System
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Devices that Support Resiliency
The following Mitel IP devices support resiliency:
• All 50xx, 51xx and 52xx series IP Phones
• Navigator
• 5550 IP Console
• 5410/15 and 5412/48 IP PKMs
• 5305 and 5310 IP Conference Units
• Teleworker
Although only 3300 ICPs, Release 4.0 or later can be resilient controllers, resilient clusters can
also contain pre-4.0 3300 ICPs and Mitel legacy SX-2000 PBXs. These devices cannot function
as secondary controllers, but they can be part of a resilient solution as boundary nodes and
transit nodes.
Spanning Tree Protocol (STP)
The Rapid Spanning Tree protocol is supported on the CXi and MXe controllers. STP is not
supported on pre-release 5.0 ICPs, 3300 CX or the 100-user ICP. You must exercise care
when integrating an ICP that does not support STP or has STP disabled, into a network that
is running STP.
About STP
In an Ethernet network that is not using STP, multiple active paths between devices are not
allowed since multiple paths will cause network loops.
Network loops are unacceptable because a broadcast or multicast packet sent from Station
“A” to Station “B” will be forwarded by Switch “B” to Station “B” and also back to Switch “A”.
When Switch “A” receives the packet, it will then forward the packet back to Switch “B” and the
cycle will repeat for infinity causing a broadcast storm.
The Spanning Tree Protocol (STP) is a Layer 2 Link Level management protocol specified by
the IEEE (802.1D) that runs on bridges and switches. STP allows for physical path redundancy
by placing redundant network paths into a standby mode by blocking traffic on redundant ports.
Should a currently active network path fail due to a Bridge/Switch failure or a network cabling
failure, STP will enable the network path that was previously held in a standby mode and
network connectivity will be restored. The following figure depicts how STP breaks a potential
network loop by blocking traffic on one of the ports on Switch “B”.
Note: Resiliency is an IP solution that does not support ONS, DNIC and older 40xx-series
IP Phones.
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