QTECH QSW-3400 Инструкция по настройке - Manual (Page 405)

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Chapter 54 ULPP Configuration
54.1 Introduction to ULPP
Each ULPP group has two uplink ports, they are master port and slave port. The port may be a
physical port or a port channel. The member ports of ULPP group have three states:
Forwarding, Standby, Down. Normally, only one port at the forwarding state, the other port is
blocked at the Standby state. When the master port has the link problem, the master port
becomes down state, and the slave port is siwthed to forwarding state.
the using scene of ULPP
The above figure uses the double-uplink network, this is the typical application scene of ULPP.
SwitchA goes up to SwitchD through SwitchB and SwitchC, port A1 and port A2 are the uplink
ports. SwitchA configures ULPP, thereinto port A1 is set as the master port, port A2 is set as
the slave port. When port A1 at forwarding state has the problem, switch the uplink at once,
port A2 turns into forwarding state. After this, when recovering the master port, if the
preemption mode is not configured, port A2 keeps the Forwarding state, port A1 turns into the
Standby state.
After the preemption mode is enabled, so as to the master port preempts the slave port when it
recovered from the problem. For avoiding the frequent uplink switch caused by the abnormity