SNR S2940-8G-v2 Switch Configuration Guide
ULPP Configuration
Chapter 59
ULPP Configuration
59.1 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.
Figure 59.1: 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
problem, the preemption delay mechanism is imported, and it needs to wait for some times before
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