Cisco SG300, SG500 , 2960X spanning tree none compatibility behavior.

[davidsonyo]

Hey folks,

I have a really strange issue with my 2960X switch that operates in PVST+ and that is connected to a Cisco SG300 and SG500 unit.

For some reason each device dose not recive any BPDU but they send it to each other.

Have tried set manually the root bridge priority to 4096 on the Cisco 2960X and on the other unity to higher but issue still exists.

All ports that is faces to each other are trunk ports there is native vlan configured on each. Cost and priority on ports are normal.

Problem is for some reason each switch individually thinks they are the "root bridge" since they do not receive any BPDU they only send it.

anyone familiar with this issue ?

Thanks in advance!

Dave.

[filopeter · Accepted solution]

Hello Dave,

SG300 and SG500 switches do not support PVST+. You have two choices, either migrate to MST (802.1s), or interconnect 2960X with SG300/500 switch using trunk and native vlan 1 (it must be 1). In the second case 2960X and SG300/500 stay STP compatible and will run 802.1D version on vlan 1.

Best Regards,

P.