OSI Reference Model It is a layered model consisting of seven layers. Layers of OSI Model Application: Provides network access for applications, flow control and error recovery. Use protocols like NCP, SMB, SMTP, FTP, SNMP, Telnet, and AppleTalk. Presentation: Performs protocol conversion, encryption and data compression. Use the protocols like NCP, AFP, and TDI. Session: Allows 2 applications to communicate over a network by opening a session and synchronizing. Protocol used NetBIOS. Transport: Repackages messages into smaller formats, provides error free delivery and error handling functions. Use the protocols like NetBEUI, TCP, SPX, and NWLink. Network: Handles addressing, translates logical addresses and names to physical addresses. Use the protocols like IP, IPX, NetBEUI and device used is Router. Data Link: Packages raw bits into frames and includes a cyclical redundancy check. Consists of the LLC sublayer and the MAC sublayer. MAC sublayer is responsible for appending the MAC address of the next hop to the frame header. LLC sublayer uses Destination Service Access Points and Source Service Access Points to create links for the MAC sublayer. The device like Switch, bridge and brouter works on this layer. Physical: Works with the physical media for transmitting and receiving data bits. Multiplexer and repeater are used at this layer. MAC Address: It’s a 48 bit address for uniquely identifying devices on the network. This is a way of presenting the address a 12 hexadecimal digits format. First 6 digits specify the manufacture. Local Area Networks Ethernet: Ethernet is a physical layer LAN technology, created by Digital Intel Xerox (DIX). Information for configuring an Ethernet as defined in 802.3. Half-duplex Ethernet: Use separate circuits for transmitting and receiving data and as a result, collisions are largely avoided. For full-duplex transmission, a switch port and NICs that are capable of handling full duplex is required. Fast Ethernet: For networks that need higher transmission speeds. Based on IEEE 802.3u that raises the Ethernet speed limit to 100 Mbps. 10BaseT network use Cat3 cable and 100BaseT network need Cat 5 cables. The three types of Fast Ethernet standards are 100BASE-TX for use with level 5 UTP cable, 100BASE-FX for use with fiber-optic cable, and 100BASE-T4 required an extra two wires for use with level 3 UTP cable. Gigabit Ethernet: Provide transmission speeds of 1000mbps. It uses Ethernet frame format, full-duplex and media access control technology. Token Ring: An older standard, with transmission rates of either 4 or 16mbps. Token passing is the access method used by token ring networks, whereby, a 3bit packet called a token is passed around the network. FDDI: It can transmit both asynchronous as well as synchronous data. FDDI Physical Parameters: Media: 1300nm, optical fibers, Transmission Method: Baseband, Data Rate: 100Mbps, Topology: physical ring of trees, logical ring, And Maximum distance between adjacent stations: 2 km, Total max. ring length: 100 km.

