CCNA 200-301

CCNA – Cisco Certified Network Associate 200-301

Cisco Systems in 2026 is a global leader in networking, AI infrastructure, and cyber security, headquartered in San Jose, California, with about 86,000 employees and annual revenues exceeding $51 billion. It remains one of the world’s largest technology companies,

 CCNA – Cisco Certified Network Associate

• Purpose: Entry-level certification for networking professionals.

• Focus: Builds foundational knowledge of networking, IP connectivity, security fundamentals, automation, and cloud basics.

• Who it’s for: Beginners starting a career in networking or IT support.

• Goal: To validate that you can install, configure, and troubleshoot small to medium-sized networks.

CCNP – Cisco Certified Network Professional

• Purpose: Mid-level certification for advanced networking skills.

• Focus: Enterprise networking, routing, switching, security, automation, and collaboration.

• Who it’s for: Professionals with experience who want to specialize in areas like security, data center, or collaboration.

• Goal: To prove you can design, implement, and manage complex enterprise networks.

 CCIE – Cisco Certified Internetwork Expert

• Purpose: Expert-level certification, one of the most prestigious in networking.

• Focus: Advanced design, troubleshooting, and optimization of large-scale, complex networks.

• Who it’s for: Senior engineers, architects, and consultants aiming for top-tier expertise.

• Goal: To demonstrate mastery in planning, operating, and troubleshooting enterprise-grade networks with automation and AI-driven tools.

The CCNA (Cisco Certified Network Associate) certification opens doors to a wide range of entry-level and mid-level IT jobs because it proves you understand networking fundamentals, security basics, and automation.

Jobs You Can Achieve with CCNA

1. Network Support Engineer

• Troubleshoot LAN/WAN issues, configure routers/switches.

• First step into networking careers.

2. System/Network Administrator

• Manage servers, Active Directory, and enterprise networks.

• CCNA validates your ability to maintain stable IT infrastructure.

3. Technical Support Engineer

• Provide IT support for hardware, software, and connectivity.

• CCNA helps you solve network-related problems quickly.

4. Helpdesk Engineer

• Entry-level role assisting users with connectivity and system issues.

• CCNA knowledge makes you stand out from other support staff.

5. Cybersecurity Analyst (Junior)

• Monitor network traffic, detect threats, and apply security policies.

• CCNA’s security fundamentals are a strong foundation.

6. Field Engineer / Network Technician

• Install and maintain networking equipment at client sites.

• CCNA ensures you can handle real-world networking tasks.

7. Cloud Support Associate

• Assist in hybrid cloud environments (Azure, AWS, Cisco Meraki).

• CCNA now includes cloud and automation basics.

 

CCNA 200‑301 Exam (2026)

• Format: Single exam, ~120 questions.

• Location: Pearson VUE certification centers (online or offline).

• Purpose: Entry-level networking certification covering fundamentals, security, automation, and cloud readiness.

Note:

Pearson VUE (Virtual University Enterprises) is a global testing organization.

It provides secure, computer-based exams for IT certifications (like Cisco CCNA/CCNP/CCIE), academic tests, and professional licenses.

Operates worldwide testing centers and also supports online proctored exams.

Ensures identity verification, exam security, and standardized delivery.

 Updated Curriculum Modules (2026)

1. Network Fundamentals

• Routers, switches, cabling

• TCP/UDP basics

• IPv4 & IPv6 addressing

2. IP Connectivity

• IP routing concepts

• OSPFv2 configuration & troubleshooting

3. IP Services

• NTP (time sync)

• DHCP (IP assignment)

• QoS (Quality of Service)

• SNMP (network monitoring)

4. Security Fundamentals

• VPNs (secure remote access)

• Wireless security (WPA2/3)

• Port security

5. Network Access

• VLANs & trunking

• EtherChannel (link aggregation)

6. Automation & Programmability

• REST APIs

• Puppet, Chef (automation tools)

• JSON data formats

• SDN (Software Defined Networking)

Switch:- A switch is a networking device that connects multiple devices in a local area network (LAN) and forwards data only to the specific device it is meant for, based on its MAC address. In simple terms, it acts like a smart traffic controller inside a network, ensuring that data goes directly to the right destination instead of broadcasting everywhere.

