figure 10.17. The Code is a number specifying the information content of the value field, the Length specifies the length of the Value field, and the Value field is the information itself. As the one-octet size of the Length field implies, the maximum size of the Value field is 255 octets. 17 The acronym CLV is not used in ISO 10589, but is used here for convenience. You are already...

Configuration Exercises

1 Configure static routes for each router of the internetwork shown in Figure 3.25. Write the routes so that every subnet of the internet has an individual entry. Figure 3.25. The internetwork for Configuration Exercises 1 and 2. Figure 3.25. The internetwork for Configuration Exercises 1 and 2. Rewrite the static routes created in Configuration Exercise 1 to use the minimum possible route entries 7 . (Hint RTA will have only two static route entries.) 7 If this exercise is being implemented in...

Configuring IGRP

Although a few more configuration options are available to IGRP than to RIP, the basic configuration is every bit as simple The router command is used to establish the routing process, and the networkcommand is used to specify each network on which IGRP is to run. As with RIP, only major network numbers can be specified because IGRP is also a classful protocol. The commands neighbor, for sending unicast updates, and passive-interface, for preventing updates from being broadcast on selected...

Configuring Route Maps

Like access lists (see Appendix B,Tutorial Access Lists), route maps by themselves affect nothing they must be called by some command. The command will be either a policy routing command or a redistribution command. Policy routing will send packets to the route map, whereas redistribution will send routes to the route map. The case studies in this section demonstrate the use of route maps for both redistribution and policy routing. Route maps are identified by a name. For example, the following...

Counting to Infinity

Split horizon will break loops between neighbors, but it will not stop loops in a network such as the one in Figure 4.6. Again, 10.1.5.0 has failed. Router D sends the appropriate updates to its neighbors router C (the dashed arrows) and router B (the solid arrows). Router B marks the route via D as unreachable, but router A is advertising a next-best path to 10.1.5.0, which is 3 hops away. B posts that route in its route table. Figure 4.6. Split horizon will not prevent routing loops here....

Crossing two serial links and a Token Ring

Codes c connected, 5 static, - io . r - ftlP, '-1 mobile, B Q EICTP. EX - EiGflP external, o - OSPF, 1A 33 inter iirsii Ml - OSPF animal Type 1 , MJ - OSPF k SA mortal type 2 * OEPF external tyi t, 2 oxternal tyt 2. i. - E.rl i is-15, - rs-is level--, _5 - IS-is i& vei-2, - - candidate uyfLi.it U par.user static r ute, u QW R 19 . 168.1 .tt 24 1120 1 j via 192.133.2.1, eS O 0C. Ethernet G 19 . 165.2. 9 2* iu ili't-tly c nii- t it . - r-0 c ie ,i69,3r 2* is directly connected, saris 0...

Data Link Addresses

In a certain community in Colorado, two individuals are named Jeff Doyle. One Jeff Doyle frequently receives telephone calls for the person with whom he shares a name so much so that his clever wife has posted the correct number next to the phone to redirect errant callers to their desired destination. In other words, because two individuals cannot be uniquely identified, data is occasionally delivered incorrectly and a process must be implemented to correct the error. Among family, friends,...

Delivering them to the correct destination

Tracing the rc-.jlc ta .72 .16.23 .75 lype escape sequence la aucr-t. Tracing the rc-.jlc ta .72 .16.23 .75 The suspicious aspect of all of this is that Kanga should not be routing the packet, which appears to be the case. Kanga should recognize that the destination address of the packet is for its directly connected network 172.16.20.0 and should be using the data link to deliver the packet to the host. Therefore, suspicion should fall on the data link. Just as...

Designated Router DR

To prevent these problems a Designated Router is elected on multi-access networks. The DR has the following duties To represent the multi-access network and its attached routers to the rest of the internetwork To manage the flooding process on the multi-access network The concept behind the DR is that the network itself is considered a pseudonode, or a virtual router. Each router on the network forms an adjacency with the DR (Figure 9.3), which represents the pseudonode. Only the DR will send...

