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EGPs have been increasing in popularity among network administrators because of their flexibility. You as a network administrator need to be aware of the role they have in routing traffic across the Internet. Configuring BGP will be addressed in Chapter 10, "Using IP Routing Protocols on Cisco Routers." Policy routing will be addressed in Chapter 9, "Advanced Routing Options and Configuration." Summary At this point, you should have a good understanding of routing concepts, including the strengths and weaknesses of the protocols, how they're used and why. We focused on the open protocol standards EIGRP and IGRP, OSPF, IGP and ERP, RIP and BGP. You should be familiar with the factors that affect dynamic routing, such as metrics and convergence, and how each protocol adjusts to changes in the network's configuration and state. Related RFCs RFC 827 Exterior Gateway Protocol (EGP) RFC 1058 Routing Information Protocol RFC 1131 OSPF Specification RFC 1265 BGP Protocol Analysis RFC 1266 Experience with the BGP Protocol RFC 2082 RIP-2 MD5 Authentication RFC 2178 OSPF Version 2 RFC 1700 Assigned TCP/IP Port Numbers RFC 1721 RIP Version 2 Protocol Analysis RFC 1771 A Border Gateway Protocol 4 (BGP-4) Additional Resources Halabi Bassam. Internet Routing Architectures. Cisco Press, 1997. Moy John T. OSPF: Anatomy of an Internet Routing Protocol. Addison-Wesley, 1998. Stewart John W. BGP4, Inter-Domain Routing in the Internet. Addison-Wesley, 1998.
Tanenbaum Andrew S. Computer Networks. Third Edition. Prentice Hall, 1996.
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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
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hostnames (which can be corrected w
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$telnet 192.160.56.5 Trying 192.160
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In this example, the authentication
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makes it easier to configure, becau
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define what authentication type sho
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Caution should be taken when using
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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 and 502: to the backbone. In Figure 8.13, al
Page 503 and 504: Figure 8.14. OSPF router designatio
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 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
Page 556 and 557: connects, the active key informatio
Page 558 and 559: encapsulation, framing, and line si
Page 560 and 561: asbr-a2(config-if)#ip address 172.1
Page 562 and 563: problem if you are provisioning ISD
Page 564 and 565: 22:41:34: %LINK-3-UPDOWN: Interface
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POP mail request is made. Now let's
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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
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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
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Figure 10.4. AURP tunnel interfaces
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appletalk glean-packets hostname as
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For many users, the usefulness of B
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internal/Internet access router whe
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externally destined traffic arrives
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Routers asbr-a1/a2 and asbr-b1/b2 a
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BGP Reflectors An alternative to ha
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network 192.168.0.0 mask 255.255.25
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dynamic routing protocols are used
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Figure 10.8. An example network run
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Controlling Redistribution In some
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hostname ABR-a57 ! access-list 1 pe
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access-list 2 deny 10.0.1.0 access-
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Keep in mind that route-maps, li
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Chapter 11. Network Troubleshooting
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However, the most valuable tool of
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• Description of primary function
Page 690 and 691:
of cable fault, different CSFSs are
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For Windows Systems, check out the
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command. On a Windows NT system, us
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#Do not change these variables logf
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# If any of the hosts fail to respo
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upgrade. So, when the time comes to
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throughput over time, instead of si
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protocol is the most prone to perfo
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NOTE When looking at network broadc
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NOTE Another common network error n
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and the physical ring segment that
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tolerances the frames, timing shift
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practical terms, this means that at
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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
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eports on network utilization, avai
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o Bandwidth utilization rates o Rat
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and improved management capabilitie
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After the supported SNMP version is
Page 730 and 731:
Table 11.3. ASN.1 Keywords Used wit
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application-wide tags, which are us
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TestSequence ::= SEQUENCE { example
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The MIB-2 and RMON-MIB modules are
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iso.identfied-orgnaization.dod.inte
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accepted values are getRequest, get
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Spectrum is available in both UNIX
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Figure 11.8. Windows NT 4.0 SNMP Ag
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To access any of the NT SNMP agent
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The installation of the SNMP agent
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Figure 11.13. The Windows 95/98 Sel
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Figure 11.15. Locating the Windows
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Figure 11.17. The SNMP configuratio
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2. Scroll to Network Connectivity o
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sysLocation information, go to the
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example that just implements the ba
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protocol, service, and application
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RFC 1089 RFC 1147 RFC 1155 RFC 1157
Page 766:
Appendix A. Binary Conversion Table
show all

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