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This lesson begins our deep dive into LAN switching logic and how a switch handles frame forwarding. We will explore how a switch receives, processes, and forwards Ethernet frames based on MAC address information.
A LAN switch forwards Ethernet frames between interfaces. To do this, a switch makes decisions based on the source and destination MAC addresses in Ethernet frames, whose structure is shown below.
Flow:
Computer → Switch → Router → ISP → Internet → Server → Router → Switch → Computer
| Type of Switch | Description | Used In |
|---|---|---|
| Unmanaged Switch | Simple plug-and-play switch with no configuration needed. | Homes, small offices |
| Managed Switch | Advanced switch with configuration, security, and monitoring features. | Businesses, schools, data centers |
| Smart Switch | Provides limited management features, easier to use than a managed switch. | Small to medium businesses |
| Layer 2 Switch | Works at the Data Link layer and uses MAC addresses for communication. | Local Area Networks (LAN) |
| Layer 3 Switch | Works with both MAC and IP addresses and can perform routing. | Large enterprise networks |
| PoE Switch | Provides both electrical power and data through one Ethernet cable. | IP cameras, VoIP phones, access points |
| Modular Switch | Allows adding extra modules or ports for expansion. | Large organizations, data centers |
| Fixed Configuration Switch | Comes with a fixed number of ports and cannot be expanded. | Small and medium networks |
If a company deploys unmanaged switches in its network, especially in a medium or large organization, it can face many serious problems related to security, performance, and management. An unmanaged switch works on plug-and-play principle and provides no control or configuration, which is risky for business networks.
In short,using unmanaged switches in a company network leads to security risks, slow performance, difficult troubleshooting, lack of control, and poor scalability, which can seriously affect business operations and productivity.
Deploying a managed switch in a company network provides many important benefits related to security, performance, control, and reliability. It is essential for medium and large organizations where many users, servers, and applications share the same network.
Finally, managed switches enable centralized management and policy control. Network settings can be configured and updated from one place, ensuring consistency across the company network. This makes the network more organized, secure, and easier to manage.
In summary, the main benefits of managed switch deployment in a company are strong security, higher performance, easy monitoring, better reliability, scalability, and full network control, which together create a stable and professional business network environment.
Managing a managed switch requires network knowledge because it needs proper configuration and setup to work efficiently. A user should understand networking concepts such as IP addressing, VLAN configuration, port settings, traffic management, and security controls. This knowledge helps in monitoring the network, troubleshooting problems, and using advanced features correctly. Without networking knowledge, it may be difficult to configure and manage a managed switch effectively.
Simple way to identify:
Console/MGMT Port present = Managed Switch
Only Ethernet ports = Unmanaged Switch
A managed switch can also be identified by special management ports. It often includes a Console Port and sometimes a Management (MGMT) Port.
An unmanaged switch normally does not have a Console Port or Management Port because it does not support configuration or remote management. It only has regular Ethernet ports for connecting devices.
Simple identification:
Managed switch = Ethernet ports + Console Port + MGMT Port + Configuration features
Unmanaged switch = Only Ethernet ports + No Console/MGMT Port + Plug-and-play
Here is a simple chart comparison between a managed switch and an unmanaged switch:
| Feature | Managed Switch | Unmanaged Switch |
|---|---|---|
| Configuration | Required | Not required |
| Setup | Complex | Very simple (plug-and-play) |
| Network Control | Full control | No control |
| VLAN Support | Yes | No |
| QoS (Traffic Priority) | Yes | No |
| Security Features | Advanced security available | Basic / none |
| Monitoring | Yes (network monitoring tools) | No |
| Remote Management | Yes | No |
| Console / MGMT Port | Available | Not available |
| Technical Knowledge | Required | Not required |
| Cost | Expensive | Low cost |
| Usage | Businesses, large networks | Homes, small networks |
| Performance | High and customizable | Basic performance |
| Troubleshooting | Advanced tools available | Very limited |
Summary:
Managed Switch = Advanced + Configurable + Secure
Unmanaged Switch = Simple + Plug-and-Play + Easy to use
Example of a Layer 2 Switch?
Example of a Layer 3 Switch?
Imagine a company has three departments: Sales, Accounts, and Human Resources (HR). Each department is placed in a separate VLAN with its own IP subnet:
This allows different departments to communicate while keeping each department’s network separate, organized, and secure.
