Basic Router understanding

What is Router ?

The router is connected to at least two networks and decides which way to send each information packet based on its current understanding of the state of the networks it is connected to. A router is located at any gateway (where one network meets another), including each point-of-presence on the Internet. A router is often included as part of a network switch.

• Series Of Router 800 - 12000
• Types of Router

1.  Fixed Router :-  Fixed Router – we cannot add additional serial port as well as Ethernet port in this Router i.e. 2500 Series  
2. Modular Router – we can add additional Serial port as well as Ethernet port in this Router i.e. 1600, 1700, 2600, 3600, 4500 and above Series

• Operating System of  Router "IOS"  (Internetwork Operating System) 

• IOS version of router (FLASH: ) 

1.  12.0 , 12.1, 12.2 ....
2.  15.0 , 15.1 , 15,2...... 

• Router port :-

           

Aux port :- ( Auxiliary port )

The purpose of the auxiliary port is for connecting to an external modem. Once configured, this modem can be used as a backup demand-dial connection to another location, or as a way to dial in to the router for troubleshooting purposes should regular connectivity fail. Unlike the console port, the auxiliary port supports hardware flow control, which ensures that the receiving device receives all data before the sending device transmits more. In cases where the receiving device’s buffers become full, it can pass a message to the sender asking it to temporarily suspend transmission. This makes the auxiliary port capable of handling the higher transmission speeds of a modem.

console port :-Users using the console port to access the router are automatically directed to the IOS command-line interface, 

in the diagram we can see how to connect console port 

1 we have console cable ( roll over cable ) 

2 connect RJ45 on console port and serial port on pc serial interface 

3 then goto hyper terminal or putty software and click on serial and set the com port number

4 then click ok if port is ok connection will be appear 

5 Now we can see CLI of  Router 

   

let's see..

1)  After downloading PuTTY, connect the console cable with Cisco Router or Swtich, double click putty.exe to execute it. Expand Connection > Serial. Enter the port number inside "Serial line to connect to" text box. The port number is COM1 (select as your PC given ) in below example. The port number may be different in your computer. Enter the correct port number when you connect from your computer. Enter other values also as shown below.

• Bits per sec: 9600

• Data bits: 8

• Parity: none

• Stop bits: 1

• Flow control: none

then click OPEN 

Here Router CLI mode and Start the configuration 

Configuring Ethernet, Fast Ethernet, or Gigabit Ethernet Interfaces

 Cisco supports 10-Mbps Ethernet,

100-Mbps Fast Ethernet,

1000-Mbps Gigabit Ethernet.

Support for the 10-Mbps, 100-Mbps, and 1000-Mbps Ethernet interface is supplied on various Ethernet network interface cards or systems. 

Cisco 7200 Series Routers with FastEthernet and Gigabit Ethernet

Cisco 7200 series routers support an I/O controller with an RJ-45 interface for Fast Ethernet support and an I/O controller with both RJ-45 and GBIC interfaces for Gigabit Ethernet support. 

Serial port :- 

Serial port connection are use to connect to or more router via serial interface to transfer packet

Before you connect a device to a serial port, you need to know the following:

•      Type of device—data terminal equipment (DTE) or data communications equipment
       (DCE)—you are     connecting to

•     Type of connector, male or female, needed to connect to the device

•     Signaling standard required by the device 

About DTE and DCE Devices

A device that communicates over a synchronous serial interface is either a DTE or a DCE device. A DCE device provides a clock signal between the device and the router. A DTE device does not provide a clock signal. DTE devices usually connect to DCE devices. The documentation that accompanied the device should tell you whether it is DTE or DCE. (Some devices have a jumper to select DTE or DCE mode.) If you cannot find this information in your documentation, see Table 1 to help you determine the proper device type.

Table 1 Identifying the Device Type

Device Type	Typical Connector	Typical Devices
DTE	Male1	Terminal PC
DCE	Female2	Modem CSU/DSU Multiplexer

more about serial in details....

visit http://www.cisco.com/c/en/us/td/docs/routers/access/interfaces/nm/hardware/installation/guide/ConntSer.html#wp1022382 

Router internal :- 

CPU – The Central Processing Unit (CPU) executes instructions in the operating system. Among these functions are system initialization, routing functions, and network interface control. The CPU is a microprocessor. Large routers may have multiple CPUs.  RAM – Random-access memory (RAM) is used for routing table information, fast switching cache, running configuration, and packet queues. In most routers the RAM provides run time space for executable Cisco IOS software and its subsystems. RAM is usually logically divided into main processor memory and shared input/output (I/O) memory. Shared I/O memory is shared among interfaces for temporary storage of packets. The contents of RAM are lost when power is removed. RAM is generally dynamic random-access memory (DRAM) and can be upgraded by adding additional Dual In-Line Memory Modules (DIMMs).  Flash – Flash memory is used for storage of a full Cisco IOS software image. The router normally acquires the default IOS from flash. These images can be upgraded by loading a new image into flash. The IOS may be in uncompressed or compressed form. In most routers an executable copy of the IOS is transferred to RAM during the boot process. In other routers the IOS may be run directly from flash. Adding or replacing the flash Single In-Line Memory Modules (SIMMs) or PCMCIA cards can upgrade the amount of flash.  NVRAM – Nonvolatile random-access memory (NVRAM) is used to store the startup configuration. In some devices, NVRAM is implemented using separate electronically erasable programmable read-only memory (EEPROMs) in some devices. In other devices it is implemented in the same flash device from which the boot code is loaded. In either case these devices retain contents when power is removed. Buses – Most routers contain a system bus and a CPU bus. The system bus is used for communication between the CPU and the interfaces and/or expansion slots. This bus transfers the packets to and from the interfaces. The CPU bus is used by the CPU for accessing components from router storage. This bus transfers instructions and data to or from specified memory addresses.    ROM – Read-only memory (ROM) is used for permanently storing startup diagnostic code (ROM Monitor). The main tasks for ROM are hardware diagnostics during router bootup and loading the Cisco IOS software from flash to RAM. Some routers also have a scaled down version of the IOS that can be used as an alternative boot source. ROMs are not erasable. They can only be upgraded by replacing the ROM chips in the sockets.  Interfaces – The interfaces are the router connections to the outside. The three types of interfaces are local-area network (LANs), wide-area network (WANs), and Console/AUX. The LAN interfaces are usually one of several different varieties of Ethernet or Token Ring. These interfaces have controller chips that provide the logic for connecting the system to the media. The LAN interfaces may be a fixed configuration or modular. The WAN interfaces include serial, ISDN, and integrated Channel Service Unit (CSUs). As with LAN interfaces, WAN interfaces also have special controller chips for the interfaces. The WAN interfaces may be a fixed configuration or modular. The Console/AUX ports are serial ports used primarily for the initial configuration of the router. These ports are not networking ports. They are used for terminal sessions from the communication ports on the computer or through a modem.  Power Supply – The power supply provides the necessary power to operate the internal components. Larger routers may use multiple or modular power supplies. In some of the smaller routers the power supply may be external to the router.

 

 

 

 

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