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IO memory

This is partial output of show version

cisco 2620 (MPC860) processor (revision 0x102) with 53248K/12288K bytes of memory.

the router has 64 mb ram.

is the 53 mb / 12 mb division for processor/ io memory ???

Isnt this value for io memory (12 mb)??

If yes, does the value of this memory allocated, be changed using

"memory-size iomem" command...??

Is it advisable to reduce/increase this value ??? I have seen some 2600s allocating just 4 mb for memory, some 6, some 8 etc....on what basis, does the router allocate the memory size for IO....

On a production router, what is the impact of this command, if we reduce the memory say...from 12mb to 8mb......Should I put a maintenance downtime window, for test this ??



Re: IO memory

the 53 mb is the main memory and the 12 mb is shared

you can change the io mem size by using the 'memory-size iomem xx' command I beleive the default allocation is 75/25 %


Re: IO memory

one more thing changing the io mem requires a reload

Re: IO memory

Ok, the shared memory is used for storing packets to be routed.

If i change iomem size using above command, will the shared memory size change ???


Re: IO memory

yes , You change it to the percentage of total memory you want allocated to shared memory. For example if ou want to allocate 10 % of total memory for shared you use the command 'memory-size iomem 10'

use the sho mem command this will show you the lowest the shared memory ever went. This can give you a good idea of what is a safe percentage to use.

Re: IO memory

I see the following when i give show mem.

Total of 33 mb for processor and 12 mb for IO are shown of which,

4.3 mb is used in processor mem and 1.8 mem in IO mem.

So free mem left is around 28-29 mb for processor mem and around 10 mb for IO mem.

I have got 64 mb of RAM and where is the rest of the RAM going ??

64 - (33+12) = 9 mb ??


Re: IO memory

to hold the image in Ram

Re: IO memory

Hmm.....didnt think abt that part.

Thanks for the replies...Cheers!