1. Unmanaged Switch

• Definition: A plug‑and‑play device with no configuration options. It simply connects devices in a LAN.

• Use: Small offices or labs where simplicity is enough.

• Cisco Model Example: Cisco Small Business 110 Series (e.g., SF110D-08).

2. Managed Switch

• Definition: A configurable switch that allows administrators to monitor, control, and optimize traffic (VLANs, QoS, SNMP, security).

• Use: Enterprise networks needing performance tuning and security.

• Cisco Model Example: Cisco Catalyst 2960-X Series (e.g., WS-C2960X-24TS-L).

3. Layer 2 Switch

• Definition: Operates at the Data Link Layer, forwarding frames based on MAC addresses.

• Use: LAN environments where routing is handled by a router.

• Cisco Model Example: Cisco Catalyst 2960-L Series (e.g., WS-C2960L-24TQ-LL).

4. Layer 3 Switch

• Definition: Works at both Data Link and Network Layers, capable of routing between VLANs and subnets using IP addresses.

• Use: Large networks requiring internal routing and segmentation.

• Cisco Model Example: Cisco Catalyst 3850 Series (e.g., WS-C3850-24T-S).

5. PoE (Power over Ethernet) Switch

• Definition: Provides both data and electrical power through Ethernet cables to devices like IP phones, cameras, and access points.

• Use: Offices with VoIP phones, CCTV, or Wi-Fi access points.

• Cisco Model Example: Cisco Catalyst 9300 PoE Switch (e.g., C9300-24P-E).

6. Stackable Switch

• Definition: Multiple switches can be interconnected and managed as one unit.

• Use: Scalable enterprise networks needing redundancy and easy expansion.

• Cisco Model Example: Cisco Catalyst 9300 Stack (e.g., C9300-48T-E with StackWise cables).

7. Modular Switch

• Definition: Customizable with slots for adding modules (fiber, copper, or extra ports).

• Use: Data centers and backbone networks needing flexibility.

• Cisco Model Example: Cisco Catalyst 9400 Series (e.g., C9407R chassis).

8. Fixed‑Configuration Switch

• Definition: Comes with a set number of ports and features; cannot be expanded.

• Use: Standard LAN setups with predictable device counts.

• Cisco Model Example: Cisco Catalyst 2960-X (24 or 48 ports).

9. Virtual Switch

• Definition: A software‑based switch used in virtualized environments to connect virtual machines.

• Use: Cloud computing and virtualization labs.

• Cisco Model Example: Cisco Nexus 1000V Virtual Switch (for VMware/Hyper-V).

1. Core Layer – Cisco Catalyst 9400 (Modular Backbone)

Definition:

The Core Layer is the backbone of the network. It provides high‑speed, reliable data transport between different parts of the network. It focuses on performance, redundancy, and fast switching, not policy enforcement.

Function:

• Connects multiple distribution layers.

• Handles large volumes of traffic quickly.

• Provides fault tolerance and redundancy.

• Uses high‑capacity Layer 3 switches for routing.

Cisco Example:

Cisco Catalyst 9400 Series (e.g., C9407R, C9410R) — modular chassis switch supporting advanced routing protocols (OSPF, EIGRP, BGP) and high throughput.

Real‑World Example:

In a university network, the 9400 connects different buildings (engineering, library, admin) and routes data between them at high speed.

2. Distribution Layer – Cisco Catalyst 3850 (Layer 3 Switch)

Definition:

The Distribution Layer acts as a bridge between the core and access layers. It controls network policies, routing between VLANs, and traffic management.

Function:

• Performs inter‑VLAN routing.

• Implements security policies and access control lists (ACLs).

• Aggregates traffic from access switches before sending it to the core.

• Provides load balancing and redundancy.

Cisco Example:

Cisco Catalyst 3850 Series (e.g., WS‑C3850‑24T‑S) — supports Layer 3 routing, QoS, and stacking for scalability.

Real‑World Example:

In an office network, the 3850 connects multiple floors’ access switches and routes traffic between VLANs (e.g., HR, Accounts, IT).

3. Access Layer – Cisco Catalyst 2960‑X (Layer 2 Switch)

Definition:

The Access Layer is where end‑user devices (PCs, printers, IP phones) connect to the network. It focuses on device connectivity and port security.

