Flash vs DRAM 1

[StephenWyker]

I have an 831 -- It has 12MB Flash and 16MB DRAM -- I know we need to upgrade one of the two to get the newest IOS ...

What do each one do? Where is the IOS and SDM stored? Can someone explain?

When I do the upgrade, when i remove the old SIMMs, do I lose all programming?

 

[JOAMON]

IOS is located on the flash so if new memory installed must reload IOS as there will be none on the new flash.
There are two ways to do this......

Xmodem the tried and true slow way....or...

tftp from rommon.....the fast way....

See the following sight....

http://www.cisco.com/en/US/products...figuration_guide_chapter09186a0080118d19.html

These commands are case sensative and must be in upper case....

 

[StephenWyker]

so if I upgrade the DRAM, no changes need to be made correct?

 

[jneiberger]

IOS is stored in flash but it runs from DRAM. When the router boots up, it loads the IOS from flash into DRAM. That allows you to upgrade the flash while the router is still running without causing an interruption. This was not true on older routers that ran from flash.

The flash just needs to be big enough to hold your IOS. DRAM needs to be able to hold the uncompressed version of IOS plus all the other stuff that you would expect (routing tables, etc.)

Software Advisor on CCO will tell you exactly how much DRAM and flash you need to run a particular image on a particular platform. Follow the recommendations.