Talk:Spanning Tree Protocol

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Explicit definition of "Segments"[edit]

I think it might be useful to add a description of what "segments" on an ethernet network are. Nowadays, I think of things in terms of fully switched networks - whereas a network "segment" is a shared medium (thin ethernet over coax; twisted pair on an old hub) with many nodes and bridges on it. If you do not have a good understanding of this concept it's hard to grok the point of Designated ports.

Hmm, do dumb switches forward spanning-tree frames? If so, I guess a dumb switch would be considered a segment in this context.

If a bit about dumb switches is added, it would be prudent to add a note of caution. I've definitely seen cases where a dumb switch, or perhaps an intelligent switch that had STP disabled, has caused a broadcast storm when dually linked to a LAN running STP. User:Danpritts —Preceding undated comment added 19:50, 8 May 2013 (UTC)

RSTP as it's own[edit]

I am reading a paper and didn't know what RSTP was, so I fed it into wikipedia search. Luckily, there is only 1 "RSTP" acronym so far as the "RSTP" page points here as well. RSTP had a 100% hit while Rapid Spanning Tree Protocol came in 2nd at 2.9%. I found my answer right there in the search results and immediately knew "oh, that's what RSTP" stands for. If it was hidden away in the Spanning Tree Protocol page... I don't think I would have found it as easily! ("Spanning Tree" has a 1.1% search result). I vote to keep the separate page and not merge, it is good to be categorized in "Network protocols" though. --BrianWiese 19:28, 20 March 2006 (UTC)

I also think this should be merged with STP

remark by User:Jishnua
please sign your comment, makes discussion easier ;-)
In the current state, the articles could be merged... However, i had the idea to extend the RSTP en MSTP articles some day (or hoping someone else would do it). RSTP and MSTP are compatible and extensions of STP indeed, some parts of the text on protocol operations would be the same, or refer to the other article; however, an more extended description of the RSTP en MSTP protocol operation and properties would make de STP article lengthy, and maybe it IS usefull to have some "stand alone" description of the protocols. --LimoWreck 00:48, 14 December 2005 (UTC)

I agree! Sergio

Yes, Do it!!

Yeah, I had no idea what is was...please add it, it fits well. Harry Cavallero

Merge Them

Most people will be looking for information on Spanning Tree, without realizing that in most network RSTP is the default version of spanning tree that is used. Both MSTP and RSPT should be merged into this article as the concept are very similar, and are evolutions on the basic STP protocol. By merging them together the reader will have the benefit of not only understanding the RSTP protocol, but the foundation of the protocol, and all related issues to do with it.

Sal Veya

Don't merge them - the mian article can explian the progression and the individual articles can provide more detail. Everyone is capable of clicking on the other pages. 14:27, 19 October 2006 (UTC)

The RSTP page IMHO is so short and mostly people will be looking for STP so I think they should be merged and if someday the RSTP section becomes so huge that it deserves individual article, people will call for that --krampo 14:00, 3 November 2006 (UTC)

Don't merge them, please. Like another user above, I came here looking for RSTP specifically, & I wasn't even sure of its expansion. I think it deserves a page of its own. --Arungoodboy 05:42, 5 December 2006 (UTC)

Algorhymes rock![edit]

Please add more specifications like this. Very nice. =) STP was designed to monitor and control the Layer2 Network, it has different variations like RSTP,MSTP and PVST+.

yes for my career prospectus, please add RSTP, MSTP

yet another vote - merge the 3.

bad choices[edit]

do real spanning tree implementations have stuff built in to prevent bad choices (e.g. using a 100 megabit link that some luser connected by plugging a patch cable between two wallports when a gigabit one is availible) or to prevent massive performance changes if a dead switch is replaced? Plugwash 17:31, 29 April 2006 (UTC)

I was loking for STP concerning Layer 2 and was not aware of something like Rapid STP. The search brought me sraight to RSTP which proved to be an enlightenment and motivation to further learn the subject. (talk) 19:22, 26 July 2008 (UTC)yash Pal Jagia

More instructive and specific than loop-free 2 words alternating or augmenting, if you like call method path with no cycles —Preceding unsigned comment added by Implements (talkcontribs) 14:14, 13 June 2010 (UTC)

Problems in Article[edit]

In the opening paragraph of the article there is a sentence that doesn't make sense to me. However, I don't know enough about the topic to really correct it, so I'm hoping that by noting it here, somebody else can make the fix. The part I'm confused by is:

First, there would be a broadcast storm caused by broadcast packets looping. Second, the traditional source-based location system used by switches to operate correctly. The result of this would be to cripple the network.

