6850E 6250 cisco 2960

[girgi]

Hello,
I have following problem:
I have network, you can see it on attached picture. I have core switches (2X6850E in stack), several 6250-p48 switches and 2 cisco 2960 switch. on core switches there are connected servers by double Gb port by Link aggregation.
on access switches (6250 and 2960) there are connected lot of devices. they are about 350 devices in one VLAN. this devices are IP cameras.

system was working without problems for a long time. One day problems begun, some times connection from server to cameras is losing for few secondes (1 - 5 seconds). I did not make any changes in system.

this connection lose is not simultaneously for all devices. also I run ping from server to camera. during hour 1% is lost.
there are no interface errors on switches.

what is strange, I mention on cisco switch, when I connecting some device on cisco switch, it starts logging "mac address flapping between interface fa0/1 and Gb0/1.".
where fa0/1 is interface which I am connecting device on cisco swich, and G0/1 is interface uplink to the core switch (6850E). I had this uplink 2xGb ethrnet in link aggrigation, but I change it and now I have only 1 connection. but this mac address flapping is every time when I'm connecting some device on cisco switch. after few line of this log warning massage, traffic is going from this new device without problem.
I checked every connection and there is not chance of loop.

CPU usage on all swiches OK. also interface usage % is not high, it is about from 2-10% depend on ports.

I do not understand what is problem of this 1% of ping request time out. and server to camera connection lost for few seconds.

[benny]

I assume you have an Spanning-Tree issue.

Please change the Cisco configuration to use "portfast" on all ports that don't face the core/uplink.
If this helps, I'll tell you why this happens.

B

[eseneres]

So what does setting Portfast on the Cisco side do to solve the packet loss problem?

[slixxboy]

Hi benny, if this scenario could not help to solve the issue, what is the best solution for this?

I have the same project (voice, data & camera) the core switch are OS6850E-U24X (2) and edge switch of OS6250 (22).

Please let me know your advice for this. Thanks

Victor