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that provide a way for routers to exchange routing information. The advantages of adjacencies are that they reduce the amount of link calculation and route table construction needed for a router to build a complete routing table. Routers become adjacent under different circumstances: • If a link type is point-to-point, the routers on each end will become adjacent in order for routing information to be distributed between the connected networks. • If a router is a designated router or a backup designated router on a broadcast or nonbroadcast multi-access network, adjacency is formed with all of the routers within the common network. • If a link is a virtual link, an adjacency will be formed with the backbone network, so backbone information can be exchanged. The most common instance of adjacencies is in networks where a designated router can be used. On networks where more than one router is used to provide connectivity, a designated router will be elected to represent the router group. The designated router (see Figure 8.14) will compute the routing table and exchange routing messages with other routers within the area. There is also a backup designated router, which performs the same functions if the primary fails.
Figure 8.14. OSPF router designations and adjacencies. The designated router then sends OSPF messages that announce the link states for the networks adjacent to it. The designated router in turn distributes link states for networks it learns about from other routers on the domain. The advantage of using the designated router is that route and message processing are handled by two routers instead of by every router on the network. OSPF Messages In order for OSPF to operate, a great deal of information about the status of the network must be sent, processed, and maintained. The OSPF message header and different types of messages that are used to exchange information about the OSPF domain include: • Version—Indicates the OSPF version being used. Version 2 is the current version. • Packet type—This indicates the type of message being sent. There are four message types:
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Understanding the Network A Practic
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IOS Authentication and Accounting S
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About the Reviewers These reviewers
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Tell Us What You Think As the reade
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mostly dealt with interconnecting m
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• A short introduction to SNMP Ap
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In theory, a computer network can o
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Coaxial cable has a single solid co
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• Radio transmission—It is achi
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• Baseband transmission applies t
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Ring Topology Figure 1.3. The bus t
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Packets and frames are often used a
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Asynchronous transmission involves
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Figure 1.6. Collision handling unde
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In a ring topology, a token is pass
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Repeaters The repeater was introduc
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the network. If your 50-node networ
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Figure 1.12. A collection of nodes
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their destination, type, and conten
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shop, you are using Novell's Direct
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Figure 1.14. The OSI and Internet r
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Layer 7: Application This layer pro
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end-to-end, sequenced data delivery
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outer, the delivery path might be d
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and network transport is a very imp
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Figure 1.16. The "bottom up" commun
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Chapter 2. The Networker's Guide to
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Internet Society, a nonprofit organ
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• First, it performs translations
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Figure 2.2. The IP header. • Vers
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To assist in the reassembly process
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Figure 2.3. IP address classes comp
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taking the natural mask of the addr
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Classful Subnetting Examples The im
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21 2,000 8,000 255.255.248.0 22 1,0
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classful-based address space model.
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Table 2.6. Classless Network Addres
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NOTE Because CIDR is used for addre
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will connect in the future, it is b
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Routers are also called intermediat
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IP datagrams for which the local ho
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1. The Layer 3 to Layer 2 address m
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3. Router B—Router B receives the
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connected networks. Figure 2.11 ill
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Figure 2.12. A simple regional (ISP
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gw1, gw2, gw4 3 gw1, gw3, gw4 3 gw1
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Dynamic routing might not be requir
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The transport layer as a whole repr
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window to reflect changes in the pa
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The TCP Header The TCP header provi
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53 DNS (Domain Name Service) 67 BOO
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SNMP Simple Network Management Prot
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uses both TCP and UDP for service d
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RFC 974 Mail routing and the domain
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Figure 3.1. Physical versus logical
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Figure 3.2. The AppleTalk protocol
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AppleTalk Address Resolution Protoc
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of 400 microseconds, in addition to
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Along with the SAP, there is a 5-by
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delivery is a best-effort delivery
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• DDP checksum (long header only)
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eachable within the internetwork. T
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information from the router's other
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AppleTalk Update Based Routing Prot
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• type is the service classificat
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application layers. AppleTalk has n
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Figure 3.10. ZIP message formats. E
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Printer Access Protocol Printer Acc
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Figure 3.11. Novell (IPX) protocol
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The other nodes on the network that
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Figure 3.13. IPX datagram format.