FDDI uses two counter rotating rings i.e. Primary Ring and Secondary Ring. Secondary ring can be used either as an additional transmission path or purely as a backup in the event of a break occurring in the primary ring. Network Devices Hub: Repeats signals received on each port by broadcasting to all the other connected ports. Repeaters: Use to connect two or more Ethernet segments of any media type, and to provide signal amplification for a segment to be extendeds. Bridge: It’s a layer 2 device used to connect different networks types or networks of the same type. Maps the Ethernet addresses of the nodes residing on each segment and allows only the necessary traffic to pass through the bridge. Switch: It’s a layer 2 devices and use for linking the networks. Available in two types i.e. Cut-through switches and store-and-forward switch. Cut-through switches forwards it right after looking at the destination address only and store-and-forward switch inspects the entire packet before forwarding. Routers: Filter out network traffic. Protocols must be routable in order to pass through the routers. Also determine the most efficient path for a packet to take and send packets around failed segments. Brouter: The best features of routers and bridges in that it can be configured to pass the non-routable protocols. Gateway: Used as a connection to a mainframe or the internet. Enable communications between different protocols, data types and environments. Operate at all layers of the OSI model. LAN Protocols TCP/IP: IP address can be broken down into 2 parts, the Network ID and the Host ID. All hosts on the same network must have the same Network ID. IP addresses are divided into 4 octets with each having a maximum value of 255. IP addresses can be class A, B or C. Class A addresses for networks with a large number of hosts. Class B addresses are used in medium to large networks with the first 2 octets making up the Network ID and the remaining 2 are the Host ID. A class C is for smaller networks with the first 3 octets making up the Network ID and the last octet comprising the Host ID. Class A is having default subnet mask 255.0.0.0 with a total of 126 subnets and 16,777,214 hosts per subnet. Class B is having default subnet mask 255.255.0.0 with a total of 16,384 subnets and 65,534 hosts per subnet. Class C is having default subnet mask 255.255.255.0 with a total of 2,097,152subnets and 254 hosts per subnet. TCP/IP Ports: An application uses ports for communicating between a client and server. Common TCP/IP ports are: 20 FTP-DATA, 21 FTP, 23 TELNET, 25 SMTP, 69 TFTP, 70 GOPHER, 80 HTTP, 110 POP, 3137 NetBIOS name service, 138 NetBIOS datagram service, 139 NetBIOS161 SNMP. Spanning-Tree Protocol: Allows duplicate switched/bridged paths without incurring the latency effects of loops in the network. Spanning-Tree Algorithm: Implemented by the Spanning-Tree Protocol prevents loops by calculating stable spanning-tree network topology. IPX/SPX: Two parts of IPX Network address - the Network ID and the Host ID. The first 8 hex digits represent the network ID, while the remaining hex digits represent the host ID, which is most likely the same as the MAC address. Sequenced Packet Exchange (SPX) belongs to the Transport layer, and is connection-oriented.

Creates virtual circuits between hosts, and that each host is given a connection ID in the SPX header for identifying the connection. WAN Technology Three types of WAN access technology: point-to-point dedicated connection, Circuit Switching, Packet Switching. Frame Relay: Successor to X.25 and relies on upper layer protocols to perform error checking. Its speed in between the range of 56 Kbps to 2.078 Mbps. Uses Data Link Connection Identifiers(DLCI) to identify virtual circuits with number between 16 and 1007. Transfer data with permanent virtual circuits and can use switched virtual circuits as well. Data Link Connection Identifier Bits (DLCI): Used to identify the virtual connection. DLCI has only local significance. ISDN: Works at the Physical, Data Link, and Network Layers. Based on Dial on Demand Routing and supports simultaneous data and voice with a speed at 125 Kbps with PPP Multilink. BRI has 2 x 64 1Kbps B Channels for data and one 16 Kbps D Channel for control where as PRI has 23 x B Channels and one D Channel in the US, or 30 x B Channel and one D Channel in Europe. Required Terminal Adapter TA to use TE2. ATM: Stands for Asynchronous Transfer Mode and is a high-speed, packet-switching technique. Transmit voice, video, and data over a variable-speed LAN and WAN connections at speeds ranging from 1.544Mbps to as high as 622Mbps. ATM cell identifiers: Virtual Path Identifier (VPI), Virtual Channel Identifiers (VCI) and Payload Type Identifiers (PTI). PPP: Consider it as an improvement to Serial Line Internet Protocol (SLIP). It was mainly for the transfer of data over slower serial interfaces. Provides multiprotocol support, error correction as well as password protection. It is a Data Link Layer protocol used to encapsulate higher protocols to pass over synchronous or asynchronous communication lines. Also capable of operating across any DTE/DCE device. PAP: Similar to a network login but passwords are sent as clear text and used on FTP sites. CHAP: Uses encryption and is a more secure way of sending passwords. Point-to-Point Tunneling Protocol(PPTP): Provide for the secure transfer of data from a remote client to a private server by creating a multi-protocol Virtual Private Network(VPN) by encapsulating PPP packets into IP datagram’s.

