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CCNA (Cisco Certified Network Associate) (1) CCNA 640-801 (2) --Cisco IOS Software Fundamental --OSI Reference Model and Layered Communication --LAN Protocol, Bridges, Switches, Spanning Tree, VLANs,

1 CCNA (Cisco Certified Network Associate) (1) CCNA (2) --Cisco IOS Software Fundamental --OSI Reference Model and Layered Communication --LAN Protocol, Bridges, Switches, Spanning Tree, VLANs, and Trunking --TCP/IP, IP Routing, and Routing Protocol --WAN Protocols and Design --Novell IPX -- xams/ html (3) 90 ( ) 4 (1) (Protocol) -- IEEE) ISO IETF -- FTP HTTP SMTP POP (2) RFC (Request For Comment) -- IETF IESG Internet RFC --RFC (3) (Topology) (Bus) (Star) (Ring) 1

2 (4) (Client/Server architecture) -- Outlook Express (Client) HINet (Server) (5) (Peer-to-Peer mode) -- edonkey Kuro (6) --IP address & MAC address (7) -- 0, , 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F -- (8) (Firewall) Public Private DMZ Internet Public Firewall Private ( ) DMZ Web server Mail server (9) --SNMP (Simple Network Management Protocol) -- Station Agent --MIB (Management Information Base) --SNMP MRTG HP OpenView -- Community Name -- Polling Trap Network Management Station Network Agent Agent MIB 1 MIB 2 (10) 2

3 (LAN) (1) (2) -- (Ethernet) (3) ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) (Half-Duplex) -- (Full-Duplex) (4) (Collision) -- --IEEE802.3 CSMA/CD(Carrier Sense Multiple Access Collision Detect) 3

4 ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) IEEE802.3 CSMA/CD (Hub) 4

5 ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) (5) --MAC address 48bits 24bits (OUI) 24bits Unicast Multicast Broadcast (6) Ethernet Ethernet (DIX) Variable 4 Preamble Dest. Source Type Data FCS Address Address IEEE Ethernet Variable 4 Preamble SD Dest. Address Source Address Length D S A P S S A P Control Data FCS IEEE Ethernet Variable 4 Preamble SD Dest. Address Source Address Length D S A P S S A P Control SNAP Data FCS

6 (Bridge) -- (MAC Address table) Broadcast Multicast Unicast -- Spanning Tree Protocol ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) 6

7 (Switch) (1) -- ASICs (Application-specific integrated circuits) -- (MAC Address table) -- Port -- Broadcast Multicast Unicast Switch Port -- Spanning Tree Protocol Port -- VLAN (Virtual LAN) (2) ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) 7

(3) Switch ( Cisco CCNA Exam#640-607 Certification Guide, Odom, Cisco Press) Collision domain Broadcast domain --Collision domain ( ) A collision domain is a set of network interface cards (NICs) for

8 (3) Switch ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) Collision domain Broadcast domain --Collision domain ( ) A collision domain is a set of network interface cards (NICs) for which a frame sent by one NIC could result in a collision with a frame sent by any other NIC in the same collision domain. --Broadcast domain ( ) A broadcast domain is a set of NICs for which a broadcast frame sent by one NIC will be received by all other NICs in the broadcast domain. Bridge Switch Router 8

9 ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) Bridges, Switches, and Routers ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) Q&A (1) (Hub Switch) (2) (Hub Switch) (3) VLAN 9

10 OSI TCP/IP (1) ISO OSI (Open System Interconnection, OSI) (International Standard Organization, ISO ) 1978 Application) (Presentation) (Session) (Transport) (Network) (Data Link) (Physical) OSI (2) -- Humans can more easily discuss and learn about the many details of a protocol specification. -- Standardized interfaces among layers facilitate modular engineering. Different products can provide functions of only some layers (such as a router with Layers 1 to 3), or some products could supply parts of the functions of the protocol (such as Microsoft TCP/IP built into Win95, or the Eudora application providing TCP/IP application layer support). -- A better environment for interoperability is created. One vendor can write software that implements higher layers for example, a Web browser and another can write software that implements the lower layers for example, Microsoft s built-in TCP/IP software in its operation systems. -- Reduced complexity allows easier program changes and faster product evolution. -- One layer uses the services of the layer immediately below it. Therefore, remembering what each layer does is easier. (For example, the network layer needs to deliver data from end to end. To do this, it uses data links to forward data to the next successive device along that end-to-end path.) ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) 10

