Users Guide

• You can only use one spanned VLAN from a PIM-enabled VLT node to an external neighboring PIM router.
• If you connect multiple spanned VLANs to a PIM neighbor, or if both spanned and non-spanned VLANs can access the PIM neighbor,
ECMP can cause the PIM protocol running on each VLT peer node to choose a dierent VLAN or IP route to reach the PIM neighbor.
This can result in issues with multicast route syncing between peers.
• Both VLT peers require symmetric Layer 2 and Layer 3 congurations on both VLT peers for any spanned VLAN.
• For optimal performance, congure the VLT VLAN routing metrics to prefer VLT VLAN interfaces over non-VLT VLAN interfaces.
• When using factory default settings on a new switch deployed as a VLT node, packet loss may occur due to the requirement that all
ports must be open.
• ECMP is not compatible on VLT nodes using VLT multicast. You must use a single VLAN.
Conguring VLT Multicast
To enable and congure VLT multicast, follow these steps.
1 Enable VLT on a switch, then congure a VLT domain and enter VLT-domain conguration mode.
CONFIGURATION mode
vlt domain domain-id
2 Enable peer-routing.
VLT DOMAIN mode
peer-routing
3 Congure the multicast peer-routing timeout.
VLT DOMAIN mode
multicast peer-routing—timeout value
value: Specify a value (in seconds) from 1 to 1200.
4 Congure a PIM-SM compatible VLT node as a designated router (DR). For more information, refer to Conguring a Designated
Router.
5 Congure a PIM-enabled external neighboring router as a rendezvous point (RP). For more information, refer to Conguring a Static
Rendezvous Point
.
6 Congure the VLT VLAN routing metrics to prefer VLT VLAN interfaces over non-VLT VLAN interfaces. For more information, refer to
Classify Trac.
7 Congure symmetrical Layer 2 and Layer 3 congurations on both VLT peers for any spanned VLAN.
Non-VLT ARP Sync
Synchronization for non-ARP routing table entries is supported on the switch.
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 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.
Virtual Link Trunking (VLT)
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