Function:

• Provides network access to users.

• Handles MAC address learning and frame forwarding.

• Supports VLAN segmentation.

• Implements port security and PoE for end devices.

Cisco Example:

Cisco Catalyst 2960‑X Series (e.g., WS‑C2960X‑24TS‑L) — Layer 2 switch with Gigabit ports, VLAN support, and PoE options.

Real‑World Example:

In a computer lab, the 2960‑X connects all student PCs and printers to the network, forwarding traffic to the 3850 for routing.

Working of a Switch

1. MAC Address Learning

• When a device (like a PC or printer) sends data, the switch reads the source MAC address and records it in its MAC address table along with the port number.

• Example: If PC A is connected to port 1, the switch stores Port 1 → MAC: AA:BB:CC:11:22:33.

2. Frame Forwarding

• When the switch receives a frame, it looks at the destination MAC address.

• If the MAC is in its table, the switch forwards the frame only to the correct port (instead of broadcasting everywhere).

• Example: If Laptop B wants to send data to PC A, the switch checks the table and forwards only to PC A’s port.

3. Collision Avoidance

• Unlike hubs, switches create a separate collision domain per port.

• This means each device has its own dedicated bandwidth, preventing data collisions.

• Example: PC A and Camera D can send data at the same time without interfering.

4. Efficient Data Delivery

• Switches ensure that data reaches the intended device only, improving speed and security.

• Example: If Camera D sends video data, only the monitoring PC receives it — not every device in the network.

What is PuTTY?

• PuTTY is a free, open‑source terminal emulator.

• It allows you to connect to network devices (like Cisco switches, routers, servers) using protocols such as:

  • SSH (Secure Shell)

  • Telnet

  • Serial (COM port)

  • Rlogin

It’s widely used by network engineers and system administrators to configure and manage devices.

How PuTTY is Used in Networking

1. Connect to Cisco Switch/Router:

   • Plug in a console cable (RJ‑45 to USB/COM).

   • Open PuTTY → choose Serial → set COM port (e.g., COM3).

   • Configure baud rate (usually 9600 for Cisco devices).

   • Click Open → CLI of the switch/router appears.

2. Remote Access via SSH/Telnet:

   • Enter the IP address of the device.

   • Select SSH (preferred) or Telnet.

   • Login with username and password.

3. Configuration Tasks:

   • Run Cisco IOS commands.

   • Save configurations.

   • Troubleshoot connectivity.

Real‑World Example

In your NSN COMPUTER lab:

• Students use PuTTY to connect to Cisco Catalyst switches (2960‑X, 3850).

• They practice basic configuration (hostname, VLANs, IP address).

• acts as the bridge between their PC and the switch/router CLI.

PuTTY Alternatives Explained

1. Tera Term

• Free, open‑source terminal emulator.

• Supports SSH, Telnet, Serial connections.

• Simple interface, lightweight, and widely used in labs.

• Best for basic console access to Cisco devices.

2. SecureCRT

• Commercial (paid) software by VanDyke.

• Advanced features: tabbed sessions, scripting, secure file transfer.

• Strong encryption and enterprise‑grade security.

• Best for professional environments where multiple secure sessions are needed.

3. KiTTY

• A modified version of PuTTY with extra features.

• Adds session filters, automatic login, portability, and scripting.

• Looks and feels like PuTTY but more powerful.

• Best for users who want PuTTY with added productivity tools.

4. MobaXterm

• All‑in‑one terminal for Windows.

• Supports SSH, X11, RDP, VNC, FTP, SFTP in one application.

• Includes a built‑in X server for graphical Linux apps.

• Best for admins who need multiple protocols in one tool.

5. HyperTerminal

• Legacy Windows terminal emulator (older versions of Windows).

• Supports serial connections (COM ports).

• Very basic, no longer updated.

• Best for legacy labs or old hardware.

6. OpenSSH (Linux/Mac built‑in)

• Command‑line SSH client included in Linux and macOS.

• Secure, fast, and widely used.

• Best for direct remote access from Linux/Mac terminals.

7. ZOC Terminal

• Paid professional terminal emulator.

