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hell_angelFlag for Malaysia

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Spanning Tree

hi guys...

recently deploy 2 Dell powerconnect M8024-K switch to customer environment with Cisco as core swtich.

Dell switches is connected with multiple uplinks to different core swicthes in different subnet.
Cisco core is using PVST and they are STP root.

UAT test scenario include port failover at different subnet. found some uplink port, when i did shutdown at the port, it either take more than 7 drops to failover and fail back.
some VLAN only has 1 fail over and back.

uplink port at cisco is not configured with portfast. i suspect this is due to STP learning. tried change cisco STP mode to Rapid-PVST and it doesn't help. end up i issue spanning-tree disable to fully stop the STP. and i can get 1 ping drop during failover and back.

is spanning-tree disable is ideal way to resolve this issue... ? any other option i should look into..? tried spanning-tree guard root. end with the uplink is blocked.

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dell default is RSTP. tested in lab with cisco switch.
with PVST - failback take about 6-7 ping drop from Windows
with R-PVST - 1-2 drops.
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Portfast actually means ignore STP, until a conflict actualy happens.. [ i.e. you will get a broadcast storm first] and then portfast will be removed. To have Rapid PVST work you need it on both ends of a link, otherwise the core [ Your cisco] will still use polling with the long timeout.  Cisco should know how to deal with Rapid PVST.