# Simple Loop Prevention Protocol

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{{Short description|Protocol developed by Nortel to protect against Layer 2 network loops}}
{{more citations needed|date=May 2019}}
'''Simple Loop Prevention Protocol''' ('''SLPP''') in [computer networking](/source/computer_networking) is a [data link layer](/source/data_link_layer) protocol developed by [Nortel](/source/Nortel) (previously acquired by [Avaya](/source/Avaya), now a part of [Extreme Networks](/source/Extreme_Networks)) to protect against Layer 2 network loops. SLPP uses a small hello packet to detect network loops. The SLPP protocol checks packets from the originating switch and the peer switch in a [SMLT](/source/SMLT) configuration. Sending hello packets on a per VLAN basis allows SLPP to detect VLAN based network loops for un-tagged, as well as tagged IEEE 802.1Q VLAN link configurations. If a loop is detected, the associated port is shut down.

==Compatible equipment==
* [Avaya VSP 9000 Series](/source/Avaya_VSP_9000_Series) - Software version 3.0 or above
* [Avaya VSP 7000 Series](/source/Avaya_VSP_7000_Series) - Software version 10.0 or above
* [Avaya ERS 8600](/source/Avaya_ERS_8600) - Software version 4.1 or above<ref>[http://www.nortel.com/products/01/passport/8600/collateral/nn117720.pdf Nortel Enterprise Converged Networking] {{webarchive |url=https://web.archive.org/web/20080225063438/http://www.nortel.com/products/01/passport/8600/collateral/nn117720.pdf |date=February 25, 2008 }}</ref>
* Avaya ERS-8300 - Software version 4.0 or above
* Avaya ERS-5000 - Software version 6.3 or above
* [Avaya ERS 4000 series](/source/Avaya_ERS_4000_series) - Software version 5.6.2 or above
* [Avaya ERS-3500](/source/ERS_3500_and_ERS_2500_series) - Software version 5.2.0 or above

==See also==
* [VLACP](/source/VLACP)

==References==
{{reflist}}

== Further reading ==
* {{cite web
  |title = United States Patent 20070230357
  |author=Lin, Chuh Yu |author2=Lapuh, Roger
  |website=Free Patents Online
  |date = October 4, 2007
  |url = http://www.freepatentsonline.com/y2007/0230357.html
  |access-date = 3 Sep 2011
  }}
* [http://www.google.com/patents?hl=en&lr=&vid=USPATAPP11394816&id=Wz-hAAAAEBAJ&oi=fnd&dq=%22Simple+Loop+Prevention+Protocol%22&printsec=abstract#v=onepage&q=%22Simple%20Loop%20Prevention%20Protocol%22&f=false Simple Loop Prevention Protocol]{{dead link|date=January 2025|bot=medic}}{{cbignore|bot=medic}} Google Patents
* [http://blog.michaelfmcnamara.com/2007/12/simple-loop-prevention-protocol-slpp/ Simple Loop Prevention Protocol (SLPP)]
* [https://unreachabledestination.blogspot.com/2009/08/nortel-simple-loop-prevention-protocol_2667.html Nortel "Simple Loop Prevention Protocol" (SLPP)]
* [http://support.avaya.com/css/P8/documents/100100707 Switch Clustering Design Best Practices]
* [https://web.archive.org/web/20111003174710/http://blog.axiomdynamics.com/2011_07_01_archive.html Quick Nortel MLT (Link Aggregation) Reference]
* [http://support.avaya.com/css/P8/documents/100100707 Switch Clustering Design Best Practices]

==External links==
{{Wiktionary|SLPP}}
* [http://support.avaya.com/css/P8/documents/100101601 Switch Clustering using Split Multi-Link Trunking (SMLT) with ERS 8600, 8300, 5x00 and 1600 Series Technical Configuration Guide]

{{Avaya}}

Category:Avaya
Category:Nortel protocols
Category:Link protocols

{{telecomm-infrastructure-stub}}

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Adapted from the Wikipedia article [Simple Loop Prevention Protocol](https://en.wikipedia.org/wiki/Simple_Loop_Prevention_Protocol) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Simple_Loop_Prevention_Protocol?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.