• Supports SSH, Telnet, Rlogin, Serial, scripting, tabbed sessions.

• Highly customizable with automation features.

• Best for advanced users needing automation and multiple connections.

Cisco Switch Modes

1. User EXEC Mode

• Prompt: Switch>

• Limited commands (basic monitoring, no configuration).

• Default entry mode when you connect via console, SSH, or Telnet.

2. Privileged EXEC Mode (Enable Mode)

• Prompt: Switch#

• Full access to show commands and configuration.

• Entered by typing:

• Switch> enable

• Without security, anyone can access this mode, so passwords are essential.

3. Global Configuration Mode

• Prompt: Switch(config)#

• Accessed from Enable mode with:

• Switch# configure terminal

• Used for making permanent configuration changes.

Securing Enable Mode Login

You can secure access by setting passwords:

• Enable Password (basic, less secure):

  Switch(config)# enable password mypassword

• Enable Secret (recommended, encrypted):

  • Stored in encrypted form in the configuration.

  • Overrides enable password if both are set.

• Switch(config)# enable secret mysecret

• 
  

• Username/Password with Privilege Level:

  Switch(config)# username admin privilege 15 secret strongpass

  Switch(config)# line vty 0 4
  Switch(config-line)# login local
  

• Ensures remote logins (Telnet/SSH) require credentials.

• Privilege level 15 = full access (Enable mode).

A VLAN (Virtual Local Area Network) is a logical segmentation of a physical network that divides one switch into multiple isolated broadcast domains, improving security, performance, and manageability. In simple terms, it allows you to group devices together logically, even if they’re not physically connected to the same switch port.

Key Concepts of VLAN

• Definition: VLAN = Virtual Local Area Network. It’s a way to create multiple logical networks on a single physical switch.

• Layer: Operates at Layer 2 (Data Link Layer) of the OSI model.

• Implementation: Uses IEEE 802.1Q tagging to mark frames with VLAN IDs.

• Broadcast Control: Each VLAN is its own broadcast domain, meaning broadcast traffic stays within that VLAN only.

VLAN Range (IEEE 802.1Q Standard)

• Normal Range: 1 – 1005

  • Commonly used VLANs.

  • VLAN 1 is the default VLAN (cannot be deleted).

  • VLANs 1002–1005 are reserved for legacy technologies (like FDDI and Token Ring).

• Extended Range: 1006 – 4094

• Available on switches that support VTP transparent mode or VTP version 3.

• Useful for large enterprise networks needing more VLANs.

Major Benefits of VLANs

1. Reduced Broadcast Traffic VLANs limit broadcast domains, preventing unnecessary traffic from reaching all devices and reducing CPU overhead on network devices.

2. Improved Security By isolating groups of devices, VLANs prevent unauthorized access between departments or user groups, adding an extra layer of protection.

3. Better Network Performance Segmentation reduces congestion and improves overall speed and efficiency of the network.

4. Logical Grouping of Devices Devices can be grouped by function (e.g., HR, Finance, Students) instead of physical location, making management more flexible.

5. Simplified Management VLANs make it easier to manage devices, apply policies, and troubleshoot issues since groups are logically defined.

6. Enhanced Flexibility Users can be moved across physical locations without changing their network configuration, as VLAN membership is logical.

7. Cost Efficiency VLANs reduce the need for expensive hardware like routers to separate broadcast domains, since segmentation is handled at the switch level.

• 
  

Spanning Tree Protocol (STP)

Spanning Tree Protocol (STP) is a Layer 2 network protocol designed to prevent loops in a network topology. It ensures that even if there are redundant paths between switches in a LAN, only one active path is used at a time, while others remain in standby mode.

• Purpose: Prevents broadcast storms, MAC table instability, and multiple frame copies caused by loops.

• Standard: Defined in IEEE 802.1D.

• Process: Uses BPDU (Bridge Protocol Data Units) to share information between switches.

• Root Bridge: STP elects one switch as the Root Bridge (lowest Bridge ID).

• Port Roles:

  • Root Port (RP): Best path to the Root Bridge.

  • Designated Port (DP): Forwards traffic for a segment.

  • Blocked Port (BP): Disabled to prevent loops.

