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New Member

Several spanning tree instances in a single network

Hi there,

I have a new network with one Catalyst 4506, several 3Com Bay Gigabit Ethernet switches and Bay 450T swtiches. The over network network is configured as a star topology with the Catalyst 4506 as the hub and those 3Com Gigabit Ethernet switches as spoke. Those Bay 450T switches are connected to 3Com switches. I am afraid that there may be several spanning tree instances in this network which cannot be compatible with each other. May I ask what is the best way to config this new network? Disable spanning tree in Cisco device? Disable spanning tree in all those non Cisco devices? Or Treat each spoke as different layer 3 subnets? Pls give some advice on it.

many thanks


New Member

Re: Several spanning tree instances in a single network

hi there,

Disabling STP will not be a good move, cisco & 3com

Supports two type stp. Cisco will use PVSTP (Proprietary cisco) & CSTP(IEEE).3COM will use STP (IEEE) & Rapid STP (IEEE) well i dont know about Bay 450T.

so you can configure cisco boxes to run CSTP and 3com to run normal STP, that should solve the compatibility issue between Cisco and 3COM. I am sure Bay 405T will have their IEEE version of stp.

that may solve your problem

With regards


New Member

Re: Several spanning tree instances in a single network

Hi David,

I do not recommend disabling spanning-tree. This makes it much more complex to manage and troubleshoot. By default, the 4506 runs IEEE 802.1D spanning tree. If all devices are compliant, then there should not be a problem.

Dependent on the supervisor model (Sup3 or Sup4), it runs IOS and each port can be configured as a routed port. If permissible and would make you feel more comfortable, go with that option and have the 4506 as the hub to route the traffic. There should not be a penalty hit as it is done in HW.

L3 Interface Configuration,