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the cumulative information gleaned
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• Hop Count is the number of rout
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Upper Layer Protocols IPX is used t
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Msg.Add.Name Adds a unique name to
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Related RFCs RFC 1001 RFC 1002 RFC
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service enhancement or replacement
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Figure 4.1. The LLC interfaces in r
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it does not provide for error recov
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and smooth pattern flow enables MTL
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cabling, backbone length 800m Categ
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combination of light refraction and
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NOTE Cladding is the glass "shell"
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Ethernet The original Ethernet prot
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UTP telephone cabling infrastructur
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Since the introduction of the IEEE
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In the event that two Ethernet end-
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The 802.3 frame type used in Figure
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• Frame check sequence (4 bytes)
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• Physical layer signaling (PLS)
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cable segment length (for coaxial s
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transmission medium using BNC (Brit
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Figure 4.12. A basic 3-cable 10Base
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Figure 4.14. 10Base-T hub-to-hub in
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Figure 4.16. 10Base-T in a consulta
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• Support for full-duplex operati
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mechanisms, in terms of encoding an
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etween different PHY encoding imple
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100Base Ethernet) is based on the p
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The Gigabit PHY The Gigabit PHY con
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CSMA/CD is sensitive to operating r
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The main advantage of using FDR ove
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have to transmit against the priori
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• Ring timing maintenance—The A
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check the lobe cable. If the lobe t
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Token Ring addresses are expressed
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• Report Active Monitor Error (RA
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they first join the ring or in the
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Figure 4.22. The IBM type 1 MIC con
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FDDI Work on the Fiber Distributed
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However, all this comes at a cost,
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Figure 4.25. FDDI MAC data frame an
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topologies needed for the transmiss
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Chapter 5. WAN Internetworking Tech
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Placing a Call The functional model
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LATAs to provide local exchange ser
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The PSTN was originally designed fo
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sampling rate is 8,000 times per se
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Figure 5.1. A multiplexer from a lo
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Table 5.1. The American (DS) and In
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The M24/D4 frame standard is the ba
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contains consecutive ones and zeros
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• Line loopback/line build-out (L
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process. The T3 multiplexer adds st
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committee. The committee provided t
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The photonic layer defines the elec
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such as T1/E1, FDDI, and others. Th
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SS7 signaling components are connec
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SCCP operates as an OSI-RM Layer 3.
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WAN point-to-point links. It can be
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Figure 5.11. The ISDN protocol refe
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• The R interface acts as a point
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• Flag—This is an 8-bit (011111
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terminals attached to the ISDN swit
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X.25 networks are comprised of four
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Frame Relay, like the ISDN effort i
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• Flag—This functions as a fram
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Figure 5.17. the B-ISDN reference m
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environments is implemented using A
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endpoints. A Virtual Path Link (VPL
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ATM endpoints. The user adaptation
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1. The ATM end-device issues a setu
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Data-Link Framing Point-to-point de
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PPP PPP can provide multiprotocol d
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PPP Framing There are three HDLC fr
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• The HDLC and PPP data-link prot
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Chapter 6. Network Switches In this
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Figure 6.1. Partial and full mesh m
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protocol. Figure 6.3 illustrates th
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All hosts can see the traffic that
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To get a better understanding of th
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Figure 6.5. A bridged LAN with span
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support a path discovery method. So
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or performance limitations, network
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network data encryption, WAN reacha
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The Impact of Switching on Traditio
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• Switch backplane—Also referre
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Switch Port Flow Control In full-du
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In the event that the primary trunk
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Figure 6.9. Layer 2 collision domai
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Figure 6.10. Multiport repeaters an
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Figure 6.11. Distributed and collap
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utilization performance. To calcula
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Ideally, the goal of all switch and
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Cut-through uses the same technolog
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VLANs A switch that supports VLAN p
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MAC Address-Based VLANs Another com
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Figure 6.13. Switches running indep
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The configuration layer uses the Ge
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Layer 2 infrastructures to operate
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need. This method not only allocate
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transmitting and receiving. Without
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ATM-specific applications would be
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ATM private-class switches are comp
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Because both the VPI and VCI are us
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environment. The goal is to have La
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Broadcast and Unknown Server The Br
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Figure 6.15. An LEC and its VCC rel
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ATM hosts are accomplished by estab
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• VLANs • Full-duplex switch po
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Chapter 7. Introduction to Cisco Ro
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The 4000 series routers come in a t
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series routers, this partition can
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need to crimp the CAT 5 strands fol
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Use the cable set to build the cabl
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Step 2. This command specifies whic
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AppleTalk FDDI IPX Token Ring VINES
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The IOS Command Line and Configurat
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disconnect Disconnect an existing n
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changes (user to privileged, for ex
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• Router(config)#hostname test-ro
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or • On 7x00 only, use: • •
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Null Null interface Tunnel Tunnel i
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Router(config)#ip rou? route routin
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Ctrl+P, up arrow Previous command i
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mop Copy from a MOP server (not ava
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Now let's see what is on the PCMCIA
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When copying any file, unless no pr
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Ethernet LANs with a dedicated T1 c
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Compiled Fri 03-Apr-98 07:00 by rna
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172.16.2.0 /25 172.16.2.128 /26 or
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Ridge-GW(config)# ip route 0.0.0.0
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In addition to their native protoco
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D - EIGRP, EX - EIGRP external, O -
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Configuring Dumb Terminal Service T
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Ctrl+Shift+6+X suspends a session).