Designated Routers

IS-IS elects a Designated Router (or more officially, a Designated IS) on broadcast multi-access networks for the same reason OSPF does. Rather than having each router connected to the LAN advertise an adjacency with every other router on the network, the network itself is considered a router a pseudonode. Each router, including the Designated Router, advertises a single link to the pseudonode. The DR also advertises, as the representative of the pseudonode, a link to all of the attached...

Designated Routers and Backup Designated Routers

Multiaccess networks present two problems for OSPF, relating to the flooding of LSAs (described in a later section) 1. The formation of an adjacency between every attached router would create many unnecessary LSAs. If n is the number of routers on a multiaccess network, there would be n(n- 1) 2 adjacencies (Figure 9.2). Each router would flood n- 1 LSAs for its adjacent neighbors, plus one LSA for the network, resulting in n 2 LSAs originating from the network. Figure 9-2. Ten adjacencies would...

Diffusing Computation Example

This example focuses only on Cayley and its route to subnet 10.1.7.0. In Figure 8.13, the link between Cayley and Wright (10.1.1.1) has failed. EIGRP interprets the failure as a link with an infinite distance.1101 Cayley checks its topology table for a feasible successor to 10.1.7.0 and finds none (refer to Figure 8.6). 101 An infinite distance is indicated by a delay of 0xFFFFFFFF, or 4294967295. Figure 8.13. The link between Wright and Cayley has failed, and Cayley does not have a feasible...

Domain

TonriBCted, s ilnlio. 3FP, i R , W - imftlis, 0 tx rKSRP CUimjl, 0 - CSPf, 4 - OSPF i UtC 03FT external type 1 , E2 DliFF external tys ii 2. E EOF L IS LS l vfil L.I Si ft lDvtl -2, CiitdiflitD default list ri& or-t is li.i.i.J u.n.-n. d Jr.i.MS.i'i .0 iii SJJAettOd, 1 i.urr-frl f. .1.0 Li directly connected, ckeiinirrjO h.c if. vaf-iafti subdued, s-uftntts, s .h-.i 16.5.3 2'jj.2 -5.2SD.i 119 13BI Vin t72.l6,1,2h Oi ' r ifl.4,1 SS.iM.SSS.i ini rsi via i7S.it. 1.2, ii(i (ii ii. i& .r,.-...

Extended IP Access Lists

Extended IP access lists provide far more flexibility in the specification of what is to be filtered. The basic format of the extended IP access list line is access-list access-list-number deny permit protocol source source-wildcard destination destinationwildcard precedence precedence tostos log Some of the features here are familiar, and some are new. access-list-number, for extended IP access lists, is between 100 and 199. protocol is a new variable that looks for a match in the protocol...

Figure 1012 This route table shows both level 1 and level 2 ISIS routes

Codes C canr.i.cTad, 3 Tatio, IGF , R RJ P, 1 mobile, EJ LSG-p 0 LlOR . l < EIGftP external, 0 OS f , 3a oSh irttor area lt osr1 external i, L2 os i ext n i type a, l lgp 1 IS IS, Li IS IS ieveL 1, L2 IS IS level 2, * candidate default iG.U.fi.fi is variably susnellea, fi spoilers, 3 riaski iG.U.fi.fi is variably susnellea, fi spoilers, 3 riaski 2 > 5.255.2& .e LE dlr Ctlyl COflil tOil 255.25 -255-0 115 301 via lfl.1.3.2 255,25S. 55.0 115 20 vis n.n.fl.fj. J55 .255.255.5 LS dlrc tlv...

Figure 1031 The Intermediate System Neighbors CLV for LSPs

Virtual Flag, although eight bits long, has a value of either 0x01 or 0x00. A 0x01 in this field indicates that the link is a level 2 virtual link to repair an area partition. The field is relevant only to L2 routers that support area partition repair Cisco does not, so the field will always be 0x00 in Cisco-originated LSPs. R is a reserved bit and is always zero. I E, associated with each of the metrics, indicates whether the associated metric is internal or external. The bit has no meaning in...

Figure 1047 The L1 LSPs of London and Rome have ATT 1 indicating a connection to another area

IS IS Level 1 Link State Database LSPlii HSB0.aCBA.2AAS) . BB OW30.0CGA2C51 .0 a0ti0.0D0A.2C51.01 HSB0.JB )K. i75f> .aB The problem is that the ATT bit is a CLNS function, and the IP process cannot directly interpret the bit. There are two solutions to the problem. The first solution is to enable IS-IS for CLNS on the interfaces in addition to IS-IS for IP. For example, the serial interface configurations for London and Paris are ip address 10.1.255.6 255.255.255.252 ip router isis clns...