• Port States: Blocking → Listening → Learning → Forwarding

Port State	Function	Default Time
Blocking	Port does not forward frames; only listens to BPDUs. Prevents loops.	~20 seconds (Max Age timer)
Listening	Port listens to BPDUs, decides role (Root/Designated/Blocked). No frame forwarding.	15 seconds (Forward Delay)
Learning	Port learns MAC addresses, updates table. Still not forwarding frames.	15 seconds (Forward Delay)
Forwarding	Port forwards frames and learns MAC addresses. Fully operational.	Continuous (until topology change)
Disabled	Port administratively shut down; not part of STP.	N/A

• STP compares all Bridge IDs in the network.

• The switch with the lowest Bridge ID becomes the Root Bridge.

• If all switches have the same priority, the one with the lowest MAC address is chosen.

Cisco Password Types (Notes)

1. Console Password

Secures access through the console port when connecting directly with a cable.

2. Telnet / VTY Password

Protects remote login sessions (Telnet/SSH) to the device.

3. Auxiliary (AUX) Password

Secures access through the AUX port, often used for modem or backup connections.

4. Enable Password

Allows entry into Privileged EXEC mode, but stored in plain text (less secure).

5. Enable Secret Password

Also allows entry into Privileged EXEC mode, but stored in encrypted form (more secure).

1. Console Password

• Secures access through the console port (local physical connection).

• Command:

  Code

  Switch(config)# line console 0
  Switch(config-line)# password nsnconsole
  Switch(config-line)# login
  

2. Telnet / VTY Password

• Secures remote login via Telnet or SSH.

• Command:

  Code

  Switch(config)# line vty 0 4
  Switch(config-line)# password nsnremote
  Switch(config-line)# login
  

3. Auxiliary (AUX) Password

• Secures access through the AUX port (used for modem or backup).

• Command:

  Code

  Router(config)# line aux 0
  Router(config-line)# password nsnaux
  Router(config-line)# login
  

4. Enable Password

• Protects Privileged EXEC mode (Switch#).

• Stored in plain text (less secure).

• Command:

  Code

  Switch(config)# enable password nsn123
  

5. Enable Secret Password

• Also protects Privileged EXEC mode.

• Stored in encrypted form (more secure).

• Always preferred over enable password.

• Command:

  Switch(config)# enable secret nsnsecure
  
  
  
  6.SSH

• 
  

Router

Cisco IOS (Internetwork Operating System) is the proprietary software that runs on Cisco routers and switches, providing the essential functions for routing, switching, internetworking, and device management through a command-line interface (CLI). It acts as the operating system that controls the hardware and enables administrators to configure, secure, and monitor network devices.

Functions of IOS

• Controls hardware: Manages router interfaces and modules.

• Protocol support: Runs IP, IPv6, and legacy protocols like IPX (Internetwork Packet Exchange).

• Traffic management: Decides best paths for data packets.

• Security enforcement: Prevents unauthorized access and ensures secure communication.

• Network stability: Keeps connections reliable and efficient.

Examples of Cisco IOS Versions

• IOS 12.x → Widely used in enterprise routers, introduced modular features.

• IOS 15.x → Common in modern routers, supports IPv6, advanced security, and QoS.

• IOS XE → A newer, modular version built on Linux, used in high-performance routers (e.g., Cisco ASR series).

• IOS XR → Designed for carrier-grade routers, highly scalable, used in service provider networks.

• Catalyst IOS → Specialized IOS for Cisco Catalyst switches.

Types of Routers in Networking

1. Wired Routers

• Connect devices via Ethernet cables.

• Provide stable, high-speed connections.

• Common in offices where reliability is critical.

2. Wireless Routers

• Use Wi-Fi signals to connect multiple devices without cables.

• Most common in homes and small businesses.

• Example: Standard Wi-Fi routers bundled with broadband connections.

3. Edge Routers

• Positioned at the boundary of a network.

• Connect internal networks to external networks (e.g., LAN to ISP).

• Handle traffic entering or leaving the network.

4. Core Routers

• Found in the backbone of large networks.

• Provide high-speed, high-capacity routing within the network.

• Used by ISPs and large enterprises.

5. SOHO Routers (Small Office/Home Office)

• Designed for small-scale networks.

• Combine routing, firewall, and wireless access in one device.

