Users Guide

176 Network Administration: Port Settings
FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Dell Astute\User
Guide\Dell_Astute_Network_Admin_PortSettings.fm
DELL CONFIDENTIAL – PRELIMINARY 8/9/16 - FOR PROOF ONLY
The purpose of UDLD is to detect ports on which the neighbor does not
receive traffic from the local device (unidirectional link) and to shut down
those ports.
All connected devices must support UDLD for the protocol to successfully
detect unidirectional links. If only the local device supports UDLD, it is not
possible for the device to detect the status of the link. In this case, the status
of the link is set to undetermined. The user can configure whether ports in
the undetermined state are shut down or merely trigger notifications.
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 of 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 is unidirectional, the port is shut down.
– If the link is undetermined, the port is not shut down. Its status is
changed to undetermined and a notification is sent.
• Aggressive
If the link is unidirectional or undetermined, the port is shut down.