CCIE cert!! - A Catalyst Way to Cisco Certification

here ’s a note file i wrote, all of the text was copy & paste from Cisco Documentation CD and Training books.
Presentation layer implementations are not typically associated with a particular protocol stack. Some well known standards follow: Data: ASCII, EBCDIC, Encryption Visual Imaging: PICT, TIFF, GIF, JPEG Video: MIDI, MPEG, QuickTime Session — This layer establishes, manages, and terminates communication sessions between presentation layer entities. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session layer implementations follow: Apple ZIP, DEC SCP, NFS, SQL, RPC, X Windows, ASP. Transport — This layer segments and reassembles data into a data stream. It implements reliable internetwork data transport services that are transparent to upper layers. Transport layer functions typically include the following: Flow control — Flow control manages data transmission between devices so that the transmitting device does not send more data than the receiving device can process. Multiplexing — Multiplexing allows data from several applications to be transmitted onto a single physical link. Virtual circuit management — Virtual circuits are established, maintained, and terminated by the transport layer. Error checking and recovery — Error checking involves various mechanisms for detecting transmission errors. Error recovery involves taking an action (such as requesting that data be retransmitted) to resolve any errors that occur. Some examples of transport layer implementations follow: Transmission Control Protocol (TCP), Name Binding Protocol (NBP), OSI transport protocols. Network — This layer provides routing and related functions that allow multiple data links to be combined into an internetwork, and determines the best way to move to data from one place to another. (It manages device addressing and tracks the location of devices on the network.) This is accomplished by the logical addressing (as opposed to the physical addressing) of devices. The network layer supports both connection-oriented and connectionless service from higher-layer protocols. The router operates at this layer. Data Link — provides reliable transit of data across a physical network link. Different data link layer specifications define different network and protocol characteristics, including the following: Physical addressing — Physical addressing (as opposed to network addressing) defines how devices are addressed at the data link layer. Network topology — Data link layer specifications often define how devices are to be physically connected (such as in a bus or a ring topology). Error notification — Error notification involves alerting upper layer protocols that a transmission error has occurred. Sequencing of frames — Sequencing of data frames involves the reordering of frames that are transmitted out of sequence. Flow control — Flow control involves moderating the transmission of data so that the receiving device is not overwhelmed with more traffic than it can handle at one time. The Institute of Electrical and Electronics Engineers (IEEE) has subdivided the data link layer into two sublayers: Logical Link Control (LLC) and Media Access Control (MAC). The LLC sublayer (defined in the IEEE 802.2 specification) manages communications between devices over a single link of a network. The MAC sublayer manages protocol access to the physical network medium. Physical — This layer defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link between communicating network systems. Physical layer specifications define such characteristics as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, and the physical connectors to be used. 2) Describe connection-oriented network service and connectionless network service, and identify the key differences between them. In brief, connection-oriented data handling involves using a specific path that is established for the duration of a connection. Connectionless data handling involves passing data through a permanently established connection. Connection-oriented service involves three phases: Connection establishment — During the connection establishment phase, a single path between the source and destination systems is determined. Network resources are typically reserved at this time to ensure a consistent grade of service (such as a guaranteed throughput rate). Data transfer — During the data transfer phase, data is transmitted sequentially over the path that has been established. Data always arrives at the destination system in the order in which it was sent. Connection termination — During the connection termination phase, an established connection that is no longer needed is terminated. Further communication between the source and destination systems requires that a new connection be established. Connection-oriented service has two significant disadvantages as compared to connectionless network service: Static path selection — Because all traffic must travel along the same static path, a failure anywhere along that path causes the connection to fail. Static reservation of network resources — A guaranteed rate of throughput requires the commitment of resources that cannot be shared by other network users. Unless full, uninterrupted throughput is required for the communication, bandwidth is not used efficiently. Connection-oriented services are useful for transmitting data from applications that are intolerant of delays and packet re-sequencing. Voice and video applications are typically based on connection-oriented services. Connectionless network service does not predetermine the path from the source to the destination system, nor are packet sequencing, data throughput, and other network resources guaranteed. Each packet must be completely addressed because different paths through the network might be selected for different packets, based on a variety of influences. Each packet is transmitted independently by the source system and is handled independently by intermediate network devices. Connectionless service, however, offers two important advantages over connection-oriented service: dynamic-path selection and dynamic-bandwidth allocation. Dynamic-path selection enables traffic to be routed around network failures because paths are selected on a packet-by-packet basis. Dynamic-bandwidth allocation, bandwidth is used more efficiently because network resources are not allocated a bandwidth that they will not use. Connectionless services are useful for transmitting data from applications that can tolerate some delay and resequencing. Data-based applications typically are based on connectionless service.
3) Describe data link addresses and network addresses, and identify the key differences between them. A data link layer address uniquely identifies each physical network connection of a network device. Data link addresses are sometimes referred to as physical or hardware addresses. Data link addresses usually exist within a flat address space and have a pre-established and typically fixed relationship to a specific device. End systems typically have only one physical network connection, and thus have only one data link address. Routers and other internetworking devices typically have multiple physical network connections. They therefore have multiple data link addresses. A network-layer address identifies an entity at the network layer of the OSI layers. Network addresses usually exist within a hierarchical address space and sometimes are called virtual or logical addresses. The relationship between a network address and a device is logical and unfixed; it typically is based either on physical network characteristics (the device is on a particular network segment) or on groupings that have no physical basis (the device is part of an AppleTalk zone). End systems require one network-layer address for each network-layer protocol they support. (This assumes that the device has only one physical network connection.) Routers and other internetworking devices require one network-layer address per physical network connection for each network-layer protocol supported. A router, for example, with three interfaces each running AppleTalk, TCP/IP, and OSI must have three network-layer addresses for each interface. The router therefore has nine network-layer addresses.
4) Identify at least 3 reasons why the industry uses a layered model. Reduces complexity — Divide the interrelated aspects of network operation into less complex elements. Standardizes interfaces — Define standard interfaces for “plug-and-play” compatibility and multivendor integration. Facilitates module reengineering — Enable engineers to specialize design and development efforts on modular functions. Ensures interoperable technology — Promote symmetry in the different internetwork modular functions so they interoperate. Accelerates evolution — Prevent changes in one area from impacting other areas, so each are can evolve more quickly. Simplifies teaching and learning — Divide the complexity of internetworking into discrete, more easily learned operation subsets.
5) Define and explain the 5 conversion steps of data encapsulation. User information is converted to data Data — As an user sends an email message, the messages alphanumeric characters are converted to use the internetwork. This is the data. Data is converted to Segments Segment — One change packages the message “data” for the internetwork transport subsystem. By using segments, the transport function ensures that the message hosts at both ends of the email system can reliably communicate. Segments are converted to Packets Packet — The next change prepares the data by putting the data into a packet or datagram that contains a network header with source and destination logical addresses. These addresses help network devices send the packets across the network alone a chosen path. Packets are converted to Frames Frame — Each network devices must put the packet into a frame so it can communicate over its interface to the network. The frame allows connection to the net directly connected network device on the link. Each device in the chosen network path requires framing to connect to the next device. Frames are converted to Bits Bits — The frame must be converted into a pattern of 1s and 0s for transmission on the medium ( usually a wire ). Some clocking function enables the devices to distinguish these bits as they traverse the medium.
6) Define flow control and describe the three basic methods used in networking. Flow control — It’s a function that prevents network congestion by ensuring that transmitting devices do not overwhelm receiving devices with data. The three commonly used methods for handling network congestion are buffering, transmitting source-quench messages, and windowing. Buffering - Buffering is used by network devices to temporarily store bursts of excess data in memory until they can be processed. Occasional data bursts are easily handled by buffering. However, excess data bursts can exhaust memory, forcing the device to discard any additional datagrams that arrive. Source quench messages - Source quench messages are used by receiving devices to help prevent their buffers from overflowing. The receiving device sends source quench messages to request that the source reduce its current rate of data transmission, as follows: 1. The receiving device begins discarding received data due to overflowing buffers. 2. The receiving device begins sending source quench messages to the transmitting device, at the rate of one message for each packet dropped. 3. The source device receives the source quench messages and lowers the data rate until it stops receiving the messages. 4. The source device then gradually increases the data rate as long as no further source quench requests are received. Windowing - Windowing is a flow-control scheme in which the source device requires an acknowledgement from the destination after a certain number of packets have been transmitted. With a window size of three, the source requires an acknowledgment after sending three packets, as follows: 1. The source device sends three packets to the destination device. 2. After receiving the three packets, the destination device sends an acknowledgment to the source. 3. The source receives the acknowledgment and sends three more packets. 4. If the destination does not receive one or more of the packets for some reason (such as overflowing buffers), it does not receive enough packets to send an acknowledgment. The source, not receiving an acknowledgment, retransmits the packets at a reduced transmission rate.
7) List the key internetworking functions of the OSI Network layer and how they are performed in a router. The network layer provides routing and related functions that enable multiple data links to be combined into an internetwork. It selects the best path through an internetwork, establishes network addresses, and communicates paths. This is accomplished by the logical addressing (as opposed to the physical addressing) of devices. The network layer supports both connection-oriented and connectionless service from higher-layer protocols. Network-layer protocols typically are routing protocols, but other types of protocols are implemented at the network layer as well. Routers use a routing protocol between routers, use a routed protocol to carry user packets, set up and maintain routing tables, discover networks, adapt to internetwork topology changes, use a two part address, and contains broadcasts.
WAN Protocols Differentiate between the following WAN services: Frame Relay, ISDN/LAPD, HDLC, & PPP. Frame Relay - Industry-standard, switched data link layer protocol that handles multiple virtual circuits using HDLC encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it is generally considered a replacement. ISDN - Integrated Services Digital Network. Communication protocol, offered by telephone companies, that permits telephone networks to carry data, voice, and other source traffic. HDLC - High-Level Data Link Control. Bit-oriented synchronous data link layer protocol developed by ISO. Derived from SDLC, HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums. PPP - Point-to-Point Protocol. A successor to SLIP, PPP provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. A point-to-point link provides a single, preestablished WAN communications path from the customer premises through a carrier network, such as a telephone company, to a remote network. ( HDLC, & PPP ) Circuit switching is a WAN switching method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session. ( ISDN/LAPD ) Packet switching is a WAN switching method in which network devices share a single point-to-point link to transport packets from a source to a destination across a carrier network. ( Frame Relay )
9) Recognize key Frame Relay terms and features. Frame Relay is a CCITT & ANSI standard for sending data over a public data network. It is a next-generation protocol to X.25 and is a connection-oriented data-link technology. It relies on upper-layer protocols for error correction and today’s more dependable fiber and digital networks. Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model. Frame Relay is an example of a packet-switched technology. Packet-switched networks enable end stations to dynamically share the network medium and the available bandwidth. Variable-length packets are used for more efficient and flexible transfers. The advantage of this technique is that it accommodates more flexibility and more efficient use of bandwidth. Frame Relay provides connection-oriented data link layer communication. (This means that a defined communication exists between each pair of devices and that these connections are associated with a connection identifier.) This service is implemented by using a Frame Relay virtual circuit, which is a logical connection created between two data terminal equipment (DTE) devices across a Frame Relay packet-switched network (PSN). Virtual circuits provide a bi-directional communications path from one DTE device to another and are uniquely identified by a data-link connection identifier (DLCI). A number of virtual circuits can be multiplexed into a single physical circuit for transmission across the network. This capability often can reduce the equipment and network complexity required to connect multiple DTE devices. Frame Relay virtual circuits fall into two categories: switched virtual circuits (SVCs) and permanent virtual circuits (PVCs). Some terms frequently when discussing Frame Relay follow: Local access rate — The clock speed (port speed) of the connection (local loop) to the Frame Relay cloud. It is the rate at which data travels into or out of the network, regardless of other settings. Data-link connection identifier (DLCI) — A number that identifies the logical circuit between the CPE/DTE and the Frame Relay switch. The FR switch maps the DLCIs between each pair of routers to create a PVC. DLCIs have local significance in that the identifier references the point between the local router and the Frame Relay switch to which it is connected. Local Management Interface (LMI) — A signaling standard between the CPE device and the FR switch that is responsible for managing the connection and maintaining status between the devices. LMIs include support for a keepalive mechanism, which verifies that data is flowing; a multicast mechanism, which provides the network server with it’s local DLCI; the multicast addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a status mechanism, which provides an ongoing status on the DLCIs known to the switch. The following types of LMIs are supported by Cisco routers (IOS 11.2 or later): cisco — LMI type define jointly bye Cisco, Northern Telecom, and DEC; ansi — Annex D defined by ANSI standard T1.617; q933a — ITU-T Q.933 Annex A Committed information rate (CIR) - the average rate (bps) that the FR switch agrees to transfer data. Committed burst - the maximum number of bits that the switch agrees to transfer during any Committed Rate Measurement Interval. Excess burst - the maximum number of uncommitted bits that the FR switch will attempt to transfer beyond the CIR (typically limited to the port speed of the local access loop). Backward explicit congestion notification (BECN) - when a FR switch recognizes congestion in the network, It sends a BECN packet to the source router instructing it to reduce its packet sending rate. Forward explicit congestion notification (FECN) - when a FR switch recognizes congestion in the network, It sends a FECN packet to the destination device indicating that congestion has occurred. Discard eligibility (DE) indicator - when the router detects network congestion, the FR switch will drop packets with the DE bit set first. The DE bit is set on the oversubscribed traffic; that is the traffic that was received after the CIR was met.
10) List commands to configure Frame Relay LMIs, maps, and subinterfaces. router(config-if)# encapsulation frame-relay [ cisco | ietf ] (cisco is the default) router(config-if)# frame-relay lmi-type [ ansi | cisco | q933i ] (autosensed 11.2 and up) router(config-if)# bandwidth kilobits (configur bandwidth for the link, default is T1) router(config-if)# frame-relay inverse-arp [ protocol ] [ dlci ] (enabled by default) router(config-if)# ip bandwidth-percent eigrp as-number percent (total bandwidth EIGRP can use) router(config-if)# keepalive number ( increase/decrease keepalive interval, default is 10 secs.) router(config-if)# frame-relay local-dlci number (to specify DLCI for local interface) router(config-if)# frame-relay map protocol protocol-address dlci [broadcast ] [ ietf | cisco ] payload-compress packet-by-packet (Cisco compression) (broadcast - forward broadcasts to this address when multicast is not enabled) router(config-if)# interface serial number . subinterface-number [multipoint | point-to-point ] (multipoint - forwards broadcasts and routing updates, for routing IP when all routers are in same subnet) (point-to-point - no broadcasts or updates, each router is in its own subnet) router(config-if)# ip unnumbered interface (point-to-point IP sub-interface) router(config-if)# frame-relay interface-dlci dlci-number (local DLCI number being linked to sub-interface) The following is a partial config example: interface Serial 0 encapsulation frame-relay frame-relay lmi-type ansi ! interface Serial 0.1 point-to-point ip address 192.168.155.1 255.255.255.252 frame-relay interface-dlci 123 interface Serial 0 encapsulation frame-relay frame-relay lmi-type ansi ! interface Serial 0.1 point-to-point ip address 192.168.155.2 255.255.255.252 frame-relay interface-dlci 124
11) List commands to monitor Frame Relay operation in the router. To monitor Frame Relay connections, perform any of the following tasks in EXEC mode: Task Command Clear dynamically created Frame Relay maps, which are created by the use of Inverse ARP. clear frame-relay-inarp Display information about Frame Relay DLCIs and the LMI. show interfaces type number Display LMI statistics. show frame-relay lmi [type number] Display the current Frame Relay map entries. show frame-relay map Display PVC statistics. show frame-relay pvc [type number [dlci]] Display configured static routes. show frame-relay route Display Frame Relay traffic statistics. show frame-relay traffic Display information about the status of LAPF. show frame-relay lapf Display all the SVCs under a specified map list. show frame-relay svc maplist 12) Identify PPP operations to encapsulate WAN data on Cisco routers. The Point-to-Point Protocol (PPP) originally emerged as an encapsulation protocol for transporting IP traffic over point-to-point links. PPP also established a standard for the assignment and management of IP addresses, asynchronous (start/stop) and bit-oriented synchronous encapsulation, network protocol multiplexing, link configuration, link quality testing, error detection, and option negotiation for such capabilities as network-layer address negotiation and data-compression negotiation. PPP supports these functions by providing an extensible Link Control Protocol (LCP) and a family of Network Control Protocols (NCPs) to negotiate optional configuration parameters and facilities. In addition to IP, PPP supports other protocols, including Novell’s Internetwork Packet Exchange (IPX) and DECnet. PPP provides a method for transmitting datagrams over serial point-to-point links. PPP contains three main components: A method for encapsulating datagrams over serial links — PPP uses the High-Level Data Link Control (HDLC) protocol as a basis for encapsulating datagrams over point-to-point links. (See “Synchronous Data Link Control and Derivatives,” for more information on HDLC.) An extensible LCP to establish, configure, and test the data-link connection. A family of NCPs for establishing and configuring different network-layer protocols—PPP is designed to allow the simultaneous use of multiple network-layer protocols. The following is a common procedure to configure PPP in your Cisco routers: Router(config)# username name password secret (name=host name of remote router, Secret=identical on both routers) Router(config-if)# encapsulation ppp Router(config-if)# ppp authentication [chap | pap ] (pap is clear text) Router(config-if)# ppp pap sent-username username password password (for router responding to pap request, 11.1 and up) Router(config-if)# ppp chap hostname hostname (for same host name onmultiple routers) Router(config-if)# ppp chap password secret (to send to hosts that want to authenticate the router)
13) State a relevant use and context for ISDN networking. The goal is o support applications requiring high speed voice, video, and data communications.Digital service with fast connection setup and higher bandwidth than traditional modems. Integrated Services Digital Network (ISDN) is comprised of digital telephony and data-transport services offered by regional telephone carriers. ISDN involves the digitalization of the telephone network, which permits voice, data, text, graphics, music, video, and other source material to be transmitted over existing telephone. The emergence of ISDN represents an effort to standardize subscriber services, user/network interfaces, and network and internetwork capabilities. ISDN applications include high-speed image applications (such as Group IV facsimile), additional telephone lines in homes to serve the telecommuting industry, high-speed file transfer, and video conferencing. Voice service is also an application for ISDN. ISDN components include terminals, terminal adapters (TAs), network-termination devices, line-termination equipment, and exchange-termination equipment.
14) Identify ISDN protocols, function groups, reference points, and channels. ITU-T groups and organizes the ISDN protocols according to general topic areas. Protocols that begin with “E” recommend telephone network standards for ISDN. For example, The E.164 protocol describes international adressing for ISDN. Protocols that begin with “I” Deal with concepts, terminology, and general methods. The I.100 series includes general ISDN concepts and the structure of other I-series recommendations; I.200 deals with service aspects of ISDN; I.300 describes network aspects; I.400 describes how the User-Network Interface (UNI) is provided. Protocols beginning with “Q” cover how switching and signaling should operate. The term signaling in this context means the process of call set used. Q.921 describes the ISDN data-link processes of LAPD, which functions like Layer 2 processes in the ISO/OSI reference model. Q.931 specifies ISO/OSI reference model Layer 3 functions. To access ISDN, you must provide functions and reference points that comply with ISDN service provider standards. By using these functions and reference points, you can improve communication with vendors and service providers while you engineer, install, and support your ISDN facilities: Functions — Device types or hardware functions that represent transition points between the reference-point interfaces. Reference points — CCITT has defined the ISDN local loop characterized by different interfaces. The standards call the key reference points R, S, T, U, and V. R–The reference point between non-ISDN equipment and a TA. S–The reference point between user terminals and the NT2. T–The reference point between NT1 and NT2 devices. U–The reference point between NT1 devices and line-termination equipment in the carrier network. The U reference point is relevant only in North America, where the NT1 function is not provided by the carrier network.  This Figure illustrates a sample ISDN configuration and shows three devices attached to an ISDN switch at the central office. Two of these devices are ISDN-compatible, so they can be attached through an S reference point to NT2 devices. The third device (a standard, non-ISDN telephone) attaches through the reference point to a TA. Any of these devices also could attach to an NT1/2 device, which would replace both the NT1 and the NT2. In addition, although they are not shown, similar user stations are attached to the far right ISDN switch. The following table defines the basic ISDN device or hardware acronym and it’s function. AcronymDevice NameDevice FunctionTATerminal AdapterConterts from EIA/TIA-232, V.35, and other signals into BRI signals.TE1Terminal Endpoint 1Designates a rotuer as a device having a native ISDN interface.TE2Terminal Endpoint 2Designates a router as a device requiring a TA for it’s BRI signals.NT1Network Termination 1Converts BRI signals into a form used by the ISDN digital line.LTLocal TerminationPortion of the local exchange that terminates the local loop.ETExchange TerminationPortion of the exchange that communicates with other ISDN componets. The ISDN Basic Rate Interface (BRI) service offers two B channels and one D channel (2B+D). BRI B-channel service operates at 64 kbps and is meant to carry user data; BRI D-channel service operates at 16 kbps and is meant to carry control and signaling information, although it can support user data transmission under certain circumstances. The D channel signaling protocol comprises Layers 1 through 3 of the OSI reference model. BRI also provides for framing control and other overhead, bringing its total bit rate to 192 kbps. ISDN Primary Rate Interface (PRI) service offers 23 B channels and one D channel in North America and Japan, yielding a total bit rate of 1.544 Mbps (the PRI D channel runs at 64 Kbps). ISDN PRI in Europe, Australia, and other parts of the world provides 30 B channels plus one 64-Kbps D channel and a total interface rate of 2.048 Mbps.
ISDN physical-layer (Layer 1) frame formats differ depending on whether the frame is outbound (from terminal to network) or inbound (from network to terminal). The frames are 48 bits long, of which 36 bits represent data. Layer 2 of the ISDN signaling protocol is Link Access Procedure, D channel, also known as LAPD. LAPD is similar to High-Level Data Link Control (HDLC) and Link Access Procedure, Balanced (LAPB). As the expansion of the LAPD acronym indicates, it is used across the D channel to ensure that control and signaling information flows and is received properly. The LAPD frame format is very similar to that of HDLC and, like HDLC, LAPD uses supervisory, information, and unnumbered frames. The LAPD protocol is formally specified in ITU-T Q.920 and ITU-TQ.921. Two Layer 3 specifications are used for ISDN signaling: ITU-T (formerly CCITT) I.450 (also known as ITU-T Q.930) and ITU-T I.451 (also known as ITU-T Q.931). Together, these protocols support user-to-user, circuit-switched, and packet-switched connections. A variety of call establishment, call termination, information, and miscellaneous messages are specified, including SETUP, CONNECT, RELEASE, USER INFORMATION, CANCEL, STATUS, and DISCONNECT. These messages are functionally similar to those provided by the X.25 protocol.
15) Describe Cisco’s implementation of ISDN BRI. Two 64 Kbps B channels and one 16 Kbps D channel. Accessing ISDN with a Cisco router means that you will need to purchase either a Network Termination 1 (NT1) or an ISDN modem. If your router has a BRI interface, you’re readyto rock. Otherwise, you can use one of your router’s serial interfaces if you can get a hold of a TA. A router with a BRI interface is call a TE1, and one that requires a TA is called a TE2. ISDN supports virtually every upper-layer network protocol (IP, IPX, and AppleTalk), and you can choose PPP, HDLC, or LAPD as your encapsulation protocol.

IOS 16) Log into a router in both user and privileged modes. You can configure Cisco routers from the user interface that runs on the router console or terminal. You can also configure Cisco routers using remtoe access. Cisco IOS software provides a command interpreter called EXEC. EXEC interprets the commands you type and carries out the corresponding operations. You must log in to the router before you can enter an EXEC command. For security purposes, the EXEC has two levels of access to commands: user mode and privileged mode. User Mode — Typical tasks include those that check the router status. ( The prompt is: Router> ) Privileged mode — Typical tasks include those that change the router configuration. ( The prompt is: Router# ) The following is a demo procedure: Router> Router> enable Password: Router# Router# disable Router> Router> exit
17) Use the context-sensitive help facility. Typing a quesion mark (?) at the user mode prompt or the privileged mode prompt displays a handy list of commonly used commands. With the context-sensitive help, you can do the following: Symbolic translation Keyword completion Last command recall

Command prompting Syntax checking and the caret symbol (^) and help response indicate and error. It appears at the point in the command string where you have entered and incorrect command, keyword, orargument. The error location indicator and interactive help system allow you to find and correct syntax error easily.
18) Use the command history and editing features. The user interface includes and enhanced editing mode that provides a set of editing key functions. ; Automatic scrolling of long lines. ; Move to the beginning of the command line. ; Move to the end of the command line. ; Move back one word. ; Move foward one character. ; Move back one character. ; Move forward one word.

or UP arrow ; Last (previous) command recall or DOWN arrow ; More recent command recall Router> show history ; Show command buffer Router> terminal history size number-of-lines ; Set command buffer size Router> no terminal editing ; Disable advanced editing features Router> terminal editing ; Reenable advanced editing ; Entry completion
19) Examine router elements (RAM, ROM, CDP, show). ROM - Read Only, Hard Wired, Boot Strap, IOS, ROM Monitor RAM - IOS & Running Configuration (Main Memory) NVRAM - Startup Config ? Saved via battery (10 yr Life Span) Flash - IOS (PCMCIA Cards or SIMMs) Shared RAM - Packet Buffering (Not all platforms) The Cisco Discovery Protocol (CDP) is a media- and protocol-independen protocol that runs on all Cisco-manufactured equipment including routers, bridges, access servers and switches. CDP runs on all media that supports Subnetwork Access Protocol (SNAP) including local area network, Frame Relay and ATM media. CDP runs over the data link layer only. Specify the frequency of transmission of CDP updates. show version — Displays the configuration of the system hardware, the software version, the names and sources of configuration files, and boot images. show mem — Shows statistics about the router’s memory, including memory free pool statistics. show cdp [interface | neighbors | entry device-name] — Shows CDP statistics. show protocols — Displays the protocols configured on the router.
20) Manage configuration files from the privileged exec mode. show startup-config — To view the configuration in NVRAM (show config = pre10.3) show running-config — To view the current running configuration (write term = pre 10.3) show version