Farhan Noor Galib (09.01.04.015) Zahidul islam george (09.01.04.023)
What is Router? • A router is a device that acts as a medium for interconnecting several PCs. If a PC named compA wants to send data to compB, the router will choose the best path within the network and send data. • A router is a device that forwards data packets between computer networks
Router is one kind of a ComputerA router is a computer, just like any othercomputer including a PC. The very firstrouter, used for the Advanced ResearchProjects Agency Network (ARPANET),was the Interface Message Processor(IMP). The IMP was a Honeywell 316minicomputer; this computer brought theARPANET to life on August 30, 1969. Interface Message Processor (IMP) – The First Internet Router
Router Classification Non Upgradeable Upgradeable Cannot add and Can add and remove remove the Ethernet interfaces as per or serial interfaces. requirement. Doesn’t have any Number of slots slot. available.
Some other Router types Wireless router It combines a number of base stations (wireless access point) as well as a number of wired LAN switch It connects more than one computer to a single DSL line for Internet access. Modem Routers provides the network Modem router address translation (NAT) which is required to support several computers Brouter A Bridge Router or brouter is a network device that works as a bridge and as a router This router interfaces with an ATM (Asynchronous Transfer Mode) network Edge router Access routers are used in small office/home office (SOHO) networking models. Typically, they are optimized for low Access router costDistribution router Distribution routers aggregate traffic from multiple access routers. . They are often responsible for enforcing quality of service across a WAN A core router may provide a "collapsed backbone" interconnecting the distribution tier routers from multiple buildings Core router of a campus, or large enterprise locations
Some other Router types…(Cont’d)Wireless router Modem router Brouter Edge router Access router Distribution router Core router
Internal Components of a RouterCPU RAM ROM Flash NVRAM NVRAM MemoryCPU executes RAM is volatile ROM does not lose its This is volatile RAM, Non an exampleoperating system memory and it loses its content when the Internetwork similar to Hard Disk. text. Go ahead andinstructions, such as content when the router is powered Operating System replaceknown as Also it with yoursystem initialization, router is restarted. It is down or restarted. A (IOS) developed by permanent storage and own textrouting functions and also known as bootstrap program is Cisco is stored here. is used to load startupswitching functions. temporary storage and located here. It is same IOS is Command line configuration file. is used to store running as the bios of the PC. interface. configuration file.
External Ports (Interfaces) of Router •WAN interfaces 1 •LAN interfaces - Ethernet 2 •Administration 3 interfaces(Configuration) Serial interface (S0, S1 etc) – 60 pin/26 pin(smart serial) ISDN interface(BRI0 etc) – RJ45 WAN WAN interfaces are used to connect routers to external networks, usuallyInterfaces over a larger geographical distance. Similar to LAN interfaces, each WAN interface has its own IP address and subnet mask, which identifies it as a member of a specific network.
Interfaces of router…(Cont’d) AUI (Attachment Unit Interface) (E0)15 pin 10baseT – RJ45 LAN As the name indicates, LAN interfaces are used to connect the router to the LAN, similar to how a PC EthernetInterfaces NIC is used to connect the PC to the Ethernet LAN. Like a PC Ethernet NIC, a router Ethernet interface also has a Layer 2 MAC address and participates in the Ethernet LAN in the same way as any other hosts on that LAN. Console – RJ45 – Local Administration Auxiliary – RJ45 – Remote Administration.Administration The console port is used to connect a terminal, or most often a PC running terminal emulator software, to Interfaces configure the router without the need for network access to that router. The console port must be used during initial configuration of the router. At times the auxiliary port can be used in ways similar to a console port. It can also be used to attach a modem.
Interfaces of router…(Cont’d) Iterfaces along with their Ports
Router acting as FirewallWhy do we need firewall:When our PC is directly connected to the internet, a globally unique IP address isassigned to our PC by the Internet Service Provider (ISP), this address is public i.e. itcan be known to anyone anywhere on the internet. In such cases, anyone can use theIP address of user machine to do some mischievous work.How router act as firewall: What happens in such cases is,the IP address is assigned to the router by ISP (Internet Service Provider) and not to the PC, now it’s the work of router to assign private address to the PC. When we send any packet, router removes the source IP address and attaches its own public IP address, in turn stores the information about all the changes which were made. When any packet comes to the PC , router gets information which it has stored and accordingly routes the packet to the source machine. In this way our PC is not visible on the net, but our PC can see the internet.
