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08-16-2012 08:22 PM - edited 03-07-2019 08:23 AM
Hi everybody.
I was doing lab where two switches were connected over trunk. When i capture the traffic on the trunk, i found both stp and pvst+ traffic passing over the trunk. The switches were at their default setting.
My question is why are cisco switches running both stp/pvst+ at the same time? I understand the role this protocol perform but why do we both i.e stp/pvst+?
thanks and have a great day.
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08-21-2012 07:16 PM
Hello Sarah,
The reason to run classic STP even between PVST+ switches is twofold: assuming that their interconnection may be through a shared medium (hub, WiFi, non-STP switch), to allow a STP-only switch to be connected and immediately start participating in STP at some point in the future, and to allow for native VLAN mismatch detection. Regarding the second point, you may be interested in reading the following document:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml
Best regards,
Peter
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08-21-2012 07:16 PM
Hello Sarah,
The reason to run classic STP even between PVST+ switches is twofold: assuming that their interconnection may be through a shared medium (hub, WiFi, non-STP switch), to allow a STP-only switch to be connected and immediately start participating in STP at some point in the future, and to allow for native VLAN mismatch detection. Regarding the second point, you may be interested in reading the following document:
http://www.cisco.com/en/US/tech/tk389/tk621/technologies_tech_note09186a00801d11a0.shtml
Best regards,
Peter