11 (3) OSI 11

12 ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) 12

13 (4) (Encapsulation) Application L7H Data Presentation L6H Data Session L5H Data Transport L4H Data Network L3H Data Data Link L2H Data FCS Physical Bits send or receive. ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) (5) Transport Layer Network Layer Data Link Layer Transport Layer Network Layer Data Link Layer Windowing 13

14 TCP/IP (Transmission Control Protocol/ Internet Protocol) (1) OSI TCP/IP OSI Application ( ) Presentation ( ) Session ( ) TCP/IP Application Transport ( ) Transport (TCP UDP) Network ( ) Internet (IP ARP ICMP) Data link ( ) Physical ( ) Network Access (2) TCP/IP -- ICMP (Internet Control Message Protocol) ICMP Message Destination Unreachable Purpose This tells the source host that there is a problem delivering a packet. Network unreachable (sent by Router) Host unreachable (sent by Router) Can t fragment (sent by Router) Protocol unreachable (sent by Host) Port unreachable (sent by Host) Time Exceeded The time that it takes a packet to be delivered has expired; the packet has been discarded. Ex: 14

15 Source Quench Redirect The source is sending data faster than it can be forwarded; this message requests that the sender slow down The router sending this message has received some packet for which another router would have has a better route; the message tells the sender to use the better route. Ex: Echo Timestamp This is used by the PING command to verify connectivity. This is used to measure round-trip time to particular hosts. ( Cisco CCNA Exam# Certification Guide, Odom, Cisco Press) -- ARP (Address Resolution Protocol) ARP: IP address MAC address. Reverse ARP: MAC address IP address. Proxy ARP: MAC address IP address -- TCP (Transmission Control Protocol) Multiplexing Socket Socket IP address Transport protocol Port number 15

16 Error recovery (Reliability) (Acknowledgment) Flow control using windowing Sliding Window 16

Connection establishment and termination TCP -- (Three-way handshaking) TCP Ordered data transfer -- UDP (User Datagram Protocol) --UDP TCP Function Description(TCP) Description(UDP) Data transfer

17 Connection establishment and termination TCP -- (Three-way handshaking) TCP Ordered data transfer -- UDP (User Datagram Protocol) --UDP TCP Function Description(TCP) Description(UDP) Data transfer Multiplexing Reliable transfer This involves a continuous stream of ordered data. Receiving hosts decide the correct application for which the data is destined, based on the port number. Acknowledgment of data uses the sequence and acknowledgment fields in the TCP header. This involves message (datagram) delivery. Receiving hosts decide the correct application for which the data is destined, based on the port number This is not a feature of UDP. 17

18 Flow control Connections This process is used to protect buffer space and routing devices. This process is used to initialize port numbers and other TCP header fields. This is not a feature of UDP. UDP is connectionless. --DHCP (Dynamic Host Configuration Protocol) DHCP server IP address DHCP discover (broadcast) DHCP offer (IP, DNS, lease time) DHCP request (include IP that DHCP server provided) DHCP ACK --DNS (Domain Name System) DNS Root tw cn uk com edu gov org net pccu ncku tku www ftp cs www w Domain w Host IP address IP address Whois ( nslookup 18

19 Q&A (1) (NIC) (2) (Switch) (3) (Hub) (4) (Router) (6) (domain name) (7) ( A. TCP (Three-way Handshaking) B. TCP (FIN ACK) C. (8) NAT (Network Address Translation) router NAT Router 19

