Traffic Drops on Management Interface VLAN

[sdavis6806]

I have over a dozen SG200 switches all with the same issue. Out of nowhere we started getting drops on all of their management interfaces for a certain VLAN.

The following is the ping results to one of the switches management interface:

Packets: Sent = 870, Received = 789, Lost = 81 (9% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 10ms, Average = 1ms

When I change the management VLAN and IP address it resolves the issue.

Connections for other clients on the same VLAN has no drops or network issues and pings to the VLAN gateway report no loss.

What next?

[sdavis6806 · Accepted solution]

I found the issue.

I noticed that if I didn’t have VLAN1 associated with any ports on a switch then the management interface would not drop packets.

BTW this environment was built before I got here which is the reason VLAN1 is still being used. If it was up to me there would be nothing configured on VLAN1 but I digress.

Building on my discovery I found that the management interface had an IPv6 address associated to it. After deleting the address the drop issue stopped.

[MikeyP]

I did some further investigation and eventually opened a TAC case, the issue was there is a software bug in version 3.9.1E that can cause the floodset to stop forwarding if there isn't enough traffic being passed, upgrading to 3.9.2E or later resolved the issue, I went ahead and migrated my equipment to 3.10.0E.

[joeisbell]

What do you mean by "Floodset to stop forwarding"?

I am not familiar with the term "floodset" but I believe I am experiencing the same issue and will try upgrading from 3.9.1 to something else.

Thanks,

Joe

[MikeyP]

I forget the command to show the floodset but it's a software bug that occurs when there isn't enough traffic on a single vlan, it's more likely to occur on a management vlan because there isn't much traffic passing but it could mess up your data/voice vlan if they fall into the same situation.  The fix is to update the OS version, shut no shut the interfaces that are not forwarding traffic on that vlan or ping the IP from the device which will force the traffic to start.