QTech QSW-2800 series, Configuration Manual

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Chapter 53 ULSM Configuration
53.1 Introduction to ULSM
ULSM (Uplink State Monitor) is used to process the port state synchronization. Each ULSM
group is made up of the uplink port and the downlink port, both the uplink port and the
downlink port may be multiple. The port may be a physical port or a port channel, but it can not
be a member port of a port channel, and each port only belongs to one ULSM group.
The uplink port is the monitored port of ULSM group. When all uplink ports are down or there
is no uplink port in ULSM group, ULSM group state is down. ULSM group state is up as long
as one uplink port is up.
The downlink port is the controlled port, its state changes along with Up/Down of ULSM group
and is always the same with ULSM group state.
ULSM associates with ULPP to enable the downstream device to apperceive the link problem
of the upstream device and process correctly. As the picture illustrated, SwitchA configures
ULPP, here the traffic is forwarded by port A1. If the link between SwitchB and Switch D has
the problem, SwitchA can not apperceive the problem of the upstream link and sequentially
forward the traffic from port A1, cause traffic losing.
Configuring ULSM on SwitchB can solve the above problems. The steps are: set port B5 as
the uplink port of ULSM group, port B6 as the downlink port. When the link between SwitchB
and SwitchD has the problem, both the downlink port B6 and the state of ULSM group are
down. It causes Switch A on which ULPP is configured to process uplink switchover and avoid
the data dropped.