• Affordable and easy to configure.

6. Virtual Routers

• Software-based routers running on virtual machines.

• Useful in cloud computing and virtualized environments.

• Example: Cisco CSR1000v (Cloud Services Router).

7. Broadband Routers

• Used with DSL, cable, or fiber connections.

• Often include built-in modems.

• Provide Internet access for homes and small offices.

Types of Routers CCNA

1. Edge Routers

• Definition: Routers placed at the boundary of a network, connecting internal LANs to external WANs or the Internet.

• Function: Handle traffic entering or leaving the enterprise network.

• Use Case: Enterprises use edge routers to connect their LAN to an ISP.

• Example: Cisco ASR 1000 Series.

• Key Point: Acts as the “gateway” between private and public networks.

2. Branch Routers

• Definition: Routers deployed in branch offices or remote sites.

• Function: Provide secure connectivity between branch offices and headquarters.

• Use Case: A company with multiple offices uses branch routers to connect remote sites to the main data center.

• Example: Cisco ISR 4000 Series.

• Key Point: Optimized for WAN connectivity, VPNs, and secure remote access.

3. Service Provider / ISP Routers

• Definition: High-capacity routers used by Internet Service Providers (ISPs).

• Function: Route massive amounts of data across the Internet backbone.

• Use Case: Telecom companies and ISPs use these to manage customer connections and global traffic.

• Example: Cisco CRS Carrier Routing System 322 tb

• Series, Cisco NCS Network Convergence System 1pb

• Series.

• Key Point: Designed for scalability, reliability, and carrier-grade performance.

Types of Ports in a Cisco Router

1. Console Port

• Purpose: Used for local configuration and management of the router.

• Connection: Requires a console cable (RJ-45 to DB-9 or USB).

• Use Case: Initial setup, troubleshooting, password recovery.

• Key Point: Provides direct access to the router’s CLI, bypassing the network.

2. Auxiliary (AUX) Port

• Purpose: Provides remote management using a modem connection.

• Connection: Serial/modem cable.

• Use Case: Backup access when console or network access is unavailable.

• Key Point: Rarely used today, but important in legacy setups.

3. Ethernet Ports (LAN/WAN Interfaces)

• Purpose: Connect the router to LANs and WANs.

• Types:

  • Fast Ethernet (FE) → 100 Mbps

  • Gigabit Ethernet (GE) → 1 Gbps

  • 10 Gigabit Ethernet (10GE) → 10 Gbps

• Use Case: Connecting to switches, other routers, or ISP links.

• Key Point: Main data-carrying interfaces for routing traffic.

4. WAN Interface Ports

• Purpose: Connect to Wide Area Networks (ISP, MPLS, leased lines).

• Types:

  • Serial interfaces

  • DSL, cable, or fiber interfaces (modern routers) Digital Subscriber Line.

• Use Case: Enterprise WAN connectivity.

• Key Point: Provide external network access beyond the LAN.

5. USB Ports

• Purpose: Used for storage, software upgrades, or console access.

• Use Case: Loading IOS images, saving configurations, or connecting USB console cables.

• Key Point: Modern routers often include USB for convenience.

• Console Port allows direct local setup and troubleshooting.

• Auxiliary Port provides remote access via modem.

• Ethernet Ports connect LANs and WANs for data transfer.

• WAN Interfaces link routers to external networks or ISPs.

• USB Ports help in software upgrades and configuration storage.

• Management Port enables secure, out-of-band device management.

Cisco routers use four main types of memory — RAM, ROM, NVRAM, and Flash — each serving a distinct role in storing configurations, operating systems, and boot instructions.

Types of Memory in a Cisco Router

1. RAM (Random Access Memory)

• Function: Temporary working memory used while the router is running.

• Stores:

  • Running configuration (current settings in use).

  • Routing tables and ARP cache.

  • Packet buffers for data being processed.

• Volatile: Contents are erased when the router is powered off or restarted

Router# show running-config

2. NVRAM (Non-Volatile RAM)

• Function: Stores the startup configuration file.

• Non-volatile: Data remains even after power loss.

• Use Case: When the router boots, it loads configuration from NVRAM into RAM.

