2960X output drops with 6900 series phones

Robin Burns · ‎08-16-2018

After reading several similar threads I'd like to start a new one. We are seeing increasing output drops on 2960X and 2960S ports in a specific circumstance: A port is connected to a 6961 or 6941, AND the phone is supporting a computer or other device via the phone's relay port. We don't see steady drops (typically none) when a phone is connected by itself, or when some other 10Mb or 100Mb device is connected to the switchport and auto-negotiates a slower speed.

We don't see this problem on 3560's, 3750's, or 3850's. Only 2960S and X models.

Last week I upgraded a 2960X to the latest starred version, 15.2(2)E8, but that had no effect on the situation described above.

Anyone else encountered this problem with 6900 phones and 2960's?

Leo Laohoo · ‎08-16-2018

@Robin Burns wrote:

A port is connected to a 6961 or 6941, AND the phone is supporting a computer or other device via the phone's relay port. We don't see steady drops (typically none) when a phone is connected by itself, or when some other 10Mb or 100Mb device is connected to the switchport and auto-negotiates a slower speed.

This tells me the phone is not the problem but the PC. Is QoS enabled on the port or not?

@Robin Burns wrote:

We don't see this problem on 3560's, 3750's, or 3850's. Only 2960S and X models.

Catalyst switches are known to have very shallow port buffers. The shallowest of them all are Catalyst 2K switches (they are, after all, the cheapest model) and the Catalyst 3K are slightly higher.