High I/O memory utilization 2960

[accaaccahh]

We recently installed two 2960, both of them with this fw version:

Cisco IOS Software, C2960S Software (C2960S-UNIVERSALK9-M), Version 12.2(55)SE3, RELEASE SOFTWARE (fc1)

The switches see very few traffic (under 40MB on all interfaces, summed, so far), however, I/O memory ultilization is about 80% as can be seen from the show memory command:

                Head    Total(b)     Used(b)     Free(b)   Lowest(b)  Largest(b)

Processor    2B89A18    73969000    27198964    46770036    45060368    29367536

      I/O    6200000    14680064    12185292     2494772     2323116     2380896

Driver te    1A00000     1048576          44     1048532     1048532     1048532

The memory allocated is almost all Packet Data, by init, "sho memory io dead" returns  zero, the memory usage seems constant, there are no errors on the log, the switches operate correctly, no packet has ever been dropped, cpu usage is about 4%.

Here I showed info for one switch, the other is in the same situation.

I just want to know if this behaviour is expected, I don't want to find out problems when the switches will be in production whit real traffic.

[nkarpysh]

Hi David,

Packet Data should be seen under IO memory. SO smth else seems to be taking that from Processor pool. Can you please attach following commands to check:

- sh log

- sh ver

- show proc mem sorted

- sh mem sum

- sh memory io allocating-process totals

- sh memory io free

Nik

[accaaccahh]

Hi Nik, here http://pastebin.com/uRbrYXjV you can find the output of the command you requested.

Thanks for helping.

David

[nkarpysh]

Hi David,

I did some analysis and got on similar case analyzed by DE. While it is not documented, it was noted that this was by design and that it would not affect the switch as the switchport becomes more and more loaded.

Based on the configuration, the switch allocates dedicated memory to certain

processes / resources by default and then additional resources when the

configuration is added. This ensures proper functionality and is again by

design.

The I/O Memory pool buffers information transmitted to and from the CPU, and

does not affect the actual forwarding of packets on the switch.

I also checked this in our local lab with default configurations on the

switch. I saw that 83.4% of I/O pool was used with default config on the

switch.

Then I added some running config  and I observed 94.5% used.

SO this is how it works and I guess nothing to worry about.

Hope this helps.

Nik

[accaaccahh]

Nik

I'm glad everithing is ok with my switches, thank you so much for your replies, you have been of great help.

David

[nkarpysh]

Thanks David,

You can rate the post which helped for those to be helpful in future for others.

Thanks,

[waqas.arshad]

I would like to get your opinion on I/O memory utilization since we install the new chassis of Cisco 6880. It looks like we are at ~80% utilization. Is that within normal operating range?