Trunking (VLAN Communication Between Switches)

📌 What is Trunking?

A trunk port is a switch port that carries traffic for multiple VLANs using 802.1Q tagging.

👉 Simple:

“One cable, multiple VLANs”

🎯 What You Will Learn

• VLAN communication across switches
• 802.1Q tagging
• Access vs Trunk port difference

🧪 Lab Setup (Build in Cisco Packet Tracer)

🔹 Topology

• 2 Switches (2960)
• 4 PCs

🔹 VLAN Plan

⚙️ Step 1: Assign IP Addresses

⚙️ Step 2: Create VLANs on BOTH Switches

Do this on Switch0 and Switch1

enable
configure terminal

vlan 10
name HR

vlan 20
name IT

exit

switch 0

switch 1

⚙️ Step 3: Assign Access Ports

🔹 Switch0

interface fa0/1
switchport mode access
switchport access vlan 10

interface fa0/2
switchport mode access
switchport access vlan 20

🔹 Switch1

interface fa0/1
switchport mode access
switchport access vlan 10

interface fa0/2
switchport mode access
switchport access vlan 20

⚙️ Step 4: Configure Trunk Port (MOST IMPORTANT)

Assume connection between switches is:

• Switch0 → Fa0/24
• Switch1 → Fa0/24

🔹 On BOTH switches:

interface fa0/24
switchport mode trunk

🧪 Step 5: Test Connectivity

✅ Same VLAN Across Switches (Should Work)

From PC0:

ping 192.168.10.2

✔ Success

❌ Different VLAN (Should Fail)

From PC0:

ping 192.168.20.2

❌ Failed (no routing yet)

If still facing issue 

✅ Step-by-Step Fix

🔌 1. Check Physical Connection (MOST IMPORTANT)

Make sure:

👉 You connected:

Switch0 Fa0/24 → Switch1 Fa0/24

✔ Use Copper Straight-Through

👉 If unsure:

• Delete cable
• Reconnect properly

🔄 2. Check Both Sides

Both ends must be connected:

• Switch0 Fa0/24 ✅
• Switch1 Fa0/24 ✅

👉 If one side is not connected → port stays DOWN

⚙️ 3. Enable Port (Just in case)

Run on BOTH switches:

• enable
• configure terminal
• interface fa0/24
• no shutdown

🔍 What Happens Internally?

• PC0 sends packet → Switch0
• Switch0 adds VLAN tag (802.1Q)
• Packet goes through trunk
• Switch1 reads VLAN tag
• Forwards to correct VLAN port

⚠️ Key Concepts (Very Important)

🔹 Access Port

Carries one VLAN only

🔹 Trunk Port

Carries multiple VLANs

🔹 VLAN Tagging

• Switch adds VLAN ID inside frame
• Helps identify which VLAN packet belongs to

⚠️ Common Mistakes

• ❌ VLAN not created on both switches
• ❌ Trunk not configured on both sides
• ❌ Wrong port numbers
• ❌ IP mismatch

❓ What protocol is used?

👉 IEEE 802.1Q

❓ Difference between access & trunk?

Access → single VLAN

Trunk → multiple VLANs

❓ Why trunking is needed?

👉 To connect multiple switches while maintaining VLAN separation

🧠 Real-World Example

Company has:

• Multiple floors
• Multiple switches

👉 VLANs must travel between switches

➡️ Trunking is used

NOTE - In Cisco Packet Tracer labs and real-world configurations, VLAN 99 is a common industry-standard placeholder used for two specific administrative purposes:

1. Management VLAN: It is frequently used to host the switch's Management IP address. By moving management traffic (SSH, Telnet, SNMP) to a dedicated VLAN like 99, you keep it separate from regular user data, which is a major security best practice.
2. Native VLAN: It is often designated as the Native VLAN on trunk links. The Native VLAN is responsible for handling all "untagged" traffic that passes through a trunk port.

Why use 10 and 20 instead of the default?

By default, Cisco switches use VLAN 1 for both management and native traffic. However, using the default is considered a security risk because:

1. VLAN Hopping: Attackers can exploit the default VLAN 1 to jump between different networks.
2. Control Traffic: Standard control protocols (like CDP or VTP) often use VLAN 1. Moving user and management data to a different ID like 99 prevents these streams from mixing.