VLAN It’s a logical grouping of devices or users. Configuration is done at the switch via switching fabric. Create separate broadcast domains in a switched network. Use layer 2 addressing and routers are required between separate VLAN’s. Layer 3 routing provides the ability for multiple VLAN’s to communicate with each other. Configured on the switch in three ways, port centric, static, and dynamically. Port-centric VLAN’s: Nodes connected to ports in the same VLAN are assigned the same VLAN ID. Static VLAN’s: Use the port centric method for assigning them to switch ports. Dynamic VLAN’s: Ports on a switch that can automatically determine their VLAN assignments. Functions are based on MAC addresses, logical addressing, or protocol type of the data packets. Copyright Train Signal, Inc., 2002-2005

Introduction to IOS Internetworking Operating System is stored in flash and configuration information is stored in Non-Volatile RAM. Telnet, console connection or dial in connection are used to access IOS. Sources for booting IOS includes Flash memory, TFTP and ROM. Booting command boot system flash {filename}, boot system tftp {filename} {tftp server IP address}, boot system rom. User EXEC is the first mode after booting of a router with a prompt of "Router>". Next is Privileged EXEC mode with a prompt “Router#" This mode includes support for all commands in user mode plus those that provide access to global and system settings. Setup command facility is for making major changes to the existing configurations, such as adding a protocol suite, modifying a major addressing scheme changes. Type in a”?” mark to display a list of commands available for each command mode. Editing Commands Crtl-P: Recall commands in the history buffer starting with the most recent command. Crtl-N: Return to more recent commands in the history buffer after recalling commands the up arrow key. Crtl-B: Move the cursor back one character. Crtl-F: Move the cursor forward one character. Crtl-A: Move the cursor to the beginning of the command line. Crtl-E: Move the cursor to the end of the command line. Esc B: Move the cursor back one word. Esc F: Move the cursor forward one word. Crtl-R: Redisplay the current command line. Access Lists Use to implement security on the network by inspecting and filtering traffic as it enters or exits an interface. Router can have many access lists of the same or different types. Two major types of access lists: IP Access Lists and the IPX Access Lists. Type Of Access lists with Numbers: 1-99: Standard IP, 100-199: Extended IP, 200-299: Protocol type-code, 300-399: DECnet, 600-699: Appletalk, 700-799: Standard 48-bit MAC Address, 800-899: Standard IPX, 900-999: Extended IPX, 1000-1099: IPX SAP, 1100-1199: Extended 48-bit MAC Address, 1200-1299: IPX Summary Address

Routing Routing is the act of moving information across an internetwork from a source to a destination and routing occurs at Layer 3. It involves two basic activities: determining optimal routing paths and transporting information groups through an internetwork. Routing protocols use metrics to evaluate what path will be the best for a packet to travel. Routing algorithms initialize and maintain routing tables, which contains route information. Routing algorithms often based on one or more of the design goals like optimality, simplicity, and low overhead, robustness and stability, rapid convergence and flexibility. 2 main types of routing (a.) static and (b.)dynamic and third type of routing is called Hybrid. Static routing involves manually configuring and maintaining route tables by an administrator. Dynamic routing enables routers to "talk" to each other and automatically update their routing tables with the use of broadcasts.

Routing Algorithm Types: Static versus dynamic, single-path versus multipath, flat versus hierarchical, host-intelligent versus router-intelligent, intradomain versus interdomain, link-state versus distance vector. Routing Protocols RIP: Routing Information Protocol is a distance vector dynamic routing protocol and measures the distance from source to destination by counting the number of hops (maximum of 15 hops) that the packets must travel over. OSPF: Open Shortest Path First is a link-state routing protocol. It uses metrics that takes bandwidth and network congestion into making routing decisions and transmits updates only when there is a topology change. It builds a complete topology of the whole network so it requires high processing power, and is suitable if scalability is the main concern. EIGRP: It is Cisco proprietary. Enhanced Interior Gateway Routing Protocol is a hybrid that combines distance vector and link-state technologies. Separate routing tables are maintained for IP, IPX and AppleTalk protocols. Routing update information is forwarded with a single protocol. IGRP: IGRP is Cisco proprietary. Interior Gateway Routing Protocol is a distance vector routing protocol for the interior networks. The metric is a function of bandwidth, reliability, delay, and load. A hold-down timer has a value of 280 seconds is used to prevent routing loops while router tables converge by preventing routers from broadcasting another route to a router which is off-line before all routing tables converge. Exterior Routing Protocols: Use to exchange routing information between autonomous systems and information passed between autonomous systems is called reachability information. Border Gateway Protocol: Based on the OSI InterDomain Routing Protocol and supports policy-based routing.