• Example Command:

Router# show startup-config

3. ROM (Read-Only Memory)

• Function: Contains bootstrap program and POST (Power-On Self-Test) instructions.

• Purpose:

  • Initializes hardware.

  • Loads the Cisco IOS from Flash into RAM.

  • Provides a mini IOS (RxBoot) for recovery if Flash is corrupted.

• Non-volatile: Retains content permanently.

• Key Point: Essential for router startup and diagnostics.

4. Flash Memory

• Function: Stores the Cisco IOS image and other system files.

• Non-volatile: Retains data even when powered off.

• Upgradable: Can be erased and rewritten to install new IOS versions.

• Example Command:

Router# show flash

Definition of Routing

• Routing is the method of forwarding data packets from one network to another based on their destination IP address.

• It occurs at the Network Layer (Layer 3) of the OSI model.

• Routers are the devices that perform routing, acting like “traffic controllers” for data.

How Routing Works

1. Packet Creation → Data is broken into packets, each tagged with a destination IP.

2. Router Receives Packet → Reads the destination IP address in the header.

3. Routing Table Lookup → Router checks its routing table to find the best path.

4. Forwarding Decision → Packet is sent to the next hop (another router or destination).

5. Delivery → Process repeats until the packet reaches its destination.

Types of Routing

1. Static Routing

• Routes are manually configured by the administrator.

• Simple but not scalable.

• Best for small networks.

2. Dynamic Routing

• Routers automatically adjust routes using routing protocols (RIP, OSPF, EIGRP, BGP).

• Adapts to network changes like failures or congestion.

• Best for large, complex networks.

3. Default Routing

• Packets with no specific route are sent to a default gateway.

• Common in networks with a single exit point (e.g., home or small office).

4. Directly Connected Routing

• Routes are created automatically when a router interface is assigned an IP address and is up/up (active).

• No manual configuration or protocol needed.

• Best for simple connections between directly attached networks.

• Example: If Router A has an IP on 192.168.1.1/24, it automatically knows how to reach 192.168.1.0/24 without extra configuration.

ROUTER-2

ip configuration

R1>enable

R1#configure terminal

R1(config)#interface fastEthernet 0/0

R1(config-if)#ip address 192.168.1.5 255.255.255.0

R1(config-if)#no shutdown

DHCP CONFIGRATION

R1>enable

R1#configure terminal

R1(config)#ip dhcp pool tj

R1(dhcp-config)#default-router 192.168.1.5

R1(dhcp-config)#network 192.168.1.0 255.255.255.0

ROUTER-2

R2>enable

R2#configure terminal

R2(config)#interface fastEthernet 0/0

R2(config-if)#ip address 192.168.2.18 255.255.255.0

R2(config-if)#no shutdown

R2(config-if)#exit

R2(config)#ip dhcp pool tj

R2(dhcp-config)#ip dhcp pool tj1

R2(dhcp-config)#default-router 192.168.2.18

R2(dhcp-config)#network 192.168.2.0 255.255.255.0

R1>enable

R1#configure terminal

R1(config)#interface fastEthernet 0/1

R1(config-if)#ip address 193.168.3.1 255.255.255.0

R1(config-if)#no shutdown

R2>enable

R2#conf t

R2(config)#int fa0/1

R2(config-if)#ip address 193.168.3.2 255.255.255.0

R2(config-if)#no shutdown

Static Routing

ip route <destination-network> <subnet-mask> <next-hop-address or exit-interface>

Explanation of Parameters

• destination-network → The network you want to reach (e.g., 192.168.1.0).

• subnet-mask → The subnet mask of the destination network (e.g., 255.255.255.0).

• next-hop-address → The IP address of the next router to forward packets to.

• exit-interface → The local interface through which packets should be sent.

R1>enable

R1#configure terminal

R1(config)#ip route 192.168.2.0 255.255.255.0 193.168.3.2

R2>enable

R2#conf t

R2(config)#ip route 192.168.1.0 255.255.255.0 193.168.3.1

Dynamic Routing

Dynamic Routing is a method where routers automatically learn and update routes to reach different networks using routing protocols — instead of manually configuring routes.