The middle sentence is incomplete; it seems to be missing something. It's just a dangling subject, without an action. Anyone want to clue me in? If someone can give me the technical info I'll rewrite it, but I don't understand STP well enough to know what's being meant here. --Kadin2048 21:37, 1 November 2006 (UTC)

  • The reference to broadcast storms in the article is arguably incorrect. The LAN is flooded as a result of bridge loops, but a "broadcast storm" is defined by IETF and Cisco as network flooding as a result of an incorrect broadcast packet. So mentioning it here suggests that the problem is more restrictive than it is, i.e., if you avoid broadcasting you won't have the problem. But that's not the case - the flooding occurs whether you have broadcasting or not. The incorrectness of the mac-address-table will also occur, but since that's a problem internal to the bridges and not likely to be understandable to a lay reader without considerable explanation, I think the introduction should restrict itself to flooding as the big problem with bridge loops. Ngriffeth (talk) 15:29, 11 April 2008 (UTC)

The Poem[edit]

Is it just me, or do the links mess up the poem? I know wikifying stuff is the way, it just seems so out of place in the poem. Nichlas 15:13, 16 January 2007 (UTC)


Since all of the articles discuss a form of the STP algorithm, they should be merged under one twiki page.

User: ftmkx


It was stated that STP was from the 802.1w conference while RSTP was from the 802.1d conference. This is actually backwards. RSTP is 802.1w and STP 802.1d. Check for yourself, Cisco Press CCNA ICND book for the 640-811 exam. pg. 36.

No idea what you're blabbering about. Don't polute this talk page with irrelevant nonsense.
He's correct, your polluting by posting about a subject you don't know about —The preceding unsigned comment was added by Charfles (talkcontribs) 06:14, 9 February 2007 (UTC).

There seems to be part of the text duplicated in the first paragraph: "The spanning tree network protocol provides a loop free topology for any bridged LAN. The Spanning Tree Protocol, which is also referred to as STP, is defined in the IEEE Standard 802.1D. [...] STP is used in switched networks to prevent loops, and has been standardized by IEEE 802.1D. " The last sentence is already completely included in the first two. Could it be removed ? MJost 14:31, 12 December 2006 (UTC)

Has been done already. Mauro Cicognini 12:42, 12 July 2007 (UTC)

Merge (BPDU)[edit]

I recommend that the BPDU article be merged into the BPDU section of this article. Any thoughts on this? 01:08, 11 May 2007 (UTC)

The other option is to create a separate page for BPDU - have a one liner on BPDU here and reference that. am dealing with this issue right now on some of the Ethernet articles, however. What size is too big? this article is pretty big. and How do you keep people from rewriting the BPDU article? Sorry I cant help with much opinion, but more questions--Boscobiscotti 06:27, 12 May 2007 (UTC)
Second thought - It should be merged. integral to understanding--Boscobiscotti 19:24, 12 May 2007 (UTC)
It should be merged and redirected. It is thrown out of context in a standalone article. Kremso 06:47, 21 May 2007 (UTC)

I think that the BPDU article should be moved into the BPDU secion of the STP article due to the importance that BPDU's have in the Spanning Tree process. It is an integral part and having it in the STP article would be very beneficial.

(New comment, the above is anon) Definitely merge, BPDU's don't exist outside of STP and as already mentioned are integral in the protocol. Ngriffeth 14:43, 3 July 2007 (UTC)

Let's just go ahead and merge it, and provide a redirect on the old BPDU page... Mauro Cicognini 12:43, 12 July 2007 (UTC) ... done. Mauro Cicognini 13:09, 12 July 2007 (UTC)

Explaining paragraph move from end of introduction to "evolution"[edit]

I moved the mention of DEC STP and interworking issues down to the evolution section; also added references to the standards documents and to one of the Cisco manuals that explains a problem with interworking of DEC and IEEE STP. Ngriffeth 17:25, 12 September 2007 (UTC)

Removed poetical section - non encyclopic?[edit]

I removed an entire section from the article because it seems to me to be non-encyclopedic. Here is the original text for archival purposes:


Radia Perlman, the inventor of the algorithm, summarized it in a poem titled "Algorhyme"
(adapted from "Trees", by Joyce Kilmer):

I think that I shall never see
A graph more lovely than a tree.
A tree whose crucial property
Is loop-free connectivity.
A tree which must be sure to span
So packets can reach every LAN.
First the Root must be selected
By ID it is elected.
Least cost paths from Root are traced
In the tree these paths are placed.
A mesh is made by folks like me
Then bridges find a spanning tree.

