Service Manual

In the case of a primary VLT switch failure, the secondary switch starts sending BPDUs with its own bridge ID and inherits all the
port states from the last synchronization with the primary switch. An access device never detects the change in primary/secondary
roles and does not see it as a topology change.
The following examples show the RSTP conguration that you must perform on each peer switch to prevent forwarding loops.
Congure RSTP on VLT Peers to Prevent Forwarding Loops (VLT Peer 1)
Dell_VLTpeer1(conf)#protocol spanning-tree rstp
Dell_VLTpeer1(conf-rstp)#no disable
Dell_VLTpeer1(conf-rstp)#bridge-priority 4096
Congure RSTP on VLT Peers to Prevent Forwarding Loops (VLT Peer 2)
Dell_VLTpeer2(conf)#protocol spanning-tree rstp
Dell_VLTpeer2(conf-rstp)#no disable
Dell_VLTpeer2(conf-rstp)#bridge-priority 0
Conguring VLT
To congure VLT, use the following procedure.
Prerequisites:
Before you begin, make sure that both VLT peer switches are running the same Dell Networking OS version and are congured for
RSTP as described in RSTP Conguration. For VRRP operation, ensure that you congure VRRP groups and L3 routing on each VLT
peer as described in VLT and VRRP interoperability in the Conguration Notes section.To congure VLT and create a VLT domain in
which two S3048–ON switches are physically connected and treated as a single port channel by access devices, congure the
following settings on each VLT peer device.
1. Congure the VLT interconnect for the VLT domain. The primary and secondary switch roles in the VLT domain are
automatically assigned after you congure both sides of the VLTi.
NOTE: If you use a third-party ToR unit, to avoid potential problems if you reboot the VLT peers, Dell recommends
using static LAGs on the VLTi between VLT peers.
2. Enable VLT and create a VLT domain ID. VLT automatically selects a system MAC address.
3. Congure a backup link for the VLT domain.
4. (Optional) Manually recongure the default VLT settings, such as the MAC address and VLT primary/ secondary roles.
5. Connect the peer switches in a VLT domain to an attached access device (switch or server).
Conguring a VLT Interconnect
To congure a VLT interconnect, follow these steps.
1. Congure the port channel for the VLT interconnect on a VLT switch and enter interface conguration mode.
CONFIGURATION mode
interface port-channel id-number
Enter the same port-channel number congured with the peer-link port-channel command as described in Enabling
VLT and Creating a VLT Domain.
NOTE: To be included in the VLTi, the port channel must be in Default mode (no switchport or VLAN assigned).
2. Remove an IP address from the interface.
INTERFACE PORT-CHANNEL mode
no ip address
3. Add one or more port interfaces to the port channel.
INTERFACE PORT-CHANNEL mode
Virtual Link Trunking (VLT)
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