20 IP IP address (Host address) Network Network number (Network address) Broadcast address Network mask ( ) 32bits IP address (NIC) A group of hosts, all of which have an identical beginning portion of their IP addresses. A 32-bit number, usually written in dotted-decimal form that represents a network. This number cannot be assigned as an IP address to an interface of any computer. The host portion of the network number has a value of all binary 0s. A 32-bit number, usually written in dotted-decimal form that is used to address all hosts in the network. This number cannot be assigned as an IP address to an interface of any computer. The host portion of the network number has a value of all binary 1s. A 32-bit number, usually written in dotted-decimal form. The mask is used by computers to calculate the network number of a given IP address by performing a Boolean AND of the address and mask. The mask also defines the number of host bits in an address IP --Class A, Class B, Class C bits Class A Network (8) Host (24) Class B Network (16) Host (16) Class C Network (24) Host (8) Class A Class B Class C Number of network bits Number of host bits First octet start with

21 First octet range 1 to to to 223 Valid network numbers to to to Total number of this 2 7, minus , minus , minus 2 class of network Number of host 2 24, minus , minus 2 2 8, minus 2 addresses per network Default network mask (1) Subnetting -- Class A, Class B, or Class C -- IP -- Host ID Bit Network ID (2) Subnet mask ( ) -- Network mask (3) / / / / /27 Mask Number of network bits Number of host bits Number of subnet bits Number of hosts per subnet Number of subnets Subnet number First valid IP address Broadcast address Last valid IP address

22 Private address (1) IP Internet (2) Private IP (3) RFC1918 Private IP address Range of IP Address Class of Network Number of Network to A to B to C 256 IP Routing (1) Routing Protocol and Routed Protocol --A routing protocol fills the routing table with routing information. Examples include RIP and IGRP. --A routed protocol is a protocol that has an OSI Layer 3 equivalent specification that defines logical addressing and routing. Examples of protocols include IP and IPX. (2) Convergence time ( ) --The time required for routers to react to changes in the network, removing bad routes and adding new, better routes so that the currently best routes are in all the routers routing tables. (3) --Static route --Dynamic route Routing protocol --Default gateway Routing table Default gateway Routing protocol (1) Routing protocol --To dynamically learn and fill the routing table with a route to all subnets in the network. --If more than one route to a subnet is available, to place the best route in the routing table. --To notice when routes in the table are no longer valid, and to remove those routes from the routing table. --If a route is removed from the routing table and another route through another neighboring router is available, to add the route to the routing table. 22

23 --To add new routes, or th replace lost routes with the best currently available route, as quickly as possible. The convergence time should be short. --To prevent routing loops. (2) RIP (Routing Information Protocol) --A Distance-Vector routing protocol -- Broadcast(RIP v1) Multicast(RIP v2) -- Hop-count(Metric) Router (Maximum Metric is 15) -- Routing table Metric=16 -- Router Router B Router A Router B Destination Outgoing Interface Next-Hop router Metric S E0 N/A S0 N/A S S

24 (3) RIP Issue Multi routes to the same subnet have equal metrics Routing loops occur due to updates passing each other over a single link Solution Implementation options involve either using the first route learned or putting multiple routes to the same subnet in the routing table. Split horizon The routing protocol advertises routes out an interface only if they were not learned from updates entering that interface. Split horizon with poison reverse The routing protocol uses split-horizon rules unless a route fails. In that case, the route is advertised out all interfaces, but with infinite-distance metrics (Metric=16). 24

25 Routing loops occur due to updates passing each other over alternative paths Counting to infinity Route poisoning When a route to a subnet fails, the subnet is advertised with an infinite-distance metric. Hold-down timer After finding out that a route to a subnet has failed, a router waits a certain period of time before believing any other routing information about that subnet. Triggered updates When a route fails, an update is sent immediately rather than waiting on the update timer to expire. Used in conjunction with route poisoning, this ensures that all routers know of failed routes before any hold-down timers can expire. Q&A (1) ISP ADSL (2) IP Internet (3) ISP Subnet mask Router WAN Interface 25