Key Rules for VLAN 10 and 20

• Consistency: If you set VLAN 99 as the native VLAN on one switch, you must set it on the other side of the trunk as well. If they don't match, you will see a native VLAN mismatch error, which can cause connectivity issues.
• Logical ID: There is nothing "magic" about the number 99; it is just a common convention. You could technically use 100, 777, or any other valid ID.

✅ Why ping 192.168.10.2 WORKS

Because:

👉 PC0 and PC2 are in same VLAN (VLAN 10)

Even though they are on different switches:

• Trunk carries VLAN 10 traffic
• Switches forward frames based on MAC
• No routing needed

✔ So it works

❌ Why ping 192.168.20.2 FAILS from PC0

Because:

• 👉 PC0 is in VLAN 10
• 👉 PC3 is in VLAN 20

These are different networks

🔥 Simple Analogy (Very Important)

Think like this:

VLAN 10 = Room A

VLAN 20 = Room B

• 👉 Switch = hallway
• 👉 Trunk = connecting hallway between buildings

Case 1 (Working)

PC0 → PC2

Room A → Room A

✔ Allowed

Case 2 (Failing)

PC0 → PC3

Room A → Room B

❌ Door is closed (no router)

🎯 Core Rule

• 👉 Switch = Layer 2 → only works inside same VLAN
• 👉 Router = Layer 3 → required between VLANs

NOTE - Now the question is if “PC1 (192.168.20.1) is in same switch as PC0, so why not ping?”

• 👉 Same switch does NOT matter
• 👉 VLAN matters

So: 

Why ping between VLANs fails?

Answer:

Because switches operate at Layer 2 and cannot route traffic between different VLANs. Inter-VLAN routing requires a Layer 3 device like a router.

✅ What You Need to Do

To make this work:

👉 You must configure Inter-VLAN Routing so for this visit our another blog.

Disclaimer

VLAN (Virtual LAN) — Practical + Interview Guide

Definition (say this in interviews):

A VLAN (Virtual Local Area Network) is a logical segmentation of a Layer 2 network that separates devices into different broadcast domains on the same physical switch.

👉 In simple terms:

“Same switch, but different networks.”

🎯 What You Will Learn

• Network segmentation
• Broadcast isolation
• Basic switch configuration
• Real office network concept

🧪 Lab Setup (Build This in Cisco Packet Tracer)

🔹 Topology

• 1 Switch (2960)
• 4 PCs

🔹 VLAN Plan

⚙️ Step 1: Assign IP Addresses

• PC0 → 192.168.10.1
• PC1 → 192.168.10.2
• PC2 → 192.168.20.1
• PC3 → 192.168.20.2

Subnet mask: 255.255.255.0

⚙️ Step 2: Create VLANs on Switch

Go to Switch → CLI

enable
configure terminal

vlan 10
name HR

vlan 20
name IT

exit

⚙️ Step 3: Assign Ports to VLANs

Assume:

• PC0 → Fa0/1
• PC1 → Fa0/2
• PC2 → Fa0/3
• PC3 → Fa0/4

interface fa0/1
switchport mode access
switchport access vlan 10

interface fa0/2
switchport mode access
switchport access vlan 10

interface fa0/3
switchport mode access
switchport access vlan 20

interface fa0/4
switchport mode access
switchport access vlan 20

🧪 Step 4: Test Connectivity

✅ Same VLAN (Should Work)

From PC0:

ping 192.168.10.2

✔ Success

❌ Different VLAN (Should Fail)

From PC0:

ping 192.168.20.1

❌ Request timed out

🔍 What You Just Learned (IMPORTANT)

VLAN 10 and VLAN 20 are separate broadcast domains

Switch does NOT allow communication between VLANs

Even though:

• Same switch
• Same cable

👉 Still isolated

Simulation

⚠️ Common Mistakes

• ❌ Forgetting switchport mode access
• ❌ Wrong port mapping
• ❌ Same IP network for all PCs

🎯 Interview Questions (Must Know)

❓ What is VLAN?

👉 Logical segmentation of network at Layer 2.

