CCNA RHCE MCITP

INTRODUCTION TO ROUTERS

A router is a device that sends packets from one network to another network. Routers receive packets, read their headers to find addressing information, and send them on to their correct destination on the network or Internet. Routers can forward packets through an internetwork by maintaining routing information in a database called a routing table. The routing table typically contains the address of all known networks and routing information about that network such as:

Interface
Routing Path
Next Hop
Route Metric (Cost)
Route Timeout

Routers build and maintain their routing database by periodically sharing information with other routers. The exact format of these exchanges is based on the routing protocol. The routing protocol
determines:

The information contained in the routing table.
How messages are routed from one network to another
How topology changes (i.e. updates to the routing table) are communicated between routers

Regardless of the method used, changes in routing information take some time to be propagated to all routers on the network. The term convergence is used to describe the condition when all routers have the same (or correct) routing information.

Message Routing Facts

To send a message from one host to another on a different network, the following process is used:
1. The sending host prepares a packet to be sent. It uses its own IP address for the source
Network layer address, and the IP address of the final receiving device as the destination
Network layer address.
2. The sending host creates a frame by adding its own MAC address as the source Physical
layer address. For the destination Physical layer address, it uses the MAC address of the
default gateway router.
3. The sending host transmits the frame.
4. The next hop router reads the destination MAC address in the frame. Because the frame is
addressed to that router, it processes the frame.
5. The router strips off the frame header and examines the packet destination address. It uses a
routing protocol to identify the next hop router in the path.
6. The router repackages the packet into a new frame. It uses its own MAC address as the
source Physical layer address. It uses the MAC address of the next hop router for the
destination Physical layer address.
7. The router transmits the frame.
8. The next hop router repeats steps 4 through 7 as necessary, until the frame arrives at the last
router in the path.
9. The last router in the path receives the frame and checks the destination IP address
contained in the packet.
10. Because the destination device is on a directly connected network, the router creates a frame
using its own MAC address as the source address, and the MAC address of the destination
device as the destination physical address.
11. The router transmits the frame.
12. The destination device receives the frame. Inside the packet it finds the destination address
matching its own IP address, with the source IP address being that of the original sending
device.

Be aware of the following:

On an Ethernet network, the Data Link layer address is the MAC address. On an IP network, the Network layer address is the IP address.

Both Data Link physical addresses and Network logical addresses are used to send packetsbetween hosts.
The Data Link address identifies the physical interface. The Network address contains botha logical network address and a logical device address.
IP (Network layer) addresses are contained in the IP header; MAC (Data Link) addressesare contained in the Ethernet frame header.
Both the source and destination Network and Data Link addresses are typically contained inthe packet.
Data Link addresses in the packet change as the packet is delivered from hop to hop. At anypoint in the process, the Data Link destination address indicates the physical address of the next hop on the route. The Data Link source address is the physical address of the devicesending the frame.
Network addresses remain constant as the packet is delivered from hop to hop. The
Network addresses indicate the logical address of the original sending device and the
address of the final destination device.
A router uses the logical network address specified at the Network layer to forward
messages to the appropriate network segment.

TYPES OF PORTS OF ROUTER

The router contains two different types of ports.They are Interface and Lines

INTERFACES

Interfaces are used to connect the routers with LAN or WAN .Over router we specify the IP addresses .

Some of the Interfaces are

WAN interfaces

1. serial interface(S0,S1 etc)-60pin/26pin(smart serial)

2. ISDN interface(BRI0 etc)-RJ45

LAN interfaces -Ethernet

1. AUI(Attachment Unit Interface)(E0)-15pin

2. 10baseT-RJ45

LINES

Lines are used to get access of a router in order to configur the router.Over line we specify the login and password.Always we used to specify the password first and then we specify the login.Login command activates the line only

The most common examples of lines include:
• Console ports
• Auxiliary ports
• VTY (telnet) ports

Attachment Unit Interface(AUI)

AUI is a 15 pin Ethernet port or LAN port or Default Gateway usedforconnecting LAN to Router.

Sometimes it is known as transceiver which is used for converting 8 wires to 15 wires i.e, RJ45 to 15 pin converter.

Serial port

Serial port is WAN port used for connect either routers directly or remote locations.

V.35 cable is used to connect the serial port locally when two routers are directly connected using a serial cable.

There re two types of serial port

1. 60 pin modular port

2. smart serial port

DB 60 port

It is modular port it is always for 1 terminal.

Smart serial

Latest and compact port used for both 1 terminal and 2 terminal.

Serial cable types

End to end DT/DC cable-60pin or smart serial

One end of serial cable is DTE(Data Terminating Equipment) and Other end odf the serial cable is DCE(Data circuit terminating Equipment)

DCE is always female port.We hae to set the clock rate as 64000.

BRI port

Basic Rate Interface port is port which is used to connect our dedicated ISDN line to our router
It is a RJ-45 female port

Auxiliary port

Ii is used to connect our dedicated telephone to our routers in order to configure it by accessing through this line.
So it is known as Remote Administrative port.
It is RJ-45 female port.
A console or a rollover cable is used to connect to this port.

Console port

It is known as Local Administrative port used for initial configuration,password recovery and local administration of the router.
It is RJ-45 port
It is the most dedicated port of the router.So make less use of the console port

Console Connectivity

Connect a rollover cable to the router console port(RJ-45 connector).
Connect the other end of the rollovercable to the RJ-45 to DB-9 connector
Attach the female DB-9 converter to PC serial port
Open emulation Software on the PC

In Windows

Start-->Programs-->Accessories-->Communications-->Hyper Terminal-->HyperTerminal
Give the Connection Name & select any icon
Select Serial(com) port where router is connected.
In port settings-->click on restore defaults.

In LINUX

#minicom -s

VTY port

Virtual type is a locical part that does not exist physically.
It is used to activate telnet service over the router for the purpose we have to set login and password over vty line.

INTERNAL COMPONENTS OF ROUTER

ROM

POST(Power On Self Test).It is used for hardware testing.
BOOT STRAP:it specify the router from where to load the operating system in router which is similar to BIOS in PC.
It is MINI IOS.

FLASH