Figure 1050 The support of multiple area addresses per router eases area changes

Suppose that the powers that be over the internetwork in Figure 10.41 decree that the area addressing scheme being used is inappropriate and should become GOSIP compliant. After registering with the U.S. GSA, the following components are to be used to construct the NETs The new NETs are shown in Table 10.5. Table 10.5. The new GOSIP-format NETs to be assigned to the routers in Figure 10.41. The first step in changing the area addresses is to add the new NETs to the routers without changing the...

Figure 1058 This SPF log reveals instability in area 1 of Figure 1054

To further investigate instabilities revealed by the SPF log, three useful debug commands are available. Figures 10.59, 10.60, and 10.61 show output from these three debug functions. In each case, the debug messages show the results of disconnecting and reconnecting the serial interface of Zurich in Figure 10.54 from the perspective of Geneva. The first, debug isis spf-triggers (Figure 10.59), displays messages pertaining to events that trigger an SPF calculation. The second command is debug...

Figure 1061 debug isis spfstatistics displays statistical information about the SPF calculation

H r'L'vLI (ictl j(J LSI , My1 statistics is hp nrciLiio n.i-1 n Statistics data dflCugaing nn Slii .C a T. C'jrplHH t LI ShT, COaputis time H.BHH, LI n d -ij 2 links di Sll, Sis k-Nsr . Conpl tfl ll sf'f, Gonpute nnif b.aHU, a raits, 2 links jji spt. Within each area, every router must have an identical link state database. Additionally, every L1 L2 and L2 router in the IS-IS domain must have an identical L2 database. If you suspect that a router's link state database is not correctly...

Figure 1063 debug isis snppackets displays detailed information about CSNPs and PSNPs

IS IS CSNP Papackets debugging s on ISIS SUP HOC Li CSKV hum eaW. 7e.5B7C CEtlWfline) SN I C Nf r nn tj r Clflfla . SQHfi. Hi tffl. w M Li I J F . F M F . I F M . I I If ISIS SNP r Sana fill try Oe& O.SCfli 2C& 1 .M M. 6M 82 ISIS SnP s.irii entry capo.5E17C.z< 9 & a, seq A7 SIS SNP Sana antry Mee.eC7S.5B7C.02 M. seq 85 SNP fi& c l CSHP trnm UOR-ii. Sifii. 1E17C iSiS-SHP CSNP rafla HW.m.wee.eeee to ffff.ffff.ffff, if ISIS Sill Sana an try MM.i& CiiA. C& l .MO0, H2 Sup Entry...

Figure 1071 The ISIS neighbor table of router A Troubleshooting Exercise

Floutar afrsnni, l r- s is Fi 6 i l) n t 0 ivitilii raiL'.-i id inttrrace state O 0U.30E I .IXilU 100 Up ft 'pit A lcreSi(E ) 11 IP Addresses) 192.166,11,2 Uptime HBon.sMLi .-iEi s sea. i up Area Addresslas) fii JP Address(ea) Uptime 2B 22 Are Address IP Addr S (e6) 152. lUS.ti. 13 Uptime 1 29 45 atSOn.OBLI .1234 Sea. 15 Up Area Addresu(ai) Ci IP Address < os 1S2,H56,5.& Uptime 1 < H i5 Houtar Aff

Figure 1118 Ford is running IGRP and Berra is running RIP Mantle is performing redistribution

16.5.2.0.Of 24 jgj 10.6.2.0 24 router rip redistribute igrp 1 metric 5 passive-interface Ethernet1 network 10.0.0.0 default-metric 1000 100 255 1 1500 passive-interface Ethernet0 network 10.0.0.0 Both methods of assigning metrics are used here for demonstration purposes. In most cases, a redistribution scheme as simple as this will use one method or the other. Notice that Mantle is also connected to a stub network (192.168.10.0 24). In this case, the stub network should be advertised into the...