❓ Why VLAN is used?

• Security
• Performance
• Broadcast control

❓ Can VLANs communicate?

👉 No, unless:

➡️ Inter-VLAN Routing is configured

❓ VLAN works on which layer?

👉 Layer 2 (Data Link)

🧠 Real-World Example

Office:

• HR department → VLAN 10
• IT department → VLAN 20

👉 They are isolated for:

• Security
• Traffic control

Disclaimer

Repeater Practical in Cisco Packet Tracer (Step-by-Step Guide)

In networking, maintaining signal strength over long distances is a fundamental challenge. This is where a repeater comes into play. In this practical, we will understand how a repeater works and simulate it using Cisco Packet Tracer.

📌 What is a Repeater?

A repeater is a networking device that operates at the Physical Layer (Layer 1) of the OSI model and in first port its getting signal and in second port regenerate the signal and send to the receiver.

Definition:

A repeater receives a weak or corrupted signal, regenerates it, and retransmits it to extend the network distance.

🔍 Key Features of Repeater

• Works on Layer 1 (Physical Layer)
• Does not understand IP or MAC addresses
• Only regenerates signals
• Used to extend network range
• Cannot filter or route data

🧪 Lab Overview (Your Topology)

From your setup:

• Two switches connected via a Repeater
• Each switch connects to multiple PCs

All devices are in the same network:

10.10.10.0/24

🖥️ IP Addressing

🎯 Objective

• Understand how a repeater extends network connectivity
• Enable communication between two switches
• Test connectivity between distant PCs
• Observe signal regeneration

🛠️ Step 1: Create Topology

Open Cisco Packet Tracer

Add:

• 2 Switches (2960)
• 1 Repeater
• 6 PCs
• Connect:
• PCs → Switches
• Switches → Repeater

👉 Use Copper Straight-Through Cable

🌐 Step 2: Configure IP Addresses

Assign IPs manually:

All PCs in same subnet: 10.10.10.0/24

Subnet mask: 255.255.255.0

👉 No default gateway needed (no router)

📡 Step 3: Test Connectivity

From PC0 → Command Prompt:

ping 10.10.10.6

👉 Expected Result:

✔ Successful reply

🎬 Step 4: Use Simulation Mode

• Switch to Simulation Mode
• Enable all filters
• Run ping again
• Click Auto Capture / Play

🔍 What Happens Internally?

1️⃣ Signal Travels from PC0

Data sent to Switch0

2️⃣ Repeater Regenerates Signal

Receives weak signal

Cleans and retransmits it

3️⃣ Signal Reaches Switch1

Delivered to destination PC (PC5)

⚠️ Important Observations

• Repeater does not filter traffic
• Entire network remains a single collision domain
• All devices share bandwidth

❌ Limitations of Repeater

• No intelligence (cannot make decisions)
• Cannot reduce network traffic
• Cannot improve security
• Rarely used in modern networks

🔄 Repeater vs Hub vs Switch

🧠 Real-World Use

Repeaters are used in:

• Long-distance cable networks
• Fiber optic communication
• Legacy Ethernet setups

👉 In modern networks, switches and routers have replaced repeaters.

💡 Conclusion

This practical demonstrates how a repeater helps extend network distance by regenerating signals. While it plays a foundational role in networking, it lacks intelligence and is rarely used today. Understanding repeaters builds a strong base for learning advanced networking devices like switches and routers.

Router + Switch Integration in Cisco Packet Tracer (Step-by-Step Practical Guide)

If you want to move beyond basic LAN setups, integrating a router with multiple switches is a crucial skill. In this lab, we connect two different networks using a router and enable communication between them using Cisco Packet Tracer.

