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New Member

Router memory IO processor ?

HI All,

I was just curious as to how memory is allocated in a 2600 series.

I had this router that had 32/8 in sh vers.

When doing a sh mem summ

processor was 8 and i/o was 8 thats 16 in total.

I think by default I/O is 20%

What hapens with the 24mb of ram left,is this used for solely the system image ?the router is running j code Ip olny image is less that 3mb.

Also what uses I/O memory, routing table ??

The reason i ask is the router only had 52400b left of processor memory.Yet it had roughly 5,000,000 bytes left of I/O memory free it was only using around 35% of I/O.

After every 2weeks it would get to a stage were the router was still functioning though you could telnet to it as their obviosly wasnt any process memory left.I suspected memory leak but this router has been running for years..

The TAC said it wasnt a memory leak!

And suggested i allocate some of i/o to processor mem using memory i/o memory 30 command.

.If i applied the above command it would chamge I/O to 12mb and reduce processor mem to 4mb.

I didnt realise till reboot..And then the router was

destroyed (very ill)malloc errors and needed to be changed through romon>

when you apply the io memory command its calculating from the total memory "40" 20% of 40 is 8mb which is its default allocation from my analysis yet the memory I/Omemroy command effects only the processors memory allocated chunk.

What i needed to do was change I/O to 15 this would make I/O 6mb and processor 10mb which is what I was trying to achieve on tacs advice.

Can someone tell how the total 40mg of memory is allocated in this 2610 or other routers.

Also whats uses I/O mem

And the remaing 24mb what uses that its not wasted I take it ?




Re: Router memory IO processor ?

For 2600 router if sh ver output shows: 32/8 then your router has 8+32=40MB physical memory and %20 of this = 8MB is aloocated as I/O memory, rest (32MB) is used for processor memory. For 1600, 2600 and 3600, 7200 routers, DRAM is shared between processor and I/O memory and in the output of "sh ver" command X/Y says that X:portion of the physical DRAM allocated as processor memory and Y:other portion allocated as I/O memory, so total is sum of them. Processor memory stores IOS executable code, routing table and othr data structures required for IOS operation. I/O memory includes buffers of the routers interfaces. We can roughly say that I/O memory stores packets traversing the router. When you issue "sh mem sum" command total column of first line indicates total processor memory "after IOS is decompressed and builds its own data structures into the processor memory ". So you won't see 32M there. "Used" column of processor memory shows mem used by different processes (you can see with "sh proc mem" command) and "Free column will indicate free memory. ". I hope this and document below helps:


New Member

Re: Router memory IO processor ?

Ok thanks for the reply makes perfect sense now.

Links are good !

I think the technical expertise of TAC engineers has dropped a little lately.

I have no doubt Cisco has some of the most brilliant people in the industry.

The service is still A1 though technical expertise of the front line seems to have dropped.

The last two cases I have had I've been given wrong configuration changes that have required many more hours of down time.

The positive is I have gained more exposure to issues like these for which i'm gratefull.

Thanks again for taking the time to answer the questions.