Router acting as Firewall…(Cont’d) Lets take a closer look
Router planeA router has two stages of operation called planes: Control Plane Forwarding PlaneControl plane Forwarding plane 1 2 A router records a routing table listing what route The router forwards data packets between should be used to forward a data packet, and incoming and outgoing interface connections. It through which physical interface connection. It routes it to the correct network type using does this using internal pre-configured addresses, information that the packet header contains. It uses called static routes. data recorded in the routing table control plane.
Cisco IOSA router cannot function without an operating system. Without an operating system, the hardware does not have any capabilities.The Cisco Internetwork Operating System (Cisco IOS) is the system software in Cisco devices. Different company uses differentIOS for their devices i.e Juniper uses JUNOS for their devices.The Cisco IOS provides devices with the following network services: Basic routing and switching functions Reliable and secure access to networked resources Network scalabilityThe services provided by the Cisco IOS are generally accessed using a command line interface (CLI). The IOS file itself is severalmegabytes in size and is stored in flash. Flash memory provides non-volatile storage. This means that the contents of the memoryare not lost when the device loses power.
Accessing command line interface(CLI)There are several ways to access the CLI environment. The mostusual methods are: Console Telnet or SSH AUX portConsole:The CLI can be accessed through a console session, also known asthe CTY line. A console uses a low speed serial connection todirectly connect a computer or terminal to the console porton the router or switch. The console port is accessible even if
Accessing CLI….(Cont’d)Telnet and SSH:• A method for remotely accessing a CLI session is to telnet to the router. Unlike the console connection, Telnet sessions require active networking services on the device.• The Secure Shell (SSH) protocol is a more secure method for remote device access. This protocol provides the structure for a remote login similar to Telnet, except that it utilizes more secure network services. SSH provides stronger password authentication than Telnet and uses encryption when transporting session data.AUX port:Another way to establish a CLI sessionremotely is via a telephone dialup connection
Router configuration files 1 The startup configuration file 2 The running configuration file1 The startup configuration file The startup configuration file (startup-config) is used during system startup to configure the device. The startup configuration file is stored in non-volatile RAM (NVRAM). Since NVRAM is non-volatile, when the Cisco device is turned off, the file remains intact. The startup-config files are loaded into RAM each time
Configuration files…(Cont’d)2 The running configuration file Once the startup configuration file is loaded into RAM, it is considered the running configuration or running-config. The running configuration is modified when the network administrator performs device configuration. Because the running configuration file is in RAM, it is lost if the power to the device is turned off or if the device is restarted. Changes made to the running-config file will also be lost if they are not saved to the startup-config file
Router boot-up processStep 1 2 3 4 locating and loading the Performing configurati Loading the Locating and Locating and on file the Power- bootstrap loading Cisco loading the On Self Test program IOS configuration (POST). file
Router boot-up process…(Cont’d) Performing the Power-On Self Test (POST): The Router Performs A POST which is a series of Hardware Test that verify whether all components of the device are functional. Loading the bootstrap program: After the POST process, the router copies the bootstrap program from ROM into RAM. The main purpose of the bootstrap program is to locate the Cisco IOS and load it into RAM.Locating and loading Cisco IOS: The Bootstrap Attempts To Load The IOS From Flash. Usually, the IOS is located in the flash memory, but it can also be stored in a TFTP server If a full IOS image can not be located, a scaled-down version of the IOS is copied from ROM into RAM.
Router boot-up process…(Cont’d) Locating and loading the configuration file:After the IOS is loaded, the bootstrap program searches for the startup configuration file (startup-config) in the NVRAM.If the file exists, it is copied into RAM as the running configuration file (running-config). if the file does not exists, the router may serach for a TFTP server.if the startup configuration file can not be located, the router prompts the user to enter setup mode. setup mode is a series of questions prompting the user for basic configurations information. if the setup mode is not used, the IOS creates a default running-config. this file is a basic configuration file
Router advantages and issuesAdvantages of router: ability to share a network connection with multiple machines, which increases productivity. Routers deliver the packets of data in an organized way, thus lowering the data load. Routers enable a steady and reliable connection between network hosts. Routers make use of alternative parts incase the main parts fail to transfer data packetsRouter issues: Connections can become slow when multiple computers are using a network. This situation is described as "connection lag ". A router basically allows multiple computers to share the same network, which means that the resources of the network are distributed among the machines, and they may run slower as a result.