📌 Lab Overview

This practical demonstrates:

• Two separate LANs
• Each LAN connected to a switch
• Both switches connected to a central router
• Inter-network communication using routing

🧪 Network Topology (From Your Setup)

🔹 LAN 1

Network: 10.0.0.0/8

Devices:

• PC0 → 10.0.0.1
• PC1 → 10.0.0.2
• PC2 → 10.0.0.3

Connected to Switch0

🔹 LAN 2

Network: 192.168.1.0/24

Devices:

• PC3 → 192.168.1.1
• PC4 → 192.168.1.2
• PC5 → 192.168.1.3

Connected to another switch

🔹 Router Configuration

Router (2911) interfaces:

• G0/0 → 10.0.0.4
• G0/1 → 192.168.1.4

👉 This router acts as a gateway between both LANs

🎯 Objective

• Enable communication between LAN1 and LAN2
• Configure router interfaces
• Set default gateways on PCs
• Verify connectivity using ping

🛠️ Step 1: Configure Router Interfaces

Click router → CLI and run:

enable
configure terminal

interface gigabitEthernet 0/0
ip address 10.0.0.4 255.0.0.0
no shutdown

interface gigabitEthernet 0/1
ip address 192.168.1.4 255.255.255.0
no shutdown

end

👉 This activates both interfaces

🌐 Step 2: Configure Default Gateway on PCs

This is the most important step for inter-network communication.

🔹 LAN 1 PCs

Default Gateway → 10.0.0.4

🔹 LAN 2 PCs

Default Gateway → 192.168.1.4

📍 Path:

PC → Desktop → IP Configuration

🔌 Step 3: Verify IP Addressing

Make sure:

• All PCs in LAN1 use 10.0.0.x
• All PCs in LAN2 use 192.168.1.x
• Subnet masks are correct

📡 Step 4: Test Connectivity

🔹 Same Network Test

From PC0:

ping 10.0.0.3

👉 Should work (same LAN)

🔹 Cross Network Test (Important)

From PC0:

ping 192.168.1.1

👉 If configured correctly:

✔ Request will go → Switch → Router → Switch → PC3

🎬 Step 5: Use Simulation Mode

• Switch to Simulation Mode
• Enable all filters
• Run ping again
• Click Auto Capture / Play

🔍 What Happens Internally?

1️⃣ PC Sends Packet to Gateway

PC0 sees destination is different network

Sends packet to default gateway (router)

2️⃣ Router Processes Packet

Checks routing table

Forwards packet to correct interface

3️⃣ Packet Reaches Destination Network

Router → Switch → Target PC

⚠️ Common Mistakes

• ❌ Forgetting default gateway
• ❌ Not using no shutdown on router interfaces
• ❌ Wrong subnet mask
• ❌ Incorrect IP addressing

🔄 Real-World Use Case

This setup is used in:

• Office networks (different departments)
• Campus networks
• Enterprise environments

👉 Router connects multiple networks, switches connect devices within a network.

🧠 Key Concepts You Learned

• Routing between different networks
• Role of default gateway
• Router interface configuration
• Packet flow across networks

💡 Conclusion

This practical shows how a router enables communication between multiple LANs. While switches handle local traffic efficiently, routers make inter-network communication possible, forming the backbone of real-world networking.

Switch Practical in Cisco Packet Tracer (Step-by-Step Guide for Beginners)

If you’ve already learned hub networking, the next step is understanding how a network switch works. In this practical guide, you’ll build a simple LAN using a switch in Cisco Packet Tracer and observe how intelligent data forwarding improves network performance.

📌 What is a Switch?

A switch is a networking device that operates at the Data Link Layer (Layer 2) of the OSI model.

👉 Key features:

• Uses MAC address table for forwarding
• Sends data only to the intended device
• Reduces network traffic
• Supports full-duplex communication
• Creates separate collision domains per port

🧪 Lab Objective

• Create a LAN using a switch
• Connect multiple PCs
• Configure IP addresses
• Test connectivity using ping
• Observe packet flow in simulation mode
• Compare behavior with a hub

🛠️ Requirements

• Cisco Packet Tracer installed
• Basic knowledge of IP addressing

🔌 Step 1: Create Network Topology

Open Packet Tracer

Drag and drop:

1 Switch (e.g., 2960)

6 PCs (PC0 to PC5)

Connect all PCs to the switch using:

Copper Straight-Through Cable

👉 This forms a star topology, similar to hub setup but smarter.

🌐 Step 2: Configure IP Addresses

Assign IP addresses manually:

📍 Path:

PC → Desktop → IP Configuration

👉 No default gateway required for same network communication.

