Reference Guide

868 | Virtual Link Trunking (VLT)
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Troubleshooting VLT
Use the following information to help troubleshoot different VLT issues that may occur.
Note: For information on VLT failure mode timing and its impact, contact your Dell Networking
representative.
Description Behavior at Peer Up
Behavior During Run
Time Action to Take
Bandwidth monitoring A syslog error message and
an SNMP trap is generated
when the VLTi bandwidth
usage goes above the 80%
threshold and when it drops
below 80%.
A syslog error message and
an SNMP trap is generated
when the VLTi bandwidth
usage goes above its
threshold.
Depending on the traffic that
is received, the traffic can be
offloaded inVLTi.
Domain ID mismatch The VLT peer does not boot
up. The VLTi is forced to a
down state.
A syslog error message and
an SNMP trap are generated.
The VLT peer does not boot
up. The VLTi is forced to a
down state.
A syslog error message and
an SNMP trap are generated.
Verify that the domain ID
matches on both VLT peers.
FTOS Version mismatch A syslog error message is
generated.
A syslog error message is
generated.
Follow correct upgrade
procedure for unit with
mismatched FTOS version.
Remote VLT port channel
status
N/A N/A Use the show vlt detail and
show vlt brief commands to
view VLT port channel status
information.
Spanning tree mismatch at
global level
All VLT port channels go
down on both VLT peers. A
syslog error message is
generated.
No traffic is passed on the
port channels.
A one-time informational
syslog message is generated.
During run time, a loop may
occur as long as the mismatch
lasts.
To resolve, enable RSTP on
both VLT peers.
Spanning tree mismatch at
port level
A syslog error message is
generated.
A one-time informational
syslog message is generated.
Correct the spanning tree
configuration on the ports.
System MAC mismatch A syslog error message and
an SNMP trap are generated.
The VLT domain will not be
formed. The VLTi will be in a
down state.
A syslog error message and
an SNMP trap are generated.
Verify that the unit ID of VLT
peers is not the same on both
units and that the MAC
address is the same on both
units.