Numbering Systems Decimal (base 10) numbering: Decimal Number System uses base 10 and includes the digits from 0 through 9. Binary (base 2) Numbering: Works like the decimal number system except the Binary Number System uses base 2 and includes only the digits 0 and 1. Octal Number System: Octal system is based on the binary system with a 3-bit boundary and uses base 8 includes only the digits 0 through 7. Hexadecimal Number System: Uses base 16 and include only the digits 0 through 9 and the letters A, B, C, D, E, and F.

Router Commands TERMINAL CONTROLS: Config# terminal editing: Allows for enhanced editing commands. Config# terminal monitor: Shows output on telnet session. Router Status Introduction Show flash: files in flash Show interfaces: show stats of all the interfaces Show ip route: Displays IP routing table Show access-lists - all access lists on the router Show protocols - routed protocols and net addresses of interfaces Show running-config: dram config file

Show startup-config: nvram config file Show version: ios info, uptime, address of switch Show frame-relay: lmi: lmi stats Show frame-relay map: static and dynamic maps for PVC’s Show frame-relay pvc: pvc’s and dlci’s Show ipx route: ipx routes in the table Show ipx servers: SAP table Show ipx traffic: RIP and SAP info Show isdn active: number with active status Show isdn status: shows if SPIDs are valid, if connected HOST NAME: Config# hostname ROUTER_NAME BANNER: Config# banner motd # TYPE MESSAGE HERE # - # can be substituted for any character, must start and finish the message DESCRIPTIONS: Config# description THIS IS USA ROUTER - can be entered at the Config-if level PPP SETUP: Config-if# encapsulation ppp Config-if# ppp authentication chap pap: order in which they will be used, only attempted with the authentication listed or if one fails, then connection is terminated Config-if# exit Config# username Lab-b password 123456 username is the router that will be connecting to this one Only specified routers can connect. IP ROUTING: Config# ip routing - Enabled by default Config# router rip Config# router igrp 100 Config# interface Ethernet 0 Config-if# ip address 122.2.3.2 255.255.255.0 Config-if# no shutdown IPX ROUTING: Config# ipx routing Config# interface Ethernet 0 Config# ipx maximum-paths 2 - Maximum equal metric paths used Config-if# ipx network 222 encapsulation saps - Also Novell-Ether, SNAP, ARPA on Ethernet. Encapsulation HDLC on serial Config-if# no shutdown IP STANDARD: Config# access-list 10 permit 133.2.2.0 0.0.0.255 - allow all src ip’s on network 133.2.2.0 Config# access-list 10 permit host 133.2.2.2 - specifies a specific host Config# access-list 10 permit any - allows any addressConfig# int Ethernet 0 Config-if# ip access-group 10 in - also available: out IP EXTENDED: Config# access-list 101 permit tcp 133.12.0.0 0.0.255.255 122.3.2.0 0.0.0.255 eq telnet Config# access-list 101 deny tcp any host 133.2.23.3 eq www Config# access-list 101 permit ip any any Config# interface Ethernet 0 Config-if# ip access-group 101 out IPX STANDARD: Config# access-list 801 permit 233 AA3 - source network/host then destination network/host Config# access-list 801 permit -1 -1 - “-1” is the same as “any” with network/host addresses Config# interface Ethernet 0 Config-if# ipx access-group 801 out Copyright Train Signal, Inc., 2002-2005