You can listen to the author of STP playing on piano and her daughter Dawn Perlner (voice) performing at MIT's Lincoln Laboratory, a musical version of the poem, set by the author's son Ray Perlner, which can be downloaded from NetworkWorld Podcasts Section[1].


Triddle 00:38, 29 September 2007 (UTC)


There is no mention of Cisco's PortFast STP optimization in this article or elsewhere on Wikipedia. My understanding is that when enabled, PortFast puts a port into forwarding mode immediately after link is established. This gives end stations immediate connectivity at the expense of the possibility of a brief storm if the connection results in a loop. I believe the PortFast option was incorporated into the RSTP enhancement but I need someone to verify this before editing the article. Meanwhile, I've removed recent edit claiming that Blocking is the initial state for STP. While the statement is true for the original 802.1D, it needs some qualification given the above. --Kvng (talk) 13:31, 25 August 2008 (UTC)

Not an OSI protocol[edit]

The first sentence is highly misleading as STP is not an OSI protocol at all. I suggest to reword it to reflect that if described by the OSI model then STP falls into the data link layer. --Pgallert (talk) 10:23, 6 February 2009 (UTC)

Agree ; I've removed the reference to the data link layer as dubiously helpful. Skandha101 • 19:47, 29 July 2011 (UTC)

Brocade PVST and Cisco PVST[edit]

I've removed a clause saying that Brocade supports PVST. It is probably untrue that all Brocade products support PVST, but more importantly, I cannot confirm that the Brocade PVST is the same as the proprietary PVST described in the wikipedia article, or that it interoperates with Cisco. The source listed says nothing about Cisco.

 Original line: Both PVST and PVST+ protocols are Cisco proprietary protocols and they cannot be used on most 3rd party switches, 
 although Brocade supports PVST[1] 

Skandha101 • 19:42, 29 July 2011 (UTC)

Actually, Brocade (Foundry) switches support PVST+ and interoperate with PVST. Per the "Brocade MLX Series and NetIron Family Configuration Guide, r05.2.00b"...

PVST or PVST+ compatibility
Brocade’s support for Cisco’s Per VLAN Spanning Tree plus (PVST+) allows the Brocade device to run multiple spanning trees (MSTP) while also interoperating with IEEE 802.1Q devices1. Ports automatically detect PVST+ BPDUs and enable support for the BPDUs once detected. When it is configured for MSTP, the Brocade device can interoperate with PVST.

Overview of PVST and PVST+
Per VLAN Spanning Tree (PVST) is a Cisco proprietary protocol that allows a Cisco device to have multiple spanning trees. The Cisco device can interoperate with spanning trees on other PVST devices but cannot interoperate with IEEE 802.1Q devices. An IEEE 802.1Q device has all its ports running a single spanning tree. PVST+ is an extension of PVST that allows a Cisco device to also interoperate with devices that are running a single spanning tree (IEEE 802.1Q). The PVST+ support allows the Brocade device to interoperate with PVST spanning trees and the IEEE 802.1Q spanning tree at the same time.

Similar language appears in the "FastIron Configuration Guide, 07.3.00"

Hank Massey (BCNE, CCNA) — Preceding unsigned comment added by Hjmassey (talkcontribs) 22:28, 24 January 2012 (UTC)

STP Port Status Times[edit]

It doesn't mention that the time each port stays in each status for. Blocking 20sec, Listening 15sec, Learning 20sec. 09:46, 15 May 2014 (UTC) — Preceding unsigned comment added by (talk)

SSTP: Single Spanning Tree Protocol[edit]

My new Brocade switches support something called Single Spanning Tree Protocol. I don't see any information about that here.
It appears to break links on our Cisco Catalyst 6500 router whenever it detects a new device.

Yakatz (talk) 00:40, 11 June 2015 (UTC)

  1. ^ "Brocade BigIron RX Series". Brocade. Retrieved 23 June 2011.