Information Technology Reference
In-Depth Information
CPU use is verified by the show process or show process cpu commands, as shown in Example
3-2. Both of these commands provide a list of the router's CPU use in the last five seconds, one
minute, and five minutes. The show process cpu command also shows the processes.
CPU Use Verified
Example 3-2
R2#show process
CPU utilization for five seconds: 16%/14%; one minute: 17%; five minutes: 16%
PID QTy PC Runtime (ms) Invoked uSecs Stacks TTY Process
1 Csp 25F66C 0 171 0 2640/3000 0 Load Meter
2 M* 0 3000 336 892810072/12000 0 Exec
3 Lst 24880C 20694 1083 19108 5740/6000 0 Check heaps
4 Cwe 23FC10 4 1 4000 5604/6000 0 Chunk Manager
...
...
R2#sh process cpu
CPU utilization for five seconds: 21%/14%; one minute: 18%; five minutes: 16%
PID Runtime(ms) Invoked uSecs 5Sec 1Min 5Min TTY Process
1 0 163 0 0.00% 0.00% 0.00% 0 Load Meter
2 2908 311 9350 0.00% 1.58% 0.57% 0 Exec
3 20357 1064 19132 6.47% 1.71% 1.83% 0 Check heaps
4 4 1 4000 0.00% 0.00% 0.00% 0 Chunk Manager
...
...
5Sec 1Min 5Min
Primary Memory
Primary memory is also referred to as main memory. DRAM chipsets store primary memory.
DRAM is volatile, which means that if the router is turned off, all contents stored in system
DRAM are erased. Primary memory stores data, such as routing tables, Address Resolution
Protocol (ARP) caches, and operating code (in most models). Many IOS functions, such as
OSPF, use a lot of memory, and you need to make sure that you have enough memory or the
router might crash. With over 118,000 BGP routes so far, routers connected to the Internet
require 256 megabytes or more of RAM. Different code versions and feature sets require
different amounts of system RAM.
Nonvolatile RAM (NVRAM)
NVRAM stores the router configuration files. NVRAM is nonvolatile because it does not lose
its contents when powered off, which makes it analogous to a floppy disk on a PC. Because
NVRAM stores a text configuration file, it is approximately 256 KB in size.
Read-Only Memory (ROM)
Some routers might have a ROM chip that contains a version of the IOS that supports minimum
functionality. The ROM chip also contains the power-on diagnostics and ROM monitor pro-
gram. The only way to upgrade the code in the ROM is by replacing the ROM chip.
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