In simple words:
Layer 2 Switch → Used for communication within the same network
Layer 3 Switch → Used for communication between different networks
| Feature | Layer 2 Managed Switch | Layer 3 Managed Switch |
|---|---|---|
| Working Layer | Works at Layer 2 (Data Link Layer) | Works at Layer 2 + Layer 3 (Network Layer) |
| Address Used | Uses MAC Address | Uses MAC Address + IP Address |
| Main Function | Switching data within same network | Switching + Routing between networks |
| Subnet Communication | Same subnet only | Same subnet + different subnets |
| Inter-VLAN Routing | Not supported | Supported |
| Network Size | Small / medium networks | Large enterprise networks |
| Speed | Fast local communication | Fast local + routing communication |
| Configuration | VLAN, QoS, security, monitoring | VLAN, QoS, security, monitoring + routing setup |
| Use Case | Office LAN, school lab, small business | Large office, campus, hospital, data center |
| Example | Communication in 192.168.1.0/24 subnet | Communication between 192.168.10.0/24 and 192.168.20.0/24 |
Simple Difference:
Layer 2 Managed Switch = Manage traffic in same network
Layer 3 Managed Switch = Manage traffic + route between different networks
In simple words:
Need Layer 3 Switch = To connect and route traffic between different networks/subnets efficiently.
1) Catalyst 1000 Series
Catalyst 1000 series is a small business managed switch. It is mainly used in small offices, shops, schools, and branch networks. This switch supports basic Layer 2 features like VLAN, STP, port security, and trunking. Some models also support PoE for IP phones, access points, and CCTV cameras. It is a low-cost and easy-to-manage switch.
2) Catalyst 1200 / 1300 Series
Catalyst 1200 and 1300 series are business-class managed switches. They provide Layer 2 switching and limited Layer 3 features. These switches support VLAN, QoS, security features, and PoE connectivity. They are suitable for medium-size office networks where better management and performance are needed.
3) Catalyst 2960 Series
Catalyst 2960 series is one of the most popular Cisco access switches. It is mainly a Layer 2 managed switch used for connecting computers, printers, IP phones, and wireless access points. It supports VLAN, trunk ports, STP, EtherChannel, and port security. Many companies used this model for office LAN access networks.
4) Catalyst 3560 Series
Catalyst 3560 is a Layer 3 switch. It can perform switching and routing in the same device. It supports static routing, inter-VLAN routing, and dynamic routing protocols like OSPF and EIGRP. This switch is commonly used in departments where routing between multiple VLANs is required.
5) Catalyst 3750 Series
Catalyst 3750 is an advanced stackable Layer 3 switch. Multiple switches can be connected together using stack cables and managed as one switch. This improves scalability, performance, and redundancy. It is used in enterprise networks where many users need high-speed and reliable connectivity.
6) Catalyst 3850 Series
Catalyst 3850 is a high-performance enterprise switch. It supports Layer 2 and Layer 3 networking, switch stacking, advanced security, and wireless controller features. It can manage wired and wireless network traffic together. This makes it useful in campus and enterprise environments.
7) Catalyst 9200 Series
Catalyst 9200 series is the modern replacement for older access switches like 2960. It offers stronger security, automation, better power efficiency, and advanced management features. It supports Layer 2 and Layer 3 features, PoE, stacking, and high-speed uplinks. It is widely used in modern office networks.
8) Catalyst 9300 Series
Catalyst 9300 series is one of Cisco’s most widely used enterprise access switches today. It provides high performance, advanced Layer 3 routing, strong security, stackability, and high-speed uplinks like 10G and 25G. It is commonly deployed in large office and campus networks.
9) Catalyst 9400 Series
Catalyst 9400 is a modular chassis switch. It uses supervisor modules, line cards, and redundant power supplies. This design allows expansion, high availability, and large port capacity. It is mainly used in distribution layer networks in large campuses and enterprises.
10) Catalyst 9500 Series
Catalyst 9500 is a fixed core switch designed for high-speed enterprise routing and switching. It supports 10G, 25G, 40G, and 100G connectivity. It provides very high throughput, security, and automation features. It is mostly used in core layer networks.
11) Catalyst 9600 Series
Catalyst 9600 is a high-end modular core switch built for very large enterprise networks. It delivers maximum performance, very high bandwidth, and strong redundancy. It supports advanced routing, security, and large-scale network operations. It is commonly used as a backbone switch in big organizations.
