Virtual Link Trunking (Vlt); Overview - Dell Force10 Z9000 Configuration Manual

Virtual Link Trunking (VLT)

Virtual Link Trunking (VLT)

Overview

Virtual link trunking (VLT) allows physical links between two chassis to appear as a single virtual link to
the network core. VLT reduces the role of Spanning Tree protocols by allowing LAG terminations on two
separate distribution or core switches, and by supporting a loop free topology. (A Spanning Tree protocol
is still needed to prevent the initial loop that may occur prior to VLT being established. After VLT is
established, RSTP may be used to prevent loops from forming with new links that are incorrectly
connected and outside the VLT domain.)VLT provides Layer 2 multipathing, creating redundancy through
increased bandwidth, enabling multiple parallel paths between nodes and load-balancing traffic where
alternative paths exist.
As shown in Figure
devices that have a virtual link trunk terminating on separate chassis in the VLT domain. However, the two
VLT chassis are independent 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
IGMP Snooping require state information to be coordinated between the two VLT chassis.
is supported on platforms
48-1, VLT presents a single logical Layer 2 domain from the perspective of attached
z
48
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