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10 Cards in this Set
- Front
- Back
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Router Function |
Connect networks together Find best routes Switch packets from one network to another Provide security by permitting or denying specified types of packet Provide quality of service by prioritizing packets |
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Router as a computer |
CPU: control unit handles instructions, ALU for calculation
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RAM |
Dynamic random access memory: as in a PC Temp. memory while the router is on Loses content when the router loses power or is restarted Holds running config Holds router tables Holds ARP cache Holds fast-switching cache etc |
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NVRAM |
Keeps it contents when the router is off Stores the startup config file When you have configured as router, you must save your configuration to NVRAM if you want to keep it |
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FLASH |
Electronically erasable, programmable ROM (EEPROM) Keeps its contents when the router is off Allows the IOS to be updated Can store multiple versions of IOS software if it has enough capacity
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ROM |
Permanent memory: cannot be upgraded without replacing the chip Holds power-on self test (POST) instructions
Stores ROM monitor software (for emerg. DL of IOS, for password recovery) May store basic IOS for emerg. use (less common than it was) |
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Interfaces |
Can be attached directly to the motherboard Can be on removable and interchangeable modules Modules for different serial connections |
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Operating System |
As specialized computers, routers and switches need operating systems Cisco devices use the Cisco internetwork Operating System (IOS) There are versions for different models of router and switch, and different feature sets The IOS can be upgraded periodically |
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Naming IOS image files |
Platform-features-format-version
C2600 is the platform: Cisco 2600 series router I is a code for the set of features in this IOS, another is ipbase mz is a code to say that the IOS runs in RAM and the file is zip compressed 122-8.T5 is the upgrade version |
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Routing Table Principles |
1. Every router makes its decision alone, based on the information it has in its own routing table 2. The fact that one router has certain information in its routing table does not mean that other routers have the same information 3. Routing information about a path from one network to another does not provide routing information about the reverse, or return, path. |