Cisco Core Layer Switch Models:
The Cisco Catalyst 9500 Series is a high-performance fixed-core switch designed for enterprise campus networks. It is widely used as a core layer switch because it offers very fast switching speeds, low latency, and advanced Layer 3 routing capabilities. It supports uplinks ranging from 10 Gigabit to 100 Gigabit Ethernet, making it suitable for organizations with heavy network traffic. It also includes security features, automation support, and redundancy options, which help keep the network reliable and always available. For medium to large enterprises, this is one of Cisco’s most common core switches.
The Cisco Catalyst 9600 Series is a modular chassis-based switch built for very large enterprise networks. Unlike fixed switches, it allows network engineers to add different line cards and modules depending on network requirements. This makes it highly scalable and flexible. It supports high-density 10G, 25G, 40G, and 100G connections, and it includes redundant supervisors, power supplies, and cooling systems for maximum uptime. Because of its powerful hardware and modular design, it is commonly deployed in university campuses, financial institutions, and large corporate headquarters where network downtime is unacceptable.
The Cisco Nexus 9000 Series is mainly designed for data center core and cloud networking environments. It provides extremely low latency, very high throughput, and support for modern technologies such as virtualization, software-defined networking (SDN), and automation. It supports high-speed interfaces ranging from 10G to 400G, making it ideal for connecting servers, storage systems, and large-scale cloud infrastructure. Organizations that run data centers or private cloud environments often choose Nexus 9000 switches because of their performance, scalability, and advanced data center features.
The Cisco Catalyst 6800 Series is an older but still powerful core switch platform used in many enterprise campus networks. It is chassis-based and provides large port density, strong Layer 3 routing, and reliable high-speed connectivity between distribution and access layers. Although newer Catalyst 9000 models have largely replaced it, the 6800 Series remains in operation in many established organizations because of its stability and proven performance. It was widely used as a core backbone switch in large offices and enterprise networks.
The Cisco Nexus 7000 Series is a high-end modular core switch built for very large data centers, service providers, and enterprise backbone networks. It offers massive scalability, high port density, and extremely fast forwarding performance. It supports redundant supervisors, multiple line cards, and advanced network services, making it suitable for mission-critical environments. Because of its carrier-grade design, it is often used in large ISPs, banking networks, and enterprise data centers where maximum performance and reliability are required.
A distribution switch is the middle layer switch in the three-tier network design (Access → Distribution → Core). It works as the connection point between access layer switches and the core layer switch. The main job of a distribution switch is to collect traffic from multiple access switches, apply network policies, and forward traffic to the core layer. It performs functions such as routing between VLANs (Inter-VLAN Routing), access control lists (ACLs), Quality of Service (QoS), security policies, and redundancy. Because of these functions, the distribution layer is often called the policy layer of the network.
The Cisco Catalyst 9300 Series is one of the most common switches used in the distribution layer of enterprise campus networks. It is a fixed, stackable Layer 3 switch that supports high-speed uplinks such as 10G, 25G, and 40G. It provides strong routing performance, advanced security features, automation support, and redundancy options. Because multiple Catalyst 9300 switches can be stacked together and managed as one unit, it offers scalability and simplified network management, making it suitable for medium and large organizations.
The Cisco Catalyst 9400 Series is a modular chassis-based switch designed for larger distribution layer deployments. It offers high port density, modular expansion, and redundant supervisor engines for high availability. This switch is ideal for organizations that need a scalable and reliable distribution layer, such as universities, hospitals, and large office campuses. It supports advanced Layer 3 routing, policy enforcement, and secure network segmentation.
The Cisco Catalyst 9500 Series can also be used in the distribution layer, especially in high-performance campus networks. It is often deployed where very fast uplinks to the core are needed, such as 40G or 100G connections. Its strong Layer 3 routing capabilities, security, and automation features make it suitable as either a high-end distribution switch or a smaller network’s core switch.
The Cisco Catalyst 3850 Series is an older generation switch that was widely used in the distribution layer. It supports Layer 3 routing, stacking, and enterprise security features. Although newer Catalyst 9000 Series switches have replaced it in many deployments, it is still found in existing enterprise networks because of its reliability and solid performance.
Simple understanding:
An access switch is the first layer in a three-tier network design (Access → Distribution → Core). It is the switch that directly connects end-user devices such as computers, printers, IP phones, wireless access points, CCTV cameras, and other network devices. The main purpose of the access layer is to provide network connectivity to users and devices while also applying basic network policies such as VLAN assignment, port security, PoE (Power over Ethernet), authentication (802.1X), and Quality of Service (QoS). Access switches are designed to provide many user ports, easy management, and reliable connection to the distribution layer.