Figure 1133 Aarons routing table with a summary route to the subnets within the RIP domain

TOhncited, 3 - atatic, I - IGKP, K - P.IP, M - mobile, E - EGP IGP.P, - E & RP external, 0 - CSt , IA - OStf Hi - OS F HSSJL external type 1, 2 - G59F 31SSA external type 2 OSPP external typt 1, E2 - OSPP external type IS-IS, 11 - IS-IE level-1, L2 - IS-IS level-2, lO.O.O.D e IS Viiiiliiy Sidi flitted, I SLbheta, 2 iniialls 2,0.0 lfr 115 138 Yia 1Q.1,4,Z, BtheinetO 1.3.0 24 is directly connected, Ethernet4 1.1.0 24 is dir itly Connected, Ethernet 1.4.0 24 is directly n iected, EtbernetO...

Figure 1134 The routes with subnets other than 24 are not redistributed into the RIP domain

Codes C - connected, 5 - static, I - IGKP, R - RIP, M - mobile., D - EIGP.P, SK - EIGP external, - OSPF, IA - 3PF inter El - OSPF1 external type 1, Ei - CSPf external type i, E - 1 - IS-IS, Ll - IS-IS level-1, E2 - IS-IS level-2, * - candidate default P. 10.1.3.0 120 1) via 10.2.1,2, 00 03 01, EthernetO C 10.2, l.U is ij.rsctJ.y connected, EthernetC R 10.1.1.0 130 1 via 10.2.1.2, 00i00 02, EthernetD C 10.2,2-0 is directly connected, Ethernet I R 10.1,1,0 130 11 via 10.2,1.2, OO 0D O2, EthernetO...

Figure 1135 Subnets 101216028 and 101222428 have been summarized with the address 1012024

To(Je3i C - connected, 5 - stiit c, I - IGPP, El - RIP, M - mobile, B - EGP D - EIGP.P. SK - SIGP5 iKtern.sir O - OSPF. IA - GSP7 inter are Si - OSPF c-HtcEinU type J, E3 - cxtirraJL typt Z, S - E< Si 1 - IS-13, LI - IS-IS level-1, E2 - IS-IS level-1, * - CAiiditUte default V - per-uu i static Teilte 10.0,0,D 3 la subnettedf E subneta P. 10,1.3.0 120 1 via 10.2.1.2, 00 0 03. EtkerrtetO Hi HJ.l.Z.Q IliP 1 rifl 10,2-1. , no 01, Btheicnita C 10,2.1.0 la dlteolily tisisietlied, Etiieenecfl P...

Figure 1136 Mays considers the summary address 1012024 to be directly connected to Ethernet

Connected, S - static, 1 - IGP E , Ii - Elf, M - nwibile, S - BEE 2IGEP, EM - EIGRP external O - OSPE, TA - OSE F Intel ftECil Kiff HSSA external typ 1, HE - 0S P HS A external type 2 EPF elite Lnal type Ij E2 - CSE F external type 2, 3 - 2GP IS-IS, m - 5-I-S level-1, L - 3- IS level-1, * - candidate deiault 10.0. D. 8 is v iabiy submitted, a Subnet*, 2 maaSls I.3.0 4 115 20 via 10.1.4.1, EthernetO 1.3.0 24 is diiecHy connected Ethernet0 .1.D 4 ifl diifctiy coniiftterS, Ethernet 1 I.1.Q 4 115...

Figure 116 Soon after the reboot Gehrig is routing packets to 19216810 via Lazzeri

Codes t - connected, S - static, I - JGflfr R - RIP, M - raobiie, B - 6< SP D - EIGEP, EX - EICK xt e e nal, O - OSPF, IA - OSPF intes aiea tri - OSPF tfSSA external type ir NJ - OSff ISSA external type 2 El - OSPF sterna typ I r E2 - OSPF external type 2, E - E P i - 13-13, III - IS-IS level-I, L2 - 13-13 livel-I, * - candidate default (J - pec-user static coutc, o - I 15 .16S.1.0 H 100 ltlQSJ vi* 192.163.3.S, 0fl 0S 38, SeniilU C LSJrlcS. ,0 3t 3 directly connected, EthernetO C lS2.i 8.3 ,0...

