Spanning Tree Portfast

Answered Question
Dec 4th, 2008

I have a 3560G that is the def gw for most of my net, as well as root of Spanning Tree. All my sites connect into this box via fiber, most of the main servers plug into this box, as well as Unity and CCM, etc.

Anyways, here is one port:

interface GigabitEthernet0/5

description Connection to PIX Firewall

spanning-tree portfast

Should I have portfast set on this port? Any harm by taking it off?

I have this problem too.
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Giuseppe Larosa Thu, 12/04/2008 - 06:54

Hello Doug,

spanning-tree is useful on user ports : that includes ports where router or firewall connects.

If the PIX is acting as a routed firewall it is not transparent you can keep it

STP portfast reduce the time to STP forwarding state knowing that no switch is connected on the port so it is useful on PCs and workstations to reduce time to up.

It also provide more STP stability: a change of state in a portfast port doesn't trigger a topology change notification

This avoids a useless STP recalculation.

Hope to help

Giuseppe

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