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Different STP Modes on same LAN

Hi There,

Are there any issues with switches on the same LAN running different spanning-tree modes? I have a LAN where some switches are running pvst (ieee mode) and some that are running rapid pvst.

Will the only issue be that the pvst switch ports will take longer to change states during a topology change?

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Hall of Fame Super Silver

Re: Different STP Modes on same LAN

Hello Tobin,

until some switches run PVST the STP convergence of your network will be that of 802.1D and not that of 802.1w.

Depending on your topology the difference can be less dramatic then expected:

if you have access switches dual homed to distribution using STP uplink fast, STP portfast on all user ports you should be fine.

Rapid STP falls back to STP on a per port basis when it detects an 802.1D peer.

Hope to help

Giuseppe

1 REPLY
Hall of Fame Super Silver

Re: Different STP Modes on same LAN

Hello Tobin,

until some switches run PVST the STP convergence of your network will be that of 802.1D and not that of 802.1w.

Depending on your topology the difference can be less dramatic then expected:

if you have access switches dual homed to distribution using STP uplink fast, STP portfast on all user ports you should be fine.

Rapid STP falls back to STP on a per port basis when it detects an 802.1D peer.

Hope to help

Giuseppe

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