Figure 129 The defaultnetwork command is used at Athens to generate a default network advertisement

Figure 12.10 shows that network 10.0.0.0 has been tagged as a candidate default route in Athens' routing table, but notice that no gateway of last resort is specified. The reason is that Athens is the gateway to the default network. The ip default-network command will cause Athens to advertise a default network, even though no network statement for 10.0.0.0 exists under the RIP configuration (Figure 12.11).

Figure 134 The filter at Traddles allows only the default route to be advertised to Barkis

RIP received v2 update from 192.16& .75.19 on Seriall RIP Sending v2 utJi to 22*.0.0.9 via Ethernet 192.168.75.33) 192.l68.75.fi4 27 > & .0.0.0, natric 2. tag 2 192.160.75.196 3B -> 8.0.0,0, metric tag 3 l -h2. 169. i 30 0.0.0.0, metric 1, tag B RIP sending v2 update to 22 . 0.0.9 via Serial (192.163.75,202) 2.160. fh.32.-2f > a.0.0.0, natric 1, tag C 192. 160.75.196 30 -> 0.0.0,0, metric 1t tag 2 192.160.75.204 30 -> 0.0.0,0, metric 27 tag 3 RIP sending v2 u n-.a to 25 .0.0.3...

Figure 139 After the RIP administrative distance is changed back to 120 the routes with a distance of 70 begin to age

God& s c - connected, s - static, i - igftp, r - hip, u - nodi b - ewp 0 Etonr, ex EIOPP external, 0 OSPF, IA CSf> r inter area M - external 1 ti2 - GS F lJ33A external typa 2 Ei . typa . 6 2 - OSPF external type 2, i 1 I3-ie. l1 IS- s leiral-l, - is-is lenel-2, * candidate default u - uyyi- -ullii, c - oor 2. is. is SUbftettad, 11 uuu'etu C 172.16.25 . is directly connected, Serial G 172.16.253,0 is Ji'eijtly cC iit iH iJ. Stfiial' ft 172.16.2S*. i7 i via 1 2. 1 0.2.25S. 00 02 31,...

Figure 142 Policy routing allows highpriority traffic from the Mongo System to be routed over the FDDI link while

Table 14.1 and table 14.2 show the match and set commands that can be used with redistribution, and table 14.3 and table 14.4 show the match and set commands that can be used with policy routing. Table 14.1. Match commands that can be used with redistribution. Table 14.1. Match commands that can be used with redistribution. match interface type number type number Matches routes that have their next hop out one of the interfaces specified. match ip address access-list-number name...

Figure 146 FTP packets TCP ports 20 and 21 are being forwarded to Lucy whereas Telnet packets TCP port 23 with the same

& chreeder < jet)uq ip packet < m t . > l j 10 P packet ik-tjuyyiiKj is en uit '. iiii< iJ.i for a tn ii t iu & chreeder < jet)uq ip packet < m t . > l j 10 P packet ik-tjuyyiiKj is en uit '. iiii< iJ.i for a tn ii t iu The purpose of segregating bulk and interactive traffic, as demonstrated in the last example, is so that the small packets characteristic of interactive traffic do not become delayed by the large packets characteristic of bulk traffic. The problem with the...

Figure 316 10151 matches the entry for 1010016 and will be forwarded to 10461

Codes c cMiiact& tfj a static, i i ip, Ft flip, t maulle, u l gp u - EiGhp, lx liuup external, y uspf , 1a OSPf inter area lt osPI external type t O-SHi eternal i2, L lap l It I . Ll IS IS level 1, L2 IS 13 level 2. - candidalc default I , , . lk variably subnetteO, 3 sublets, 2 *asKs C 10.4,6.0 255.255.255.0 LS dir& Ctly CCllrttCLCD. Si-TLail t is directly connected, Ethernet 193.138.1.0 255.255.255.22* is submitted, 1 subnets Figure 3.17 shows Tigger's route table. The destination...