The Cisco Catalyst 9200 Series is one of the most common access switches used in enterprise networks. It is designed for secure and reliable access layer connectivity, offering 24-port and 48-port models with Gigabit Ethernet interfaces. Many models support PoE or PoE+, which allows devices like IP phones, wireless access points, and cameras to receive power directly through the network cable. It also supports Layer 2 switching, limited Layer 3 features, VLANs, security policies, and uplinks to distribution switches using 1G, 10G, or higher-speed connections.
The Cisco Catalyst 9300 Series is a higher-performance switch that can also be used in the access layer, especially in large enterprise environments. It offers stacking capability, advanced security, automation, and high-speed uplinks. It supports full PoE, multigigabit ports for Wi-Fi 6/6E access points, and advanced Layer 3 routing. Because of its flexibility, many organizations use it as a premium access switch or even as a distribution switch.
The Cisco Catalyst 1000 Series is an entry-level access switch designed for small businesses and branch offices. It provides basic Layer 2 switching, VLAN support, PoE options, and simple management features. It is a cost-effective solution for networks that do not require advanced routing or enterprise-level automation.
The Cisco Catalyst 2960-X Series is an older access switch model that was widely deployed in enterprise networks. It offers reliable Layer 2 switching, Gigabit Ethernet ports, PoE support, VLAN configuration, and strong security features. Although newer Catalyst models have replaced it in many networks, it is still commonly found in existing installations because of its proven stability.
Example All Card
Server A
↓
Port 1
↓
Line Card 1
↓
Supervisor Card decides path
↓
Fabric Card transports packet
↓
Line Card 5
↓
Port 10
↓
Server B
Example: A company starts with a modular switch having 24 ports. Later, when more devices are added, the company installs another 24-port module, increasing capacity to 48 ports without buying a new switch.
Some common Cisco modular switch models are:
Example model names:
• Cisco Catalyst C9407R
• Cisco Catalyst C9410R
• Cisco Catalyst C9606R
• Cisco Catalyst WS-C4507R+E
• Cisco Catalyst 6509-E
These are common Cisco modular switches used in professional and enterprise networks.
Example: A company may install a chassis switch with 48 ports at first. As the company grows, it can add more line cards to increase to 96 or 144 ports without replacing the whole switch.
Simple:
Line Card = Provides ports for network connections
Supervisor Card = Controls and manages the whole switch
Example of Line Card and Supervisor Card?
Imagine a large company uses a Cisco chassis switch in its main network room. Inside the chassis:
A Supervisor Card (Sup Card) is installed in the supervisor slot. This card acts like the brain of the switch. It controls configuration, routing, security policies, traffic management, and overall switch operation.
Two Line Cards are installed in separate slots:
When a computer sends data, the line card receives the data through its port, and the supervisor card processes the switching/routing decision. Then the data is forwarded through the correct line card port to the destination device.
Simple example:
Line Card = Ports for connecting devices
Supervisor Card = Brain that manages all network traffic
Example: A company data center with hundreds of servers may use a Cisco Nexus switch to connect servers, storage devices, and routers with high-speed fiber links for fast data transfer.
Simple:
Nexus Switch = High-speed data center switch for large enterprise networks
Cisco Nexus switch price in India is expensive compared with refurbished units.
Examples:
Example: A security camera installed on a ceiling can receive power + network data from a PoE switch using just one Ethernet cable, so no separate electrical wiring is needed.
Simple:
PoE Switch = One Ethernet cable carries both power and data
Switch Stacking Example?
When two core switches are stacked?
One major benefit is high availability. If one core switch fails, the other switch in the stack continues to handle traffic without network downtime. Another benefit is load sharing, where traffic from access switches (like floor switches) can use both core switches simultaneously, improving overall bandwidth and performance. It also reduces STP complexity because the stack is treated as a single switch, so there is no blocking between the two core devices.
In a multi-floor building, each floor usually has an access switch. These floor switches are connected to the stacked core switches. With stacking, you can distribute uplinks intelligently—for example, Floor 1 switch connects to Core Switch A, Floor 2 switch connects to Core Switch B, and Floor 3 switch can use both links for redundancy. Since both core switches are acting as one logical device, traffic automatically balances and switches between links if one path fails.
Two core switches in stack = one powerful brain of the network, and all floor switches connect to it like branches of a tree, ensuring smooth communication across the building.
