Dell X1000 Networking X-Series Switches User Guide - Page 177

How UDLD Works

Page 177 highlights

FILE LOCATION: C:\Users\gina\Desktop\Checkout_new\Dell Astute\User Guide\Dell_Astute_Network_Admin_PortSettings.fm 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. How UDLD Works When UDLD is enabled on a port, the following actions are performed: • UDLD initiates the detection state on the port. In this state, UDLD periodically sends messages on every active interface to all neighbors. These messages contain the device ID of all known neighbors. It sends these messages according to a user-defined message time. • UDLD receives UDLD messages from neighboring devices. It caches these messages until the expiration time (3 times message time) has passed. If a new message is received before the expiration time, the information in that message replaces the previous one. • When the expiration time expires, the device does the following with the information received: - If the neighbor message contains the local device ID-The link status of the port is set to bidirectional. - If the neighbor message does not contain the local device ID-The link status of the port is set to unidirectional, and the port is shut down. • If UDLD messages are not received from a neighboring device during the expiration time frame, the link status of the port is sent to undetermined and the following occurs: - Device is in normal UDLD mode: A notification is issued. - Device is in aggressive UDLD mode. The port is shut down. While the interface is in the bidirectional or the undetermined state, the device periodically sends a message each message time seconds. The above steps are performed over and over. A port that was shut down can be reactivated manually in the Port Configuration page. For more information, see Reactivating a Shutdown Port. DELL CONFIDENTIAL - PRELIMINARY 8/9/16 - FOR PROOF ONLY Network Administration: Port Settings 177

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Network Administration: Port Settings
177
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
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.
How UDLD Works
When UDLD is enabled on a port, the following actions are performed:
UDLD initiates the detection state on the port.
In this state, UDLD periodically sends messages on every active interface
to all neighbors. These messages contain the device ID of all known
neighbors. It sends these messages according to a user-defined message
time.
UDLD receives UDLD messages from neighboring devices. It caches these
messages until the expiration time (3 times message time) has passed. If a
new message is received before the expiration time, the information in
that message replaces the previous one.
When the expiration time expires, the device does the following with the
information received:
If the neighbor message contains the local device ID
—The link
status of the port is set to bidirectional.
If the neighbor message does not contain the local device ID
—The
link status of the port is set to unidirectional, and the port is shut
down.
If UDLD messages are not received from a neighboring device during the
expiration time frame, the link status of the port is sent to undetermined
and the following occurs:
Device is in normal UDLD mode:
A notification is issued.
Device is in aggressive UDLD mode.
The port is shut down.
While the interface is in the bidirectional or the undetermined state, the
device periodically sends a message each message time seconds. The above
steps are performed over and over.
A port that was shut down can be reactivated manually in the
Port
Configuration
page. For more information, see
Reactivating a Shutdown Port
.