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cornpops|Printer on Cisco termserve
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Concord-GW(config-if)#flowcontrol h
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The AUX port configuration for Ridg
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outer and enter the break sequence
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Setting the conf-reg Value in ROM M
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• Register setting 0x2010—Confi
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8. 9. Router#configure terminal 10.
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
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Router#config t Enter configuration
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-#- ED --type----crc--- -seek--nlen
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to xmodem or TFTP (2600 only) an IO
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Mountain Standard Time (MST) -7 Pac
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eference time is BB0FC7AA.95E93186
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in production for a little while. T
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use debug mode often. When using th
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uucp UNIX-to-UNIX copy system IOS a
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Log Management Logs are useless unl
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IOS Authentication and Accounting I
Page 451 and 452: hostnames (which can be corrected w
Page 453 and 454: $telnet 192.160.56.5 Trying 192.160
Page 455 and 456: In this example, the authentication
Page 457 and 458: makes it easier to configure, becau
Page 459 and 460: define what authentication type sho
Page 461 and 462: Caution should be taken when using
Page 463 and 464: pairs (similar to those used to cre
Page 465 and 466: • Using rommon and disaster recov
Page 467 and 468: In the following section, we review
Page 469 and 470: Deciding to Use a Routing Protocol
Page 471 and 472: Now, here is the qualifier: Not eve
Page 473 and 474: If RIP was the routing protocol for
Page 475 and 476: Distance Vector Protocols All routi
Page 477 and 478: space) based on a power of 2. Class
Page 479 and 480: address space), but you would run i
Page 481 and 482: destination address that falls with
Page 483 and 484: the different IP address spaces int
Page 485 and 486: Weaknesses of Static Routing Static
Page 487 and 488: Today, RIP is considered by some to
Page 489 and 490: RIP 192.124.32.0 /24 192.124.35.1 3
Page 491 and 492: All routers on the network keep tra
Page 493 and 494: RIP's Value Today RIP is old, it's
Page 495 and 496: • Better reliability—OSPF route
Page 497 and 498: Figure 8.10. Single- and multi-area
Page 499 and 500: • Internal routers—These router
Page 501: to the backbone. In Figure 8.13, al
Page 505 and 506: oundary routers. They describe netw
Page 507 and 508: outer's point of view. The path con
Page 509 and 510: Autonomous Systems and Exterior Rou
Page 511 and 512: Figure 8.16. The IGP to ERP handoff
Page 513: Figure 8.17. The BGP finite state m
Page 516 and 517: EGPs have been increasing in popula
Page 518 and 519: Chapter 9. Advanced Cisco Router Co
Page 520 and 521: specified ACL number range. Table 9
Page 522 and 523: default, all traffic is denied. Onl
Page 524 and 525: asbr-a2#config t Enter configuratio
Page 526 and 527: trying to build ACLs with the comma
Page 528 and 529: trace Multicast trace IGMP log Log
Page 530 and 531: Tftp Trivial File Transfer Protocol
Page 532 and 533: access-list 100 permit tcp any 172.
