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Table 116. Troubleshooting VLT (continued)
Description Behavior at Peer Up Behavior During Run Time Action to Take
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.
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.
Unit ID mismatch
The VLT peer does not boot
up. The VLTi is forced to a
down state.
A syslog error message is
generated.
The VLT peer does not boot
up. The VLTi is forced to a
down state.
A syslog error message is
generated.
Verify the unit ID is correct
on both VLT peers. Unit ID
numbers must be sequential
on peer units; for example, if
Peer 1 is unit ID “0”, Peer 2
unit ID must be “1’.
Version ID mismatch A syslog error message and an
SNMP trap are generated.
A syslog error message and an
SNMP trap are generated.
Verify the Dell EMC
Networking OS software
versions on the VLT peers
is compatible. For more
information, refer to the
Release Notes for this
release.
VLT LAG ID is not configured
on one VLT peer
A syslog error message is
generated. The peer with
the VLT configured remains
active.
A syslog error message is
generated. The peer with
the VLT configured remains
active.
Verify the VLT LAG ID is
configured correctly on both
VLT peers.
VLT LAG ID mismatch
The VLT port channel is
brought down.
A syslog error message is
generated.
The VLT port channel is
brought down.
A syslog error message is
generated.
Perform a mismatch check
after the VLT peer is
established.
Specifying VLT Nodes in a PVLAN
You can configure VLT peer nodes in a private VLAN (PVLAN). VLT enables redundancy without the implementation of
Spanning Tree Protocol (STP), and provides a loop-free network with optimal bandwidth utilization.
Because the VLT LAG interfaces are terminated on two different nodes, PVLAN configuration of VLT VLANs and VLT LAGs
are symmetrical and identical on both the VLT peers. PVLANs provide Layer 2 isolation between ports within the same VLAN.
A PVLAN partitions a traditional VLAN into sub-domains identified by a primary and secondary VLAN pair. With VLT being a
Layer 2 redundancy mechanism, support for configuration of VLT nodes in a PVLAN enables Layer 2 security functionalities. To
achieve maximum VLT resiliency, you should configure the PVLAN IDs and mappings to be identical on both the VLT peer nodes.
The association of PVLAN with the VLT LAG must also be identical. After the VLT LAG is configured to be a member of either
the primary or secondary PVLAN (which is associated with the primary), ICL becomes an automatic member of that PVLAN on
both switches. This association helps the PVLAN data flow received on one VLT peer for a VLT LAG to be transmitted on that
VLT LAG from the peer.
You can associate either a VLT VLAN or a VLT LAG to a PVLAN. First configure the VLT interconnect (VLTi) or a VLT LAG by
using the peer-link port-channel id-number command or the VLT VLAN by using the peer-link port-channel
id-number peer-down-vlan vlan interface number command and the switchport command. After you specify
the VLTi link and VLT LAGs, you can associate the same port channel or LAG bundle that is a part of a VLT to a PVLAN by using
the interface interface and switchport mode private-vlan commands.
When a VLTi port in trunk mode is a member of symmetric VLT PVLANs, the PVLAN packets are forwarded only if the PVLAN
settings of both the VLT nodes are identical. You can configure the VLTi in trunk mode to be a member of non-VLT PVLANs
if the VLTi is configured on both the peers. MAC address synchronization is performed for VLT PVLANs across peers in a VLT
domain.
Keep the following points in mind when you configure VLT nodes in a PVLAN:
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Virtual Link Trunking (VLT)