Service Manual

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.
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.
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
channel-member interface
interface: specify one of the following interface types:
Virtual Link Trunking (VLT)
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