Port Management
UDLD
Cisco 350XG & 550XG Series 10G Stackable Managed Switches
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10
UDLD States and Modes
Under the UDLD protocol, ports are assigned the following states:
•
Detection
—System is attempting to determine whether the link is
bidirectional or unidirectional. This is a temporary state.
•
Bidirectional
—Traffic sent by a local device is known to be received by its
neighbor, and traffic from the neighbor is received by the local device.
•
Shutdown
—The link is unidirectional. Traffic sent by a local device is
received by its neighbor, but traffic from the neighbor is not received by the
local device.
•
Undetermined
—The system cannot determine the state of the port,
because one of the following is occurring:
-
The neighbor does not support UDLD.
or
-
The neighbor does not receive traffic from the local device.
The UDLD action in this case depends on the UDLD mode of the device as
explained below.
UDLD supports the following modes of operation:
•
Normal
If the link state of the port is determined to be bi-directional and the UDLD
information times out while the link on the port is still up, UDLD tries to re-
establish the state of the port.
•
Aggressive
If the link state of the port is determined bi-directional and the UDLD
information times out, UDLD shuts down the port after an extended period
of time, when it can determine that the link is faulty. The port state for UDLD
is marked as undetermined.
UDLD is enabled on a port when one of the following occurs:
•
The port is a fiber port and UDLD is enabled globally.
•
The port is a copper port and you specifically enable UDLD on it.
