View source for InterSwitch Trunk

'''InterSwitch Trunk''' ('''IST''') is one or more parallel point-to-point links ([[Link aggregation]]) that connect two switches together to create a single logical switch.  The IST allows the two switches to share addressing information, forwarding tables, and state information, permitting rapid (less than one second) fault detection and forwarding path modification. The link may have different names depending on the vendor. For example, Brocade calls this an Inter-Chassis Link (ICL).<ref>{{Cite web|url=http://www.brocade.com/forms/getFile?p=documents/white_papers/Brocade_Multi-Chassis_Trunking_WP.pdf|title=Broadcom Inc. &#124; Connecting Everything}}</ref> Cisco calls this a VSL (Virtual Switch Link).<ref>{{Cite web|url=http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/12.2SX/configuration/guide/vss.html#wp1062284|title = Catalyst 6500 Release 12.2SX Software Configuration Guide - Virtual Switching Systems (VSS) &#91;Cisco Catalyst 6500 Series Switches&#93;}}</ref>

Edge switches, servers or PCs see the two aggregate switches as one large switch.  This allows any vendor's equipment configured to use the IEEE 802.3ad static link aggregation protocol to connect to both switches and take advantage of load balancing, redundant connections.

The IST protocol was developed by [[Nortel]] (now acquired by [[Avaya]], which is now acquired by [[Extreme Networks]]) to enhance the capabilities of [[Link aggregation]],   and is required to be configured prior to configuring the [[SMLT]], [[DSMLT]] or [[R-SMLT]] functions on the two aggregate (core, distribution, or access) switches.  The edge equipment can be configured with any of the following; [[Multi-Link Trunking (MLT)]], [[DMLT]], IEEE 802.3ad static link aggregation, IEEE 802.3ad Static Gigabit EtherChannel (GEC), IEEE 802.3ad Static Fast EtherChannel (FEC), [[SMLT]], [[DSMLT]], and other static link aggregation protocols.

==Patent==
United States Patent 7173934

==Product support==
IST is supported on Nortel's Routing Switch 1600, 5000, 8300, [[Nortel ERS 8600| ERS 8600]], [[MERS 8600]] products and also on Avaya's Virtual Services Platform [[Avaya VSP-7000 System|VSP 7000]] and [[Avaya VSP-9000 System|VSP 9000]].

==See also==
* [[Avaya]]
* [[Avaya Government Solutions]]

==References==
{{Reflist}}

==External links==
{{Wiktionarypar|IST}}
{{commons|Avaya}}
* [https://web.archive.org/web/20110717093600/http://www.trcnetworks.com/nortel/Data/Swiches/8600/pdfs/network%20resilient.pdf Designing a Resilient Network]
* [https://web.archive.org/web/20110717093614/http://www.trcnetworks.com/nortel/Data/Swiches/8600/pdfs/Split_multi_Link_Trunking.pdf Passport 8600 Split Multi-Link Trunking]
* [https://archive.today/20130416062048/http://www.trends.com.ph/2006/07/nortel-secure-always-on-networking/ Always on Networking]

{{Avaya}}

[[Category:Avaya]]
[[Category:Ethernet]]
[[Category:Link protocols]]
[[Category:Network architecture]]
[[Category:Network topology]]
[[Category:Nortel protocols]]