Figure 317 10151 matches the entry for 1010016 and will be forwarded to 1921681194

Ce-iies C connected, s-isilc. 1 i Rr1, F H.l , U stabile, Ei H P eiGBP, ix EIGRP external, 0 QSPF, IA Q& PF inter area L1 USPF- -iT .'i-nal ype- 1, L2 SPF- external type 2. I - ESP i IS IS, Li IS IS Level 1, lx is is Jevd , ' candidate default is.0.0.a is viii-Lably su& ih i let , 3 suone-ls. 2 maiki C X55,255,0 ls directly connected, Seriall 192.166,1.0 255.255.255,224 Li Subletted, 3 SuBrl lfi C i9z.iflfl.i,64 is direcily o inec inn . Serial C 19z.ififl.l. 19z ls directly connc tnd. 6th...

Figure 318 The destination network 10100 is directly connected to Piglet

C COrtfteiHed. t Static, 1 l( itF', R RIP, U nohi lir, t3 ti ' i ksrp, tx ElGflP external, o OSPF, U QSPf area El OSPi 1 ir-nnl type 1, 1 . QSP nxCtir-nnJ type E EGF i is is. Li is 3 Lcvi-i. Li is is icvii 2. * ca r.rt i c a t c default IS ,163.1.8 variably subnet Tea. 2 sutniis. 2 masks S 192.160.1.0 1J0 via 192.168.1,193 c 192.168.1.192 - .' ' li directly eonrtactsd. Ethernet The next step is to trace the path of the responding ICMP echo reply packets. To trace this path, you need to know the...

Figure 322 Kangas ARP cache has an entry for Milne but the associated data link identifier is wrong

Kangaifshew a a Protocol A Jd.i.,s Internet Internet internet Internet Kanga* 172. 16,21 ,1 172.16,28,2 172.16,21,2 172.16.2fl.75 Another look at Kanga's ARP table reveals that the MAC identifier associated with Milne is suspiciously similar to the MAC identifier of Kanga's own Cisco interfaces (the MAC addresses with no ages associated with them are for the router's interfaces). Because Milne is not a Cisco product, the first three octets of its MAC identifier should be different from the...

Figure 330 The route table of RTB figure 328

Codes connected, S static, 1 liKP, h (UP, U publia, it BGP J LI RP. LH LLGRP C xt h ri a 1. OSPF, A USPF ntar ar-ea lt external type i, l2 os pi external type ' , l liif L Ii ES, M js laveJ 1, L2 IS S LovfL , ' candidate default u per user staue rauTO- Figure 3.31. The route table of RTc, figure 3.28 C Li J c- ft C connected, S -il c. I 1GHP, H KIP, u nobile, Ei H P U ElGFtP, EX EIGRP external, 0 03PF, Ii GS l in tar area > 11 (JSPI NSSA exlt-r ai type 1, FI2 OSPf HiSA asternal type 2 L1 PI...

Figure 36 Debugging verifies that the new route entries at Pooh are working correctly

IP s 192.16B.1.15 (Ethernets), J 1B.4.7.25 (Seriate , g l92,163.1.6B, forward I 10.4.7.25 (Sitr i.ilftj , C 1 Li2 . 1 ( . 1 .1 Lj (Ethernet ), (J 192.1GS.115, forward IP 192-iga. 1.1 s (Ethernet), J ti).4.7.ifM) (seriaii), y 192.163.1.34, forward IP 10.4.7.100 (Sarialo), d l92.160.1.15 (Ethernet ), g l9 .lG& .l.15, forward Next a packet is sent from host 192.168.1.15 to host 10.4.7.100. Packets destined for any host on 10.0.0.0 subnets, other than host 10.4.7.25, should be routed across the...

Figure 47 If update timers become synchronized collisions may occur

Asynchronous updates may be maintained by one of two methods Each router's update timer is independent of the routing process and is, therefore, not affected by processing loads on the router. A small random time, or timingjitter, is added to each update period as an offset. If routers implement the method of rigid, system-independent timers, then all routers sharing a broadcast network must be brought online in a random fashion. Rebooting the entire group of routers simultaneously could result...

