Non-Vlt Arp Sync; Rstp Configuration; Preventing Forwarding Loops In A Vlt Domain; Sample Rstp Configuration - Dell S4048–ON Configuration Manual

5. Configure a PIM-enabled external neighboring router as a rendezvous point (RP). For more information, refer to
Static Rendezvous Point.
6. Configure the VLT VLAN routing metrics to prefer VLT VLAN interfaces over non-VLT VLAN interfaces. For more information,
refer to Classify Traffic.
7. Configure symmetrical Layer 2 and Layer 3 configurations on both VLT peers for any spanned VLAN.

Non-VLT ARP Sync

ARP entries (including ND entries) learned on other ports are synced with the VLT peer to support station move scenarios.
NOTE: ARP entries learned on non-VLT, non-spanned VLANs are not synced with VLT peers.

RSTP Configuration

RSTP is supported in a VLT domain.
Before you configure VLT on peer switches, configure 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 configure RSTP, Rapid Spanning Tree Protocol
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 configuring the primary VLT peer as the RSTP primary root device and
configuring 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 field. 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 (refer to
Configure both ends of the VLT interconnect trunk with identical RSTP configurations. When you enable VLT, the show
spanning-tree rstp brief command output displays VLT information (refer to

Preventing Forwarding Loops in a VLT Domain

During the bootup of VLT peer switches, a forwarding loop may occur until the VLT configurations 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 traffic loop in a VLT domain, take the following steps.
1. Configure RSTP in the core network and on each peer switch as described in
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. Configure each peer switch with a unique bridge priority.
PROTOCOL SPANNING TREE RSTP mode
bridge-priority

Sample RSTP Configuration

The following is a sample of an RSTP configuration.
Using the example shown in the
device (switch or server) with its own RSTP bridge ID. BPDUs generated by an RSTP-enabled access device are only processed by
the primary VLT switch. The secondary VLT switch tunnels the BPDUs that it receives to the primary VLT switch over the VLT
interconnect. Only the primary VLT switch determines the RSTP roles and states on VLT ports and ensures that the VLT
interconnect link is never blocked.
912
Virtual Link Trunking (VLT)
(RSTP).
Enabling VLT and Creating a VLT
Overview section as a sample VLT topology, the primary VLT switch sends BPDUs to an access
Domain).
Verifying a VLT Configuration).
Rapid Spanning Tree Protocol
Configuring a
(RSTP).