I was reading a wiki page about Spanning Tree and the following quote intrigued me: "Both PVST and PVST+ protocols are Cisco proprietary protocols, and few switches from other vendors support them. "

As far as I know, Cisco is proprietary about Spanning-Tree features: Port Fast, BPDU Guard . . .

That's my question, I have no sure about it, I would like to confirm my statement.


Many Cisco protocols are proprietary simply because Cisco created a protocol to facilitate something where there wasn't an industry standard. For instance, Cisco created HSRP, and, eventually, submitted it for RFC approval. The industry feared extending the influence that Cisco has over networking, and it created a competing protocol, VRRP, which really does the same thing that HSRP does.

Cisco didn't change the Spanning Tree Protocol, but they extended it so that each VLAN can have a separate Spanning Tree instance (PVST: per-VLAN spanning tree). The industry created Multiple-instance Spanning Tree, but MSTP doesn't go as far as Cisco's PVST does. As rapid spanning tree became a standard, Cisco extended PVST to use Rapid Spanning Tree on a per VLAN basis (Rapid PVST).

  • I searched on the list of Cisco's Protocols but I didn't find. Thanks Ron! Do you know which are these "few switches from other vendors"?
    – TMoraes
    Oct 23 '15 at 21:09
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    Both HP and Dell, at one time or another, had switches for servers which followed Cisco standards. Huawei originally stole Cisco code (a charge it disputes, but one where a court sided with Cisco), so it had products which completely mimicked Cisco features. I don't know of any particular list, and I certainly don't know, or can't remember, all the products which have used Cisco features. By the way, not everything in your question is actually a protocol. Portfast, BPDU guard, etc. are features which a switch uses, but there is no communication involved, so they aren't really protocols.
    – Ron Maupin
    Oct 23 '15 at 21:17
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    Also, the key difference between PVST and MST: MST allows the admin to map VLANs to a select instance (or the common instance); this allows for "load spreading" of redundant paths, but does make for complex configs. Most implementations of MST limit the number of instances. (eg. 6, 8, 12, 16, etc.)
    – Ricky
    Oct 23 '15 at 21:49
  • @RickyBeam, yes. The thinking one of the vendors who sponsored MST told me that PVST puts too much of a strain on switches, so MST is a better solution because it limits the number of STP instances. They both have adherents and use cases.
    – Ron Maupin
    Oct 23 '15 at 21:52
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    I just wanted to add that Cisco is not the only vendor to implement proprietary technology or versions of standards. For example, Extreme has (IIRC) "Extreme Multiple Instance Spanning Tree Protocol". As a side note, Extreme is also one of the vendors that can work in a PVST/PVST+ configuration as well.
    – YLearn
    Oct 23 '15 at 23:09

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