Network Devices

Outline

• Network devices
• Hub operation
• Switch / Bridge operation
• Router operation
• Difference between Switch & Bridge
• Collision domain
• Broadcast domain

Network Devices

• End-user devices include computers, printers, scanners, and other devices that provide services directly to the user.
• Hub, Switch, and Bridge are network devices — they connect nodes to form a network.
• Router is an internetwork device — it connects different networks together to form an internetwork.

✅ Important

• Same network → use Switch
• Different networks → use Router

Hub

• Hub is a Layer 1 device (Physical Layer)
• It does not understand MAC or IP address
• Also called dummy or non-intelligent device
• Cannot filter data
• Sends data to all ports (flooding)

Hub Environment is called

• Half duplex
• Shared bandwidth environment
• Ethernet network
• Collision domain
• IEEE 802.3 standard

Hub Operation

• Only one device can transmit at a time
• If two devices transmit → collision occurs
• Both frames are discarded
• A jam signal is sent
• Devices retransmit after random time (CSMA/CD)

✅ Added (Important for exam): Hub uses CSMA/CD (Carrier Sense Multiple Access with Collision Detection)

Flooding

When hub receives a frame:

• It sends frame to all ports

⚠️ Correction Your note said:

except the port it is received on

✅ Correct behavior of hub: Hub sends to ALL ports including incoming port (because it is just electrical repeat)

Switch & Bridge

• Switch and Bridge are Layer 2 devices (Data Link Layer)
• They filter data using MAC address
• MAC address = Layer 2 address
• They understand MAC only (not IP)
• They maintain MAC Address Table (CAM table)

Command:

show mac address-table

Switch & Bridge Environment

• Full duplex
• Dedicated bandwidth
• No collisions (in full duplex)
• Each device has dedicated link to switch

Switch Operation

When switch receives a frame:

Case A: MAC not in table

→ Switch floods frame

Case B: MAC in table

→ Switch forwards to specific port only

Important Switch Facts

• Switch is newer technology
• Mostly used today
• Each switch port = one collision domain
• All ports in same VLAN = one broadcast domain

Switch Types

Your notes:

• Static Switch Manageable
• Dynamic Switch Not Manageable

⚠️ Correction Correct classification:

Managed Switch

• Configurable
• VLAN support
• Security features

Unmanaged Switch

• Plug and play
• No configuration

Switch vs Bridge

Router

• Router is Layer 3 (Network Layer) device
• Filters data using IP address
• Connects different networks
• Uses Routing table
• Forwards packets between networks

When router receives packet:

• Reads destination IP
• Finds network in routing table
• Forwards packet

If network not found:

• Packet discarded
• OR sent to default route (if configured) ✅

Router Important Facts

• Each router port = separate network
• Each router port = separate broadcast domain
• Router blocks broadcast by default
• Router performs routing between networks

Main Functions of Router

• Packet switching
• Packet filtering
• Best path selection
• Internetwork communication
• Blocks broadcast

Collision Domain

A collision domain is:

A network segment where only one device can transmit at a time

Rules

Hub → 1 collision domain (all ports shared) Switch → Each port = 1 collision domain Router → Each port = 1 collision domain

Broadcast Domain

Broadcast domain is:

A network where broadcast reaches all devices

Rules

Hub → 1 broadcast domain Switch → 1 broadcast domain (default VLAN) Router → Each port = separate broadcast domain

Exam Shortcut Table

Very Important Exam Notes

• Hub = broadcast everything
• Switch = forward using MAC
• Router = forward using IP
• Switch breaks collision domain
• Router breaks broadcast domain
• Hub = half duplex
• Switch = full duplex
• Router = connects networks