How It Works

1. Routers exchange information using routing protocols (like RIP, OSPF, EIGRP, BGP).

2. Each router builds a routing table based on received updates.

3. If a network changes (link fails or new route appears), routers automatically adjust — no manual setup needed.

	Type	Algorithm	Description
RIP (Routing Information Protocol)	Distance Vector	Bellman-Ford Algorithm	Uses hop count as metric; updates every 30 seconds.
OSPF (Open Shortest Path First)	Link State	Dijkstra’s Algorithm (Shortest Path First)	Calculates best path based on cost (bandwidth).
EIGRP (Enhanced Interior Gateway Routing Protocol)	Hybrid	DUAL (Diffusing Update Algorithm)	Combines distance vector + link state; fast convergence.
IS-IS (Intermediate System to Intermediate System	Link State	Dijkstra’s Algorithm	Similar to OSPF; used in large enterprise networks.

IGP (Interior Gateway Protocol)

IGP is a type of routing protocol used within a single Autonomous System (AS), meaning it helps routers inside one organization or network communicate and find the best path for data. Example: OSPF is an IGP that uses the Dijkstra algorithm to calculate the shortest path inside a company’s network.

EGP (Exterior Gateway Protocol) EGP is a routing protocol used between different Autonomous Systems, meaning it helps large networks (like ISPs or enterprises) exchange routing information with each other. Example: BGP is the only widely used EGP today, and it ensures data can travel across the Internet between multiple organizations.

• Distance Vector Routing Protocol A routing protocol where each router calculates the best path to a destination based only on information from its neighboring routers.

  • Uses the Bellman-Ford algorithm.

  • Example protocols: RIP, IGRP.

  • Simple but can suffer from problems like count-to-infinity and routing loops.

• Link State Routing Protocol A routing protocol where each router builds a complete map of the network topology by exchanging link-state information with all routers.

• Uses the Dijkstra algorithm.

• Example protocols: OSPF, IS-IS.

• More complex but faster convergence and avoids persistent loops.

• Distance Vector → Relies on neighbor updates, limited view.

• Link State → Relies on full network knowledge, global view.

• 
  

RIP (Routing Information Protocol)

RIP is one of the oldest dynamic routing protocols used in computer networks to help routers automatically share information about reachable networks.

Working Principle (Distance Vector Algorithm)

• RIP uses the Bellman‑Ford algorithm to calculate the best route.

• Each router shares its routing table with neighboring routers every 30 seconds.

• The metric used is hop count — each router hop adds 1 to the count.

• The maximum hop count is 15; anything beyond that is considered unreachable.

Version	Description
RIP v1	Classful routing (no subnet info)
RIP v2	Classless routing (supports subnet masks, authentication)
RIPng	RIP for IPv6 networks

Administrative Distance (AD) is the measure of trustworthiness of a routing information source.

• It is a numeric value between 0 and 255.

• Lower AD = more trusted route.

• Higher AD = less trusted route.

Routing Source	AD Value
Connected interface	0
Static route	1
External BGP (eBGP)	20
EIGRP (internal)	90
OSPF	110
IS-IS	115
RIP	120
EIGRP (external)	170
Internal BGP (iBGP)	200
Unknown/Untrusted	255

RIPv2 (Routing Information Protocol Version 2)

RIPv2 is an enhanced version of the original RIP (Routing Information Protocol), used in computer networks for dynamic routing.

Key Features of RIPv2

• Classless Routing → Supports subnet masks (CIDR), unlike RIPv1.

• Multicast Updates → Sends updates using 224.0.0.9 instead of broadcast, reducing unnecessary traffic.

• Update Interval → Routers exchange routing tables every 30 seconds.

• Routing Metric → Uses hop count as metric (max 15 hops; 16 = unreachable).

• Update Interval → Routers exchange routing tables every 30 seconds.

Timer Name	Default Value	Purpose
Update Timer	30 sec	Sends routing updates periodically
Invalid Timer	180 sec	Marks route as invalid if no update
Hold-Down Timer	180 sec	Prevents unstable route updates
Flush Timer	240 sec	Removes invalid routes from table

Router> enable Router# configure terminal Router(config)# router rip Router(config-router)# version 2 Router(config-router)# network 192.168.1.0 Router(config-router)# network 10.0.0.0 Router(config-router)# exit Router# show ip route

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