Reference Guide

318 | 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.