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New Member

VLAN with Catalyst 2960 S 10G - Packets not echoing on all ports

This is an initial attempt to try to describe and get some help on the topic above.

I will try to briefly describe the question on behalf of our program engineers. If my question is not clear enough, or does not make sense, please let me know and I will refine it with some help. Thanks.

We sometimes, not often, experience dropped packets with some of our 2960 switches. when that happens we use the fact that the switches echo or replicate the messages on all ports (multicast/broadcast) so we can verify whether the issue is with our HW or with the switch itself.

However, one of the switches does not echo messages on all ports (multicast)...

Is that a configuration matter?


Don J.


Is your problem with

Is your problem with multicast or are you dropping packets when pinging a single IP address (say pinging to  a single host should have nothing to do with multicast. 

Its is impossible to pin point where the drops are occurring, but in general you need to decrease possibilities, so ping from something close to the address your are trying to ping, so for instance from the switch itself. then move up the transition path and see when your drops start occurring.

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New Member



Both actually.

We are not using the switches in a real networking environment per se but as part of a special test equip rack to test some HW.

We are passing UDP packets thru the switch and sometimes observe dropped packets, and on some other rare occasions, dropped fragments within a packet, which is difficult to explain since all packet contents are ok before and after the dropped fragment (UDP headers and data are ok before and after)

And that's why we wanted to use the multicast feature of the switch to see if the switch dropped that single fragment on one port only or on all ports, or was it the HW under test that dropped the fragment and the switch just passing it along?