Inconsistant Ping Times Between Vlans - Catalyst 3750.

Unanswered Question

I have a number of locations exhibiting this behavior.  Here is the typical layout:

Cisco 3750 PoE running 12.2.44(SE6) IP Services.

Vlans Defined - 10,20,30,40,50,60,70,80,90

IP Routing Enabled

SDM Preferred Routing Enabled
Low Traffic Volume - Typically 10 users or less.

Typical CPU Usage - 4% to 9%

Using a constant Ping, we see response times between devices on the same Vlan at less than 1ms with the occasional spike.  Expected behavior.

But between devices on seperate Vlans, we typically see this - 1ms, 15ms, 1ms, 15ms, 1ms, 15ms, 1ms, 15ms....

The problem seems consistent regardless of which Vlan is the source or destination.

Even when sourcing Pings from the Switch itself we see times such as  -  round-trip min/avg/max = 1/2/9 ms.  The MAX time is high when compared to one of our sites using a Catalyst 3550 with IP Routing Enabled.

At our 3550 sites (Running Same IOS), we see  -  round-trip min/avg/max = 1/2/3 ms or less.

For our comparison test, the 3550 site was a high traffic volume site, yet the Ping responses are normal (i.e., expected behavior)

Any idea why we are seeing these odd Ping Times between Vlans on our 3750's?

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Ganesh Hariharan Tue, 12/01/2009 - 22:18
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what is the responce when u ping server in the same vlan


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