Figure 515 The routing process in this router sees the subnets 1921681219227 and 103364020 as separate links although

Lodes- c-oiiiii r.id. 5 91 a tic ic . n 11 r. v nobiie, 2 r ii ciorp. < eicrp l iui. c C5 . a osrr area L osrr ii'.sri-ji typt 1 L2 cs eK'-err.ji type 2 ic- s . .1 Ii IE level _2 15 15 level 2 a uija'.t t TjlIL 1Z.S.J.J 255i.255.2ii. i aubnetted i 18.-M-.32.B ia directly conji-ecten ELIie-ii'.i n. i . .-15.j .12i.1i via 1s.ii.75.- a-.a-.ii. Lirtrrete n. is. i2i.-2 via tB.33.7E.1 8i iS SE. Ethernets 18.-U-.B4.B is. directly cojuiictec LLlie-1 ir.i n. 192.1EE.E3.B l2i.l via 192.tSB.12.19S., ii...

Figure 522 The routing table of RTB in Figure 520

Codes C connected, 3 static, i (Jhp, h MP, M mobile, Si iiiiP J EISRP, LX LEGHP external, 0 OSPF, IA OSPF inter area m QSPf hssa nxth rna type 1, ws o pf external type i L1 OSP cxLc nni type 1, L2 yspr axta-rnal type 2, l IG 1 i IS-IS, Li IS IS level 1, L2 IS-IS level 2, - candidate default LJ pi.11 user static route, o OOR 1 7 . in.a.ay1 ls ni-inhl subnfltted , * subnets, t masks H 172.16.24.8 22 120 1 Via 172.1B.1B.3j Ethernets rl 172.16.26.0 32 1120 2 via 173.16.18.3j (> 1< )G 2D,...

Figure 57 This router has a single entry pointing toward network 10000 The nexthop address is the boundary router since

I IS 117. F. - Rir. V rotile. 5 EST c EiCiHF, ex licrp Mtirnai, o OErr ospe inter ar-ea E1 OSif i Lii'ral typ 1. E2 BSPF Wt& Tiil fii 2. L CSP _ is is, l is level 1, L2 level 2, - GindLiiat < k(iji-. rs n .j.i. 1Z0 1 id i92 iss.nE. ao a ia, ttherneti isa.tBB.ttE.8 EE5.a55.a& s 24-B is iutfletted, i rd t t& E.iBB.d 15,32 la jiris 11 connectid . Ethurneti r 1b2.15s_115.94 iae i via 102.1 sa. i is us, bb bb ia etruj-imts c ib2.tBa.iis.ae it jires iiy...

Figure 62 LeHand advertises subnet 192168219226 to Tully as an internal route Network 19216830 is advertised to Tully

However, the local network for LeHand and Thompson is 192.168.3.0. LeHand is the boundary router between major networks 192.168.2.0 and 192.168.3.0, so 192.168.2.0 will be advertised to Thompson as a system route. Likewise, 192.168.3.0 is advertised to Tully as a system route. 192.168.1.0 is a network in another autonomous system, and LeHand has been configured to advertise that network address as a default route. 192.168.1.0 will therefore be advertised to both Thompson and Tully as an...

Figure 621 The route to 10000 via Lovett is not included in the table for load sharing

Codes c connected, b static, i lGHfj Ft hip. m one, u ugh EIGPP. L> eiGSP external, 0 OSPF , IA OiF-F inter Hrflfl 1.1 (JSP external ty,ie 1, . US F lyild EGP i 3 3, l1 is is level i, i is is level 2, - candidal default i le.e.e.e jiw ssasi via 172.is. 1.2, 00 00 11, Serlala I 192.1 SB.1.0 I 100 16601 Via 192.166.2.1, 00 00 11, Ethernets c i'jlj.directly connected, Ethernet l< )2_if Fl. .il is directly connected , Llfier-neri 132, itu.Ji.i) i0e.'S576 i i.i f9Z, 168,3,2, BB w ti, tberneti...

Figure 626 The FDDI interface of RTA in Figure 625

Hardware is uas fudi. address is aa& o.lose.did9 (bia OGaG.iefle.did9) mru 4*7 byte , aw 100000 kbit* gly 100 usee, rely 255.255, load i 255 L caiisuIn ion shah, locptjfick not sot, ketrpalive not sf.'t ARP type SNAP, AHP fifflaeut 0-1 00 00 Phy A state is off, ncignbor 1 Unknown, status, no signal Pity 3 state is off, neighbor is Unknown, status no signal ECH is out, CfU is iso la tod, rwt is isolated Requested token rotation usse, negotiated 5& 17 t tii Configured ivx is 3400 using jscc...