📡 Step 3: Test Connectivity

Go to PC0 → Command Prompt:

ping 192.168.1.6

👉 You should receive successful replies.

🎬 Step 4: Enable Simulation Mode

• Click Simulation Mode
• Click Edit Filters
• Click Show All / Enable All

👉 This ensures ARP and ICMP packets are visible.

📦 Step 5: Observe Packet Flow

Run the ping again and click:

Auto Capture / Play (▶▶)

OR

Capture/Forward (▶)

🔍 What Happens Behind the Scenes?

1️⃣ ARP Request (Broadcast)

PC0 asks: Who has 192.168.1.6?

Switch forwards to all devices (initially)

2️⃣ MAC Address Learning

Switch learns:

PC0 MAC → Port X

PC5 MAC → Port Y

👉 Stored in MAC Address Table

3️⃣ ICMP Packet (Smart Forwarding)

After learning:

Switch sends packet:

PC0 → Switch → PC5 ONLY

👉 Unlike a hub, it does NOT broadcast to all devices.

⚠️ Important Observations

• First communication involves broadcast (ARP)
• After learning, communication becomes direct and efficient
• Network traffic is significantly reduced

🔄 Switch vs Hub (Practical Difference)

🧠 Real-World Importance

Switches are widely used in:

• Office networks
• Data centers
• Enterprise environments

👉 They are the backbone of modern LANs.

🚀 Mini Practice Task

• Run ping PC0 → PC5
• Clear simulation
• Run ping again

👉 Observe:

• First ping = broadcast + learning
• Second ping = direct communication

💡 Conclusion

This practical demonstrates how a switch intelligently forwards data using MAC addresses, reducing unnecessary traffic and improving network efficiency. Compared to hubs, switches offer better performance, scalability, and security, making them essential in real-world networking.

Hub Practical in Cisco Packet Tracer (Step-by-Step Guide for Beginners)

If you're starting your networking journey, understanding how a hub works is fundamental. In this practical guide, we’ll build a simple network using a hub in Cisco Packet Tracer and observe how communication happens between devices.

📌 What is a Hub?

A hub is a basic networking device that operates at the Physical Layer (Layer 1) of the OSI model.

👉 Key characteristics:

• Broadcasts data to all connected devices
• No intelligence (doesn’t store MAC addresses)
• Works in half-duplex mode
• Creates a single collision domain

🧪 Lab Objective

• Create a network using a hub
• Connect multiple PCs
• Configure IP addresses
• Send data from one PC to another
• Observe packet flow using simulation

🛠️ Requirements

• Cisco Packet Tracer installed
• Basic understanding of IP addressing

🔌 Step 1: Create Network Topology

1. Open Packet Tracer

2. Drag and drop:

   # Hub

   # PCs (PC0 to PC5)

3. Connect all PCs to the hub using:

   # Copper Straight-Through Cable

👉 Your topology should look like a star network with a hub at the center.

🌐 Step 2: Configure IP Addresses

Assign IP addresses manually to each PC:

📍 Path:

Click PC → Desktop → IP Configuration

👉 No default gateway needed (no router involved)

📡 Step 3: Test Connectivity

Go to PC0 → Command Prompt and run:

ping 192.168.1.6

👉 If configured correctly, you’ll receive replies.

🎬 Step 4: Enable Simulation Mode

Click Simulation Mode (bottom right)

Click Edit Filters

Click Show All / Enable All

👉 This step is critical—without enabling protocols like ARP and ICMP, packets won’t be visible.

📦 Step 5: Observe Packet Flow

Now run the ping again and click:

#. Auto Capture / Play (▶▶)

OR

#. Capture/Forward (▶)

🔍 What Happens Behind the Scenes?

1️⃣ ARP Request (Broadcast)

PC0 asks: Who has 192.168.1.6?

Hub sends this request to all PCs

2️⃣ ARP Reply

PC5 responds with its MAC address

3️⃣ ICMP (Ping)

Actual communication occurs

👉 You’ll see packets traveling across all connections due to hub behavior.