Page 534 and 535: Table 9.5. AppleTalk ACL Filtering
Page 536 and 537: Figure 9.1. The AnyCo corporate App
Page 538 and 539: One word of caution: If you plan to
Page 540 and 541: You can also log hits on ports by a
Page 542 and 543: Table 9.8. Route-Map Operators for
Page 544 and 545: exists, a group identifier (which c
Page 546 and 547: hegel# With this configuration, bec
Page 548 and 549: NAT is commonly used in a fashion s
Page 550 and 551: The [prefix-length] or [netmask] se
Page 552 and 553:
NAT's Shortcomings Although NAT is
Page 554 and 555:
NOTE Administrators beware: Tunneli
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connects, the active key informatio
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encapsulation, framing, and line si
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asbr-a2(config-if)#ip address 172.1
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problem if you are provisioning ISD
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22:41:34: %LINK-3-UPDOWN: Interface
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POP mail request is made. Now let's
Page 568 and 569:
leibniz(config-if)#backup interface
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When the primary link fails, the BR
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1.544Mbps. The actual transport lin
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the cost-effective and bandwidth-ef
Page 576 and 577:
interface configuration subcommand
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it is possible to exchange packets
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interface serial0.2 point-to-point
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Figure 9.6. A multipoint FR example
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2. ATM encapsulation must be enable
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are commonly used in large-scale cl
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persephone(config)#interface atm 3/
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• The creation and application of
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Chapter 10. Configuring IP Routing
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After you have a list of requiremen
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Control commands: Displaying
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not active, it is quite common for
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Incoming update filter list for all
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When changing any IP routing behavi
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asbr-a1(config-if)#^Z asbr-a1# When
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For asbr-a2 to reach all the testne
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192.168.160.0/30 is subnetted, 1 su
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order to maintain computability wit
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Configuring Dynamic IGP and EGP IP
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passive-interface s1 By enabling th
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asbr-a1(config-router)#network 12.0
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To verify that the adjusted route m
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The command is a general routing p
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EIGRP, as I'm sure you have guessed
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No matter how the announcement entr
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Incoming update filter list for all
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is adjustable using the router con
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• IOS also supports various debu
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outers: • Backbone Routers—Thes
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process. The router would construct
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e1/1 192.168.9.0 fe0/0 192.168.0.0
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An alternative to this is to use th
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C 192.168.191.0/24 is directly conn
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Link State Age Interval is 00:20:00
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C 192.168.191.0/24 is directly conn
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to asbr-a1 was a remote office that
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interface Serial1 ip address 192.16
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which to exchange OSPF messages. Th
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OSPF Monitoring Commands Throughout
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• • • NOTE • will display
Page 656 and 657:
Figure 10.4. AURP tunnel interfaces
Page 658 and 659:
appletalk glean-packets hostname as
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For many users, the usefulness of B
Page 662 and 663:
internal/Internet access router whe
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externally destined traffic arrives
Page 666 and 667:
Routers asbr-a1/a2 and asbr-b1/b2 a
Page 668 and 669:
BGP Reflectors An alternative to ha
Page 670 and 671:
network 192.168.0.0 mask 255.255.25
Page 672 and 673:
dynamic routing protocols are used
Page 674 and 675:
Figure 10.8. An example network run
Page 676 and 677:
Controlling Redistribution In some
Page 678 and 679:
hostname ABR-a57 ! access-list 1 pe
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access-list 2 deny 10.0.1.0 access-
Page 682 and 683:
Keep in mind that route-maps, li
Page 684 and 685:
Chapter 11. Network Troubleshooting
Page 686 and 687:
However, the most valuable tool of
Page 688 and 689:
• Description of primary function
Page 690 and 691:
of cable fault, different CSFSs are
Page 692 and 693:
For Windows Systems, check out the
Page 694 and 695:
command. On a Windows NT system, us
Page 696 and 697:
#Do not change these variables logf
Page 698 and 699:
# If any of the hosts fail to respo
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upgrade. So, when the time comes to
Page 702 and 703:
throughput over time, instead of si
Page 704 and 705:
protocol is the most prone to perfo
Page 706 and 707:
NOTE When looking at network broadc
Page 708 and 709:
NOTE Another common network error n
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and the physical ring segment that
Page 712 and 713:
tolerances the frames, timing shift
Page 714 and 715:
practical terms, this means that at
Page 716 and 717:
etransmissions, however, usually ha
Page 718 and 719:
4. Don't get lost in the big pictur
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• Link and services monitoring, n
Page 722 and 723:
eports on network utilization, avai
Page 724 and 725:
o Bandwidth utilization rates o Rat
Page 726 and 727:
and improved management capabilitie
Page 728 and 729:
After the supported SNMP version is
Page 730 and 731:
Table 11.3. ASN.1 Keywords Used wit
Page 732 and 733:
application-wide tags, which are us
Page 734 and 735:
TestSequence ::= SEQUENCE { example
Page 736 and 737:
The MIB-2 and RMON-MIB modules are
Page 738 and 739:
iso.identfied-orgnaization.dod.inte
Page 740 and 741:
accepted values are getRequest, get
Page 742 and 743:
Spectrum is available in both UNIX
Page 744 and 745:
Figure 11.8. Windows NT 4.0 SNMP Ag
Page 746 and 747:
To access any of the NT SNMP agent
Page 748 and 749:
The installation of the SNMP agent
Page 750 and 751:
Figure 11.13. The Windows 95/98 Sel
Page 752 and 753:
Figure 11.15. Locating the Windows
Page 754 and 755:
Figure 11.17. The SNMP configuratio
Page 756 and 757:
2. Scroll to Network Connectivity o
Page 758 and 759:
sysLocation information, go to the
Page 760 and 761:
example that just implements the ba
Page 762 and 763:
protocol, service, and application
Page 764 and 765:
RFC 1089 RFC 1147 RFC 1155 RFC 1157
Page 766:
Appendix A. Binary Conversion Table
show all

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