Lecture 9 – Switching & Cisco Devices Internals
Engr_Asad Khan 8/4/2025
1. Layer -1 device.
2. Just provide connectivity by receiving and forwarding bits.
3. Non intelligent device.
4. Single broadcast domain: all kind of packets are broadcast means
sends to all.
Engr_Asad Khan 8/4/2025
5. Single collision domain:
( A network in which more then two devices cant sends
packets at same time otherwise collision occurs).
5. Speed: 10 Mbps, Duplex: half.
Engr_Asad Khan 8/4/2025
HUB Limitations:
1. LAN congestion.
2. Slow speed.
3. Low network performance.
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BRIDGE
1. Breakup collision domain of HUB.
2. Layer-2 device.
3. Read MAC address.
4. Build software based MAC table.
Engr_Asad Khan 8/4/2025
SWITCH
1. Layer 2 and layer 3.
2. L2 Models: 2950,2960, 300.
3. L3 Models:
3550,3560,3750,3850,4500,6500,7000,9200,9300, 9500.
4. Manageable and Non manageable.
5. L2 can read only MAC add while L3 can read both IP and
MAC Add.
6. Single broadcast domain and Multiple collision domain.
7. Intelligent device due to ASIC.
8. Can build MAC and Routing Table.
9. Speed upto100 Gbps Duplex Full.
Engr_Asad Khan 8/4/2025
Layer-2 Switch:
1. Faster then layer-3.
2. Only reads MAC address.
3. Build MAC Table.
4. Low cost then Layer-3 switch.
Layer-3 Switch:
1. Provides all Layer-2 functionalities.
2. Reads IP address.
3. Build Routing Table.
4. Internetwork communication.
5. Policies.
6. Filtration.
7. L-3 redundancy.
Engr_Asad Khan 8/4/2025
Blade Switches
Campus LAN Switches (Access/ Compact)
Campus LAN Switches (Core / Distribution)
Data Center Switches
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ROUTER
1. Layer-3 device.
2. Can read IP and MAC address.
3. Build MAC Table and Routing Table.
4. Breakup Broadcast and Collision domain.
5. Internetwork communication.
6. Path selection.
7. Packet switching.
8. Packet filtering.
Engr_Asad Khan 8/4/2025
Branch Routers
Cloud Connectors
Cloud Edge
Data Center Interconnect Platforms
Industrial Routers and Gateways
Network Functions Virtualization
Service Provider Core Routers
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Switch & Router External Components:
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Cisco Devices Internal Components:
CPU: Called Central Processing Unit.
Used to execute instructions.
Take decisions.
RAM: Random Access Memory.
Called Volatile/Temporary Memory.
Stores MAC Table, Routing Table, ARP Table.
Stores Running IOS files.
Stores Running Configuration File.
Erased upon reloading.
NV-RAM: Called Non Volatile Random Access Memory.
Non Volatile / Permanent Memory.
Stores Startup / saved configuration file.
Stores configure register value.
Not Erased upon reloading.
Engr_Asad Khan 8/4/2025
ROM: Read Only Memory.
Stores programs to start and maintain device.
Stores POST program.
Stores Boot Strap program.
Stores Mini IOS / Subset of IOS.
Stores ROM monitor program.
Flash: Stores IOS (Internetwork Operating System)
Boot Strap Program: Stores in ROM.
Bring up and load device.
Load Mini IOS.
Power On Self Test (POST):Stores in ROM. It Checks hardware are
functional. Checks Interfaces / Ports are present.
Mini IOS: Bring up interfaces / Ports. Load IOS from flash into RAM.
ROM Monitor: Stores in ROM. Used for manufacturing, testing and troubleshooting.
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Cisco IOS:
The original and widely used OS, supporting a broad range of hardware
and features. It's suitable for smaller to medium-sized networks and many
different.
Latest Version: 15.9(3)M11 / March 2025
Router series: 800/1800/1900/2800/2900/3800/3900/7600
Switches series: Catalyst 2960/3560/3750/4500/6500
Cisco IOS XE:
An evolution of IOS, offering a more modern architecture, improved
scalability, and better support for new technologies.
Latest Version: 16x and 17x
Engr_Asad Khan 8/4/2025
Router:
Aggregation Services Routers (ASR) 1000 series:
Integrated Services Routers (ISR) 4000 series
Cloud Services Routers (CSR) 1000v
Catalyst 8000V Edge Software
Catalyst 8200/8300 Series Edge Platforms
Switches:
Catalyst 3650/3850 Switches
Cisco IOS XR:
A high-end OS designed for large-scale, high-performance networks,
particularly service provider networks.
Latest version 24.4.2 March 2025
ASR 8000, 9000
NCS (Network Cloud System) 5000 Series:
Engr_Asad Khan 8/4/2025
Switch & Router Booting Process:
Step 1: First, the switch loads a power-on self-test (POST) program
stored in ROM. POST checks the CPU subsystem. It tests the CPU, DRAM,
and the portion of the flash device that makes up the flash file system.
Step 2: Next, the switch loads the boot loader software. The boot
loader is a small program stored in ROM and is run immediately after
POST successfully completes.
Step 3: The boot loader performs low-level CPU initialization. It
initializes the CPU registers that control where physical memory is
mapped, the quantity of memory, and memory speed.
Step 4: The boot loader initializes the flash file system on the system
board.
Step 5: Finally, the boot loader locates and loads a default IOS operating
system software image into memory and hands control of the switch over
to the IOS.
Engr_Asad Khan 8/4/2025
Next Lecture
Router & Switch Access Methods
Thanks
Engr_Asad Khan 8/4/2025
