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New Member

when to disable spanning tree?

Hi All,

Would it be safe to say that all ports connected to hosts should have STP disabled.

For the main reasons that:

1)      Every time a user turns off their PC spanning tree must be recalculated by all switches in that layer2 broadcast domain, this adds load on the network

2)      Some PCs may have issues getting an IP address as spanning tree will still be learning while the PC is requesting an IP (therefore dropping the PC Packet)

4 REPLIES
New Member

when to disable spanning tree?

Hi,

You can enable portfast in each interface in order to avoid this.

This will reduce the time for learning the MAC address.

Thanks

Vipin

Thanks and Regards, Vipin
New Member

when to disable spanning tree?

thanks heaps

Cisco Employee

when to disable spanning tree?

Hello,

I would avoid disabling STP on PC ports. As Vipin said - better to configure portfast t will transfer port to forwarding state immidiately) and other STP feature like BPDU guards, etc.

http://www.cisco.com/en/US/partner/tech/tk389/tk621/technologies_tech_note09186a008009482f.shtml

to make sure in case of bogus switch connected to this port - STP will still be stable.

http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst4000/7.4/configuration/guide/stp_enha.html#wp1019873

Hope this helps.

Nik

Cisco Employee

Re: when to disable spanning tree?

Hello,

I agree with both friends here. What you are talking about is well known, and the edge port type was specially created for these purposes: it does not generate topology changes when transitioning between up and down states, and becomes forwarding immediately after going up. In Cisco parlance, an edge port is called the PortFast port, and can be configured using the well known spanning-tree portfast interface-level command. Note that STP still runs on a PortFast-enabled port, just its behavior is modified. PortFast port still send BPDUs and are prepared to receive BPDUs, and should a BPDU be received, the port will lose its PortFast operational status and become a non-edge port until it is unplugged and plugged again.

In a switched network, it is almost never advisable to deactivate or disable STP.

Best regards,

Peter

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