26 (1) Synchronous --The imposition of time ordering on a bit stream. Even if there is no data to be sent, synchronous link will send idle frames for clock adjustment. --For examples, LAPB, HDLC, or PPP. (2) Asynchronous --The lack of an imposed time ordering on a bit stream. However, because only 1 byte per transfer is sent, slight difference in clock speed is not an issue. --For examples, ATM or PPP. (3) Clock source --The device to which the other devices on the link adjust their speed when using synchronous links. (4) DSU/CSU --Data Service Unit/Channel Service Unit. Routers typically use a short cable from a serial interface to a DSU/CSU, which is attached to the line from the telco with a similar configuration at the other router on the other end of the link. The routers use their attached DSU/CSU as the clock source. (5) DTE/DCE cable connector --The DCE (Data Communications Equipment) cable has a female connector, and the DTE (Data Terminal Equipment) has a male connector. --The DCE connector is attached to the device with clock source. Point-to-Point Protocol (PPP) (1) OSI Layer 2 (2) PPP Link Control Protocol (LCP) 26

27 -- Error detection, Looped link detection, Authentication, Compression, and Multilink support Point-to-Point Protocol over Ethernet (PPPoE) (1) ADSL PPPoE (2) PPPoE Discovery PPP session (3) Discovery stage PADI (include service name or not) PADO PADR PADS (include session number) 27

28 PPP session stage PPP LCP request (MRU) ACK (or NAK) PPP LCP request (Authentication type) ACK (or NAK) PPP PAP authenticate ACK (or NAK) PPP IPCP request (server s IP) ACK PPP IPCP request (client s IP: or designated IP) NAK (provide IP to client) or ACK PPP IPCP request (include IP that server provided) ACK Integrated Services Digital Network (ISDN) (1) ISDN interfaces --BRI: Basic Rate Interface --PRI: Primary Rate Interface Type of Interface Number of Bearer Channels (B channels) Number of Signaling Channels (D channels) BRI 2 1 (16 kbps) PRI (T1) 23 1 (64 kbps) PRI (E1) 30 1 (64 kbps) (2) ISDN protocols 28

29 (3) ISDN Function Groups and Reference Point --Function group: A set of functions implemented by a device and software. --Reference point: The interface between two function groups, including cabling details. Frame Relay (1) Frame Relay Components 29

30 Term Virtual circuit (VC) Permanent virtual circuit (PVC) Switched virtual circuit (SVC) Data-link connection identifier (DLCI) Data terminal equipment (DTE) Data communications equipment (DCE) Access link Local Management Interface (LMI) Access Rate (AR) Committed information rate (CIR) Committed Burst (BC) Description A logical concept that represents the path that frames travel between DTEs. A predefined VC. A PVC can be equated to a leased line in concept. A VC that is set up dynamically when needed. A Frame Relay address used in Frame Relay headers to identify the VC. DTEs are connected to a Frame Relay service from a telecommunications company and typically reside at sites used by the company buying the Frame Relay service. Frame Relay switches are DCE devices. DCEs are typically in the service provider s network. The leased line between DTE and DCE. The protocol used between a DCE and DTE to manage the connection. Signaling messages for SVC, PVC status messages, and keep-alive are all LMI messages. The speed at which the access link is clocked. The rate at which the DTE can send data for an individual VC, for which the provider commits to deliver that amount of data. BC defines the number of bits that can be sent consecutively at Access Rate. (3) LMI and Encapsulation types --DTE DCE LMI type LMI Type Document IOS LMI-Type Cisco Proprietary cisco ANSI T1.617 Annex D ansi ITU Q.933 Annex A q933a -- VC DTEs Frame Relay (cisco or ietf) 30

31 (4) DLCI --The sender treats the DLCI field as a destination address, using the destination s global DLCI in the header. --The receiver thinks of the DLCI field as the source address, because it contains the global DLCI of the frame s sender. (5) Frame Relay --Full mesh: DTE 31

