The default mode of a switch is “forward first then verify’’. Enabling UDLD link-up will default to “forward first then
verify”. To change the mode to “verify then forward”, you need to configure using the commands found in section
6.72.
NOTE:
Link-UP data traffic will resumed after probing the link partner completes. All other protocols
running will see the port as down.
UDLD time delay
UDLD protocol informs the link partner simultaneously as it detects a state change from unidirectional to
bidirectional traffic. Additional packet exchanges will be carried out by UDLD in addition to the existing UDLD
exchanges whenever state changes from unidirectional to bidirectional.
Table 22: Peer state transition timings
Interval Time
Interval 1
Interval 1 + delta
Interval 2
Interval 3
5 sec
5+(<5) sec*
10 sec
15 sec
With triggered
updates
State = blockedPeer
State = blocked
Inform PeerState =
unblockedPeer State
= unblocked
Regular UDLD TX
Regular UDLD TX
Without triggered
updates
State = blockedPeer
State = blocked
State =
unblockedPeer State
= blocked
Inform PeerState =
unblockedPeer State
= unblocked
Regular UDLD TX
*delta is the time when the unblock event occurs on local side
Restrictions
• There is no support available when configuring this mode from the web and menu interface.
• There are no new packet types are introduced with UDLD.
• There are no new UDLD timers being introduced.
UDLD configuration commands
Syntax:
Switch(config)# link-keepalive mode [verify-then-forward | forward-then-verify]
This command configures the link-keepalive mode.
Link-keepalive provides two modes of operation;
verify-then-forward
and
forward-then-verify
.
When using the
verify-then-forward
mode, the port is in a blocking state until the link configured for UDLD
establishes bidirectional communication. When using the
forward-then-verify
mode, the port forwards the
data then verifies the status of the link-in state.
When a unidirectional state is detected, the port is moved to a blocked state.
When a bidirectional state is detected, the data is forwarded without interruption.
Syntax:
Switch(config)# link-keepalive mode verify-then-forward
216
Aruba 2930F / 2930M Management and Configuration Guide
for ArubaOS-Switch 16.08