⚠️ Important Observations

• All devices receive the data (not just the destination)
• Network traffic increases unnecessarily
• Collisions may occur

❌ Limitations of Hub

• No security
• No traffic filtering
• Poor performance
• Outdated technology

🔄 Hub vs Switch (Quick Comparison)

🚀 Conclusion

This practical demonstrates how a hub blindly forwards data to all connected devices. While hubs are no longer used in modern networks, understanding them builds a strong foundation for learning switches and advanced networking concepts.

Microsoft-365-L1-Desktop-Support-guide

This article is designed as a practical,User account disablement is a common L1-level ticket in enterprise environments. It may occur due to HR actions, security policy enforcement, inactivity, or administrative changes. L1 engineers must verify the reason carefully before enabling the account to avoid policy violations. This guide explains the standard enterprise workflow for handling disabled user accounts using Active Directory.

I will write article on each topic for single single blog -

I’ll break into real helpdesk categories:

1. Unlock user
2. Reset password
3. Enable / Disable account
4. Create new user
5. Add user to group
6. Remove user from group
7. Check login issues
8. Move user to correct OU
9. Basic permission via groups

Today we will see step by step Account & License Management  

👤 SCENARIO 1 — Enable / Disable account

 
🚫 SCENARIO — User Account Disabled


User account disablement is a common L1-level ticket in enterprise environments. It may occur due to HR actions, security policy enforcement, inactivity, or administrative changes. L1 engineers must verify the reason carefully before enabling the account to avoid policy violations.

This guide explains the standard enterprise workflow for handling disabled user accounts using Active Directory.


🔎 Symptoms Observed

• Users typically report:
• Cannot login to system
• Error message: “Your account has been disabled. Please contact your system administrator.”
• Outlook not connecting
• VPN authentication failing
• Teams login failure

1️⃣ Step 1 — Verify the Scenario (Important)

Before enabling the account, confirm:

Is this a rejoining employee?

Has HR approved account activation?

Is there an open service request ticket?

Was the account disabled due to security reasons?

Is this part of offboarding process?

⚠ Never enable an account without proper authorization.

2️⃣ Step 2 — L1 Action (Enable / Disable Account Procedure)

🖥 Using Active Directory Users and Computers (ADUC)

Method 1 — Via Properties

• Open ADUC
• Search for the user
• Right-click → Properties
• Go to Account tab
• Uncheck: Account is disabled
• Click Apply → OK

Method 2 — Quick Right-Click Option

• Open ADUC
• Locate the user
• Right-click on user

Select:

• ✔ Enable Account (if disabled)
• ✔ Disable Account (if requested by HR/Security)
• This is the fastest method used in L1 operations.

3️⃣ After Enabling — Inform the User

• Advise the user to:
• Lock PC (Windows + L)
• Log in again
• Connect VPN if working remotely
• Restart system if required
• If password expired, perform password reset as per policy.

4️⃣ When L1 Should Disable an Account

• L1 may disable accounts in cases such as:
• HR termination ticket
• Long leave request
• Security instruction
• Contract completion
• Lost device security precaution
• Always document ticket number and approval source.

🚨 Escalate If

• Immediately escalate to L2 / Security / HR if:
• Account disabled due to HR termination
• Security suspension case
• Insider threat investigation
• Legal hold case
• Unknown disablement with no ticket reference
• Account automatically re-disables (possible GPO or sync issue)

🧠 Real Helpdesk Insight

• In hybrid environments (On-Prem AD + Azure AD sync):
• If account is enabled in AD but still blocked in Microsoft 365
• Check Azure AD sync status
• Confirm sign-in status in Microsoft 365 Admin Center
• Sometimes cloud sign-in may be blocked separately.

✅ L1 Checklist (SOP Format)

• ✔ Identity verified
• ✔ Ticket approved
• ✔ Checked reason for disablement
• ✔ Account enabled via ADUC
• ✔ User informed
• ✔ Login tested
• ✔ Escalated if policy-related

🎯 Interview-Ready Statement

If interviewer asks how you handle disabled account cases:


“First, I verify the reason for disablement through ticket and HR approval. I never enable accounts without authorization. After validation, I enable the account via ADUC either through Properties → Account tab or right-click enable option. Then I guide the user to log in and monitor for replication issues. If the disablement is related to HR or security, I escalate immediately.”

Disclaimer