32 --Partial mesh: DTE DTE --Hybrid mesh: Full mesh Partial mesh Type of WAN Service Leased line Data-Link Protocol PPP Strengths and Weaknesses Provides dedicated bandwidth. Can be expensive for long circuits. Can improve the speed of routing protocol convergence. Allows multi-vendor interoperability. Has error-recovery option. 32

33 Packet-switched HDLC The Cisco IOS software default. Requires a Cisco router on each end. LAPB Provides error recovery, but this can result in slowing the data rate. Allows new sites to be added quickly. Typically involves a lower cost. Frame Relay Allows bursting past CIR, giving the perception of free capacity. Is pervasive in the USA. ATM As a WAN technology, is not as pervasively available as Frame Relay. Has an attractive built-in Quality of Service(QOS) feature. X.25 Is available pervasively in some parts of the world. Offers beneficial error-recovery features when links have higher error rates. Q&A (1) PAP CHAP (2) Frame Relay Full mesh, Partial mesh, or Hybrid mesh 33

34 Cisco IOS IOS (Internetworking Operating System) IOS Cisco Router Switch Cisco Router IOS Cisco router (1) RAM Sometimes called DRAM for dynamic random-access memory, RAM is used by the router just as it is used by an other computer: for working storage. The running or active configuration file is stored here. (2) ROM This type of memory (read-only memory) stores a bootable IOS image, which is not typically used for normal operation. ROM contains the code that is used to boot the router until the router knows where to get the full IOS image, or as a backup bootable image in case there are problems. (3) Flash memory Either an EEPROM or a PCMCIA card, Flash memory stores fully functional IOS images and is the default location where the router gets its IOS at boot time. Flash memory also can be used to store configuration files on some Cisco routers. (4) NVRAM Nonvolatile RAM stores the initial or startup configuration file. Cisco IOS (1) The router performs a power-on self-test (POST) to discover and verify the hardware. (2) The router loads and runs bootstrap code from ROM. (3) The router finds the IOS or other software and loads it. The full-function IOS which is stored in flash typically. A limited-function IOS. Basic IP connectivity, used when flash memory is broken and you need IP connectivity to copy a new IOS into flash memory. Called RXBOOT mode. Non-IOS operation system, called ROM Monitor (ROMMON mode), is used for two purposed: for low-level debugging and for password recovery. (4) The router finds the configuration file and loads it into running config. Find start-up config in NVRAM and copy it to running config. If NVRAM is empty, then enter in setup mode. 34

35 Setup mode 35

36 36

37 Cisco IOS command-line interface (1) IOS CLI -- Cisco Router (Telnet) Auxiliary port Console port CLI Cisco router -- Config mode (User mode) A. CLI > B. Router C. 37

38 (Privileged mode) A. Enable mode # B. Router Log C. D. Router TFTP server RAM NVRAM (Configuration mode) A. Router B. C. Command Global command Subcommand D. Running config Start-up config Router (2) IOS CLI Help 38

39 (3) IOS Syslog and debug --Syslog -- Debug Router Debug Router Router (4) IOS CLI user mode enable mode enable mode user mode enable mode config mode config mode enable mode Running-config Startup-config Router enable, may need password disable configure terminal exit, or Ctrl+Z show running-config show startup-config hostname 39

40 prompt xxx Enable mode enable password xxx enable secret xxx Console connection line console 0 login passwd xxx Auxiliary connection line aux 0 login passwd xxx Telnet connection line vty 0 4 login passwd xxx Interface serial 1 interface serial 1 RIP IP host table description this is a WAN connection ip address no shutdown router rip network x.x.x.x ip host router_name router_ip1, Clock clock rate router_ip2,.. 40

工程师培训

工程师培训 .1 TCP/IP TCP/IP 1 .2.2.1 Host 1960 S 1970 S Host Low Speed Lines 1970 S 1980 S pc Server Local Interneting 1980 S 1990 S Branch. pc Branch. WAN Branch. pc pc IBM SNA IBM X.25 2 .2.2 OSI OSI Application