SNMP on a 4507

[Lee Cobley]

Hi everyone,

I have a question about a Cat 4507 and SNMP.

The company I work for request that the snmp status is sent back the the network monitoring software once a second. ( they are keen on this). but I cant get the 4507 to send back info fast enough. I get a responce from the switch once every 4ish seconds. see below

2013.May.30 09:11:40	0
2013.May.30 09:11:39	282344
2013.May.30 09:11:38	0
2013.May.30 09:11:37	0
2013.May.30 09:11:36	520056
2013.May.30 09:11:35	0

Does anyone have any idea how to get the switch to respond faster?

Thanks for any help

[Marvin Rhoads]

What comprises "SNMP status"  in your situation?

I see a couple of potential issues with a once/second periodicity of SNMP polling:

a. some large SNMP gets or MIB walks take several seconds to process. So you never finish the first one before requesting the second (and third, etc.)

b. SNMP is a low priority thread on the device and if it is busy actually switching network traffic it will respond to SNMP requests more slowly.

If you want more affirmative awareness of issues on the devices I'd think that SNMP traps and syslogging would be more effective. You could also do a simple ping at that once/second rate (thought I'd submit that's still overkill).

[Lee Cobley]

Hi Marvin and thanks for the relpy,

They would like the bandwidth monitoring on the up link to be every second. The idea is to hopefuly catch microbursts on the line.

[Marvin Rhoads]

SNMP isn't designed to be a real time tool and query every second.

I'd push back on the requirements and suggest something like Netflow and/or span ports or NAM depending on the overall system design. What's the operational model / process that's going to take action on something based on getting it in one second vs. five seconds?

[Lee Cobley]

Hi Marvin

Thanks again, I agree and have tried to explain that SNMP is not designed for this, but the problem lies in that we have 3750 switches in the network that do respond every second and send back the information on the bandwidth, and the management feel the 4507 should do the same.

The reason they are very keen on every second is that they dont want to miss any short bursts in the bandwidth and can analyse the flow and see any microbursts. I have suggested Polling every 5 seconds but they insist they will miss vital information between checks.

[Marvin Rhoads]

FWIW in 25+ years working with Cisco gear I've never seen anyone setup SNMP polling at once/second. It's just not the right tool for that.

That aside, it sounds like the customer is dead set on it despite it being against both best practice and common sense. In that event perhaps you can sell them on upgrading their supervisors. You didn't mention what supervisor they are running but I'd suspect a Sup 7 or such might have the additional horsepower required to crank out SNMP responses more quickly.

Note that's just a projection - it would have to be labbed up to verify.

[Lee Cobley]

Hi Thanks for the help. They are all nice and new 

Supervisor 7L-E

I will try to figure something out.