How to set up Virtual Link Trunking (VLT) on Dell Networking OS9 Force10 Switches


How to set up Virtual Link Trunking (VLT) on Dell Networking OS9 Force10 Switches


This article explains how to set up Virtual Link Trunking (VLