RameshsStudyGuide （上）
添加时间: 2007-9-3 21:55:21 作者: Cisco认证考试 阅读次数:45 来源: http://www.d9soft.com
Here is my latest Dump of CCNA exam which i took today with a score of 810.
It was quite difficult unlike my expectation. The questions were from from the normal topics except few. However most of these questions were very badly worded Both gramatically and technically to confuse the guys. I think it is deliberately done by Cisco to fail the poor guys and make more money.
So Here is Comprehensive Exam Cram for many of you preparing for CCNA. This cram was prepared by myself, quite a lot of hardwork behind this, i am sure you will appreciate it. This is more than enough to pass this exam with a similar score of mine.
There are quite lot of short wordings used here only to reduce the time you might take to read this. You will have no problems in understanding this if you have a reasonably good networking knowledge.
Ramesh’s Study Guide
OSI Layers: It allows changes in one layer to occur without changing other layers, It clarifies what general function is to be done rather than how to do it.
Application –file, print, message, database, application svcs. identifying communication partners, determining resource availability, and synchng sending & receiving applictns, Eg: SMB, NCP, Telnet, FTP, WWW and SMTP, File Transfer Access and Mangt (FTAM), Virtual Term Proto (VTP), and Common Mangt Info Proto (CMIP).
Presentation-Negotiating data xfer Syntax, Data encryption, compression, translation, coding and conversion functions. Eg. ASCII, EBCDIC, JPEG, GIF, TIFF, MPEG, PICT, MIDI, QuickTime,
Session?u>Dialog Control-establishes, manages, maintains, and terminates sessions between applications, communication sessions consist of service requests and service responses that occur between applications located in different network devices. Eg. NFS (sun), SQL, RPC, X window, ASP, Zone Info Proto (ZIP), and Session Control Proto (SCP).
Transport-End-End conn, hides info from upper layer, gives transparent data transfer, segments and reassembles data into data streams. responsible for both reliable and unreliable end-to-end logical conn. does flow control, windowing, acknowledgement, multiplexing, virtual circuit management, session establishment and error checking and recovery.
Eg. TCP, UDP, SPX, Name Binding Protocol (NBP), Nwlink, NetBeui, ATP, NBP.
Network-Routing-uses logical addressing to provide routing and related functions that allow multiple data links to be combined into an internetwork. supports both connection-oriented and connectionless service from higher-layer protocols. protocols are typically routing protocols. BGP, OSPF, DLC, DecNet, ICMP, RIP, NLSP, IGRP, EIGRP, Packets and datagrams are sent across this layer.
Data Link-Framing-putting 1’s & 0’s in to a logical group, provides reliable transmission of data across a physical medium. specifies different network and protocol characteristics, including physical addressing, network topology, error notification, sequencing of frames, and flow control. two sublayers known as the Media Access Control (MAC) and the Logical Link Control (LLC) layer. LLC- Provides flexibility to upper & lower protos. Respon timing, flow control, supports both conn less & conn oriented svcs used by upper protocols. MAC-respon for framing, access to physical net media.Eg. ARP. DLL implementations are LAN or WAN specs. LAN imples- Ethernet/IEEE 802.3, Fast Ethernet, FDDI, and Token Ring/IEEE 802.5,WAN imples.-Frame Relay, LAPB, SDLC, HDLC, X.25, SLIP, PPP.
MAC Add. : 6 bytes ( 3 bytes- vendor code, 3 bytes- Serial No.)
Ethernet_II -PreAmb8-DA6-SA6-Type2(upper layer proto ID)-Data-FCS 4 (Cyclic Redundancy Checksum).
802.2_Ethernet-PreAmb8-DA6-SA6-Length-DSAP-SSAP(802.2 LLC header)-Data-FCS.(MAC & LLC)
802.3_Ethernet-PreAmb8-DA6-SA6-Length-Data-FCS (MAC) (CSMA/CD-IEEE-802.3) can’t identify up layer protos.
Physical-defines Bit synch & Physical topology, Specs define such as voltage levels, timing of voltage changes, physical data rates, max trans distances, and the physical conntrs be used. Eg. FDDI, SONET, ISDN. (Stds: v.24, v.35, x..21, G.703 ), LAN-imples-Ethernet/IEEE 802.3, Fast Ethernet, FDDI, and Token Ring/IEEE 802.5.
WAN-imples- High-Speed Serial Interface (HSSI), SMDS Interface Protocol (SIP), and X.21bis.
10Base2-ThinNet-RG58-BNC-185 Mtrs, 100BaseT4-100MB,Cat 3/4/5, 802.3
10Base5-ThickNet-RG8-DIX/AUI-500Mts, 100 BaseTx-Cat5-STP-100 Mtrs.(Fast Enet over STP/802.3),
10BaseT-Cat3/4/5-100Mts. 100Base Fx-100MB,2 pr OFC 802.3
10/100Base FL-OFC-2 Km, 100Base VG Any LAN-OFC, 802.3 ( Cisco does not support it)
100BaseT- CSMA/CD, 802.3u, Fast Enet,
DOD Model : Proc / Appl : Telnet, FTP, LPD SNMP/ FTP, SMTP, NFS, X window, Host-Host : TCP,UDP,
Internet : ICMP, BootP, ARP, RARP/IP, Net Acc : Ether Net, Fast Enet, Token Ring, FDDI.
Tcp/udp: port Nos. 0-255:used for public appl, 255-1023: for comp to use their appl; >1023 for upper layers sessions with other Hosts. Tcp : virtual ckt, conn oriented, sequenced, ackd, reliable, high o/h, Udp: unsequenced, unreliable, connless, low o/h. ftp>tcp21, telnet>tcp23, smtp>tcp25, tftp>udp69, snmp>udp161, tcp>ip6, udp>ip17
Data Flow : User info is converted to Data(7,6,5), Data converted to Segments(4), Segments converted to Packets or datagrams(3), Packets and datagrams are converted to frames(2), Frames are converted to bits(1).
ICMP Inet Contr Mess Proto: Alerts routers if : Destn unreach, Buffer full, Hops-demise, ping uses ICMP+IP,
sends redirects back to origi router. SNMP: Simple Net Mngmt Proto- used to manage & Monitor Net,
RARP server- gives IP add against MAC add to diskless comp, BootP- gives IP add & boots diskless comp/w stns.
ARP- layer3 proto, Source & Destn H/w add keeps changing, but IP add remains same as pkt travels thro?routers.
LAN Segmentation: breaking up the collision domains by decreasing the number of workstations per segment.
Full Duplex Ethernet : needs full duplex NIC cards, Loop back and collision disabled, 2 x 10/100 MB paths, software driver supporting two simultaneous data paths, Adherence to Enet Stds.
Fast Ethernet (100MB)- provides 10 times the bandwidth of older 10bastT Ethernet. Must have Cat5 cable, no longer than 100 meters, and Fast Ethernet NIC’s and Hubs/Switches.
Gateway?/b>used for comm between diff NOS Eg. NT & IBM SNA,takes the pkt strips off the old protocol and repackages for the receiving network- proto translation (Trans, sessio, prestn, appli).
Router-Filters by both HW add & IP add. strip off data link sourc & dest add & recreates it. Provides flow control, manageability, Explicit pkt life time control, more functionality, multi paths, segments net, links unlike phys media, stops broadcasts, no un routable Net protos , Brouter- will act as router and bridge based on protocols. (DLL, Network).
Bridge-Segs net, filters traff by MAC add, regenerates signal at pkt level, reliability, availability, scalability, manageability, latency, pass broadcasts, no unlike med (DLL,mac sub). Switch-Duplex, filters trafiic on MAC add, pass broadcasts, (DLL) Repeater- regenerates signals for tx, pass broadcasts, no unlike phys media. (Physical).
Hubs- one tx, all other rx, simplex, no addressing(Physical).Multiplexer- for multiplexing links.(Physical)
Repeater reduces dist for 100BaseFx due to delays, but extends 100BaseTx dist. Class1:Translational rptr supports both 100baseX and 100baset4 signalling. Delay=140 bit times, Class 2:Transparent rptr only supports either 100baseX or 100baseT4, not both at same time.delay=92 bit times. FastHub300: Rptr compatible with 802.3u for fast Enet.
LAN Switching : Uses dest MAC add to forwd pkts. same as multi port Bridge. Multi simultaneous convs, high speed data exges, low latency & high frame fowd rates, full duplex, media rate adaption (10/100). Port Switching: port assigned to a phys net by software. Frame Switching: increases b/w on the net. Allows multi trans in parallel. used in Cisco Cata switch. Cell Switching: ATM. Uses small fixed length cells that are switched on the net. Used in Cisco light stream switches.
Router Switching : Store & Forward: copies entire frame in to buffers and checks CRC. Forwards 64-1518 Bytes only. latency high depends on Frame Length. used in cat 05000/5505 series. Cut-through (Real Time): copies only dest add (6B) in to buffers. some switches automly uses both modes, Low latency, 10/100mb full duplex Fragment Free: modified cut thro. Waits for collision window (first 64 B). Better error checking, no latency.
Spanning-Tree Protocol (STP) IEEE 802.1d- to prevent routing loops. STA (Spanning-Tree Algorithm) is impled by STP to calculate a loop-free net topology. In Cat 5000 based nets Bridge proto data units (BPDU) are sent & recd by all switch in regular intervals & processed to determine spanning-tree topology.
Virtual LAN’s-have diff ports of a switch be parts of diff sub nets. can be by location, function, grp & dept. Simplify moves, adds, changes. less admn costs, better control of broadcasts, tighten net security, distribute load, Relocate server into secured locations. Frame tagging: A user defined ID for each frame, places a unique user defined ID in the header of each frame used within switch fabric itself. Used in Cat 3000 & 5000 series. Developed for multi VLAN, Inter switch Commn, needs processor & admn load.
IP Address Classes:
(2)192-2-4194302-16382-62 Class A Net.Node.Node.Node 0 1-127 127 net 16777214 nodes
(3)224-6-2097150-8190-30 Class B Net.Net.Node.Node 10 128-191 16384 net 65534 nodes
(4)240-14-1048574-4094-14 Class C Net.Net.Net.Node 110 192-223 2097152 net 254 nodes
(5)248-30-524286-2046-6 (net/node all 0-this net/node, all 1-all net/node) (127-loopback add )
(6)252-62-262142-1022-2 (entire IP all 0-cisco default route, all 1-broadcast to all nodes)
(7)254-126-131070-510-na Max # of Subnets: 2(masked bits)-2, Max # of Hosts / subnet : 2(unmasked bits)-2
(8)255-254-65534-254-na Class D-224-239-Multicasts, Class E- 240-255-Future.
Directed / only subnet broadcast add- 172.16.3.255, Flooding / total Network broadcast add- 172.16.255.255
Cisco Routers :
2500 : Cons port- async serial port RJ45 60 Pins, Aux port- Modem RJ45,Telnet port - Ethernet 0, (S0,S1-serial port), External ports - TFTP server, Virtual Term, Net Mngmt Stns. ROM-holds Bootstrap Startup programs, OS software, POST. Flash-EEPROM-holds cisco IOS image and Microcode, RAM-holds running OS, running config, provides caching & pkt filtering. NVRAM-Stores startup config, config mem: executes NVRAM commands, copies start to Run,
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