Concept Guide

Non-VLT ARP Sync
In the Dell Networking OS version 9.2(0.0), ARP entries (including ND entries) learned on other ports are synced with the VLT peer to
support station move scenarios.
Prior to Dell Networking OS version 9.2.(0.0), only ARP entries learned on VLT ports were synced between peers.
Additionally, ARP entries resulting from station movements from VLT to non-VLT ports or to dierent non-VLT ports are learned on the
non-VLT port and synced with the peer node. The peer node is updated to use the new non-VLT port.
NOTE: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.
RSTP Conguration
RSTP is supported in a VLT domain.
Before you congure VLT on peer switches, congure RSTP in the network. RSTP is required for initial loop prevention during the VLT
startup phase. You may also use RSTP for loop prevention in the network outside of the VLT port channel. For information about how to
congure RSTP, Rapid Spanning Tree Protocol (RSTP).
Run RSTP on both VLT peer switches. The primary VLT peer controls the RSTP states, such as forwarding and blocking, on both the
primary and secondary peers. Dell Networking recommends conguring the primary VLT peer as the RSTP primary root device and
conguring the secondary VLT peer as the RSTP secondary root device.
BPDUs use the MAC address of the primary VLT peer as the RSTP bridge ID in the designated bridge ID eld. The primary VLT peer sends
these BPDUs on VLT interfaces connected to access devices. The MAC address for a VLT domain is automatically selected on the peer
switches when you create the domain.
Congure both ends of the VLT interconnect trunk with identical RSTP congurations. When you enable VLT, the show spanning-
tree rstp brief
command output displays VLT information.
Preventing Forwarding Loops in a VLT Domain
During the bootup of VLT peer switches, a forwarding loop may occur until the VLT congurations are applied on each switch and the
primary/secondary roles are determined.
To prevent the interfaces in the VLT interconnect trunk and RSTP-enabled VLT ports from entering a Forwarding state and creating a
trac loop in a VLT domain, take the following steps.
1 Congure RSTP in the core network and on each peer switch as described in Rapid Spanning Tree Protocol (RSTP).
Disabling RSTP on one VLT peer may result in a VLT domain failure.
2 Enable RSTP on each peer switch.
PROTOCOL SPANNING TREE RSTP mode
no disable
3 Congure each peer switch with a unique bridge priority.
PROTOCOL SPANNING TREE RSTP mode
bridge-priority
Virtual Link Trunking (VLT)
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