Routing
Identify a router as a computer with specialised hardware and operating system designed for routing Give a router a basic configuration including IP addresses Routing tables Router activities – finding the best paths and switching packets
Connect networks together Find best routes Switch packets from one network to another Do this efficiently 24/7 Provide security by permitting or denying specified types of packet Provide quality of service by prioritising packets
CPU: control unit handles instructions, ALU for calculations RAM: volatile working storage ROM: permanent storage for POST and startup instructions Operating System: software that runs the computer System bus, Power supply
Long term storage is Flash and NVRAM, not hard disk Range of different interfaces all on different networks No input/output peripherals. Connect via a console PC and use PC’s keyboard and screen
Dynamic random access memory: as in a PC Temporary memory while the router is on Loses content when the router loses power or is restarted Holds running configuration Holds routing tables Holds ARP cache Holds fast-switching cache etc.
Non-volatile RAM: keeps its contents when the router is off Stores the startup configuration file When you have configured a router, you must save your configuration to NVRAM if you want to keep it
Electronically erasable, programmable ROM (EEPROM) Keeps its contents when the router is off Holds the operating system image (IOS) Allows the IOS to be updated Can store multiple versions of IOS software if it has enough capacity Can be upgraded by adding SIMMs
Permanent memory: cannot be upgraded without replacing the chip Holds power-on self test (POST) instructions Stores bootstrap program Stores ROM monitor software (for emergency download of IOS, for password recovery) May store basic IOS
Identify a router as a computer with specialised hardware and operating system designed for routing Give a router a basic configuration including IP addresses Routing tables Router activities – finding the best paths and switching packets
Connect networks together Find best routes Switch packets from one network to another Do this efficiently 24/7 Provide security by permitting or denying specified types of packet Provide quality of service by prioritising packets
CPU: control unit handles instructions, ALU for calculations RAM: volatile working storage ROM: permanent storage for POST and startup instructions Operating System: software that runs the computer System bus, Power supply
Long term storage is Flash and NVRAM, not hard disk Range of different interfaces all on different networks No input/output peripherals. Connect via a console PC and use PC’s keyboard and screen
Dynamic random access memory: as in a PC Temporary memory while the router is on Loses content when the router loses power or is restarted Holds running configuration Holds routing tables Holds ARP cache Holds fast-switching cache etc.
Non-volatile RAM: keeps its contents when the router is off Stores the startup configuration file When you have configured a router, you must save your configuration to NVRAM if you want to keep it
Electronically erasable, programmable ROM (EEPROM) Keeps its contents when the router is off Holds the operating system image (IOS) Allows the IOS to be updated Can store multiple versions of IOS software if it has enough capacity Can be upgraded by adding SIMMs
Permanent memory: cannot be upgraded without replacing the chip Holds power-on self test (POST) instructions Stores bootstrap program Stores ROM monitor software (for emergency download of IOS, for password recovery) May store basic IOS