Router Basics
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Router Basics

Internal Components

  • ROM: Yahan bootstrap program hota hai (PC ke BIOS jaisa).
  • Flash: Isme Cisco IOS stored hota hai (router ka operating system).
  • NVRAM: Permanent storage. Yahan startup-config hoti hai.
  • RAM: Temporary storage. Running-config yahan hoti hai.
  • Processor: Router ka main brain (Motorola, 70 MHz).

Router Startup Process

  1. ROM se bootstrap load hota hai
  2. Bootstrap POST test run karta hai
  3. Flash me IOS dhundta hai
  4. IOS RAM me load hotta hai
  5. NVRAM se startup-config load hotti hai

Router Modes

  • User Mode: Basic commands
  • Privileged Mode: Show commands, troubleshooting
  • Global Config Mode: Router-wide settings
  • Interface Mode: Specific port ki setting
  • ROMMON Mode: Password recovery

Console Connection Steps

  1. Rollover cable → Router
  2. Cable ka second end → PC
  3. Terminal software open karke connect

Basic Commands

User Mode

Router> enable

Privilege Mode (Show Commands)

Router# show running-config
Router# show startup-config
Router# show flash
Router# show version
Router# show ip interface brief

Global Config Mode

Router# configure terminal

Assign IP

Router(config)# interface fa0/0
Router(config-if)# ip address X.X.X.X Y.Y.Y.Y
Router(config-if)# no shut

Set Telnet Password

line vty 0 4
login
password <pass>

Set Console Password

line con 0
login
password <pass>

Set Enable Password

enable secret <password>

Save Configuration

copy running-config startup-config
or
write

Important Show Commands

  • show running-config → RAM config
  • show startup-config → NVRAM config
  • show version → Router info
  • show ip interface brief → Interface status
  • show ip route → Routing table
  • show interfaces → Port details

Basic Rules in Lab

  • Har interface → different network
  • PC & router port → same network
  • Router-to-router ports → same network
  • Same network dobara assign karoge toh error ayega

Example

interface fa0/1
ip address 172.16.0.2 255.255.0.0
no shutdown

Routing

Router dono networks ko learn karta hai → communication possible.

Routing

Routing ka matlab hai network me best path choose karna taaki data fast aur safely destination tak pahunch sake. Router apni routing table check karta hai aur best route choose karta hai.

Types of Routing

1) Static Routing

  • Routes manually add hote hain.
  • Small networks me use hota hai.
  • Fast aur secure.
  • AD value = 1

2) Default Routing

  • Jab router ko destination nahi pata hota, tab packet default route par bheja jata hai.
  • Destination = 0.0.0.0, Mask = 0.0.0.0

3) Dynamic Routing

  • Router automatically route learn karta hai.
  • Large networks me use hota hai.
  • Examples: RIP, OSPF, EIGRP, BGP

IGP vs EGP

  • IGP → Same network/organization ke andar (RIP, OSPF, EIGRP)
  • EGP → Different organizations ke beech (BGP)

Routing Protocol Types

  • Distance Vector → RIP
  • Link State → OSPF
  • Hybrid → EIGRP

Administrative Distance (AD)

Lower AD = more trusted route

  • Connected = 0
  • Static = 1
  • EIGRP = 90
  • OSPF = 110
  • RIP = 120

RIP Simple Points

  • Old, small networks ke liye
  • Metric: Hop count (max 15)
  • Sends updates every 30 seconds
  • RIP v1 = Broadcast
  • RIP v2 = Multicast (224.0.0.9), classless, supports VLSM

EIGRP Simple Points

  • Cisco protocol
  • Fast convergence
  • Metric = Bandwidth + Delay
  • Multicast 224.0.0.10
  • AD = 90

OSPF Simple Points

  • Standard protocol
  • Link-state
  • Metric = Cost
  • Area-based design (must have Area 0)
  • Multicast 224.0.0.5
  • Fast and scalable

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