文档介绍:Routing and Routers Routing and Routers ? Router Basics ? Router Startup procedure ? Routing ? Router configuration Router Basics ponents RAM NVRAM Flash ROM Interfaces Console Auxiliary RAM ? Temporary storage for router configuration files ? RAM content is lost on power down or restart ? Stores... ? Routing tables ? ARP cache ? Fast switching cache ? Packet buffering ? Packet hold queues NVRAM ? Non-volatile RAM ? Stores backup/startup configuration files ? Content is not lost when router is powered down or restarted. Flash ? EEPROM (Electronically Erasable Programmable Read-Only Memory) ? Holds the Cisco IOS ( Operating System) ? Allows updating of software without replacing the Flash chip ? Multiple versions of IOS can be stored ? Retained on power down ROM ? Contains POST (Power On Self Test) ? A bootstrap program (loads the Cisco IOS) ? And operating system software ? Backup, trimmed down version of the IOS ? Upgrades require installing new chip set Interfaces ? Network connections through which packets enter and exit the router ? Attached to the motherboard or as separate modules. Router Startup Procedure