Addendum

• Provides fast convergence if either the link or a device fails.
• Optimized forwarding with virtual router redundancy protocol (VRRP).
• Provides link-level resiliency.
• Assures high availability.
CAUTION: Dell Networking does not recommend enabling Stacking and VLT simultaneously. If
you enable both features at the same time, unexpected behavior occurs.
As shown in the following example, VLT presents a single logical Layer 2 domain from the perspective of
attached devices that have a virtual link trunk terminating on separate chassis in the VLT domain.
However, the two VLT chassis are independent Layer2/Layer3 (L2/L3) switches for devices in the
upstream network. L2/L3 control plane protocols and system management features function normally in
VLT mode. Features such as VRRP and internet group management protocol (IGMP) snooping require
state information coordinating between the two VLT chassis. IGMP and VLT configurations must be
identical on both sides of the trunk to ensure the same behavior on both sides.
The following example shows VLT deployed on S4810 S4820T switches. The S4810 S4820T switches
appear as a single virtual switch from the point of view of the switch or server supporting link aggregation
control protocol (LACP).
Figure 3. VLT on S4810 S4820T Switches
VLT on Core Switches
You can also deploy VLT on core switches.
Uplinks from servers to the access layer and from access layer to the aggregation layer are bundled in
LAG groups with end-to-end Layer 2 multipathing. This set up requires “horizontal” stacking at the access
layer and VLT at the aggregation layer such that all the uplinks from servers to access and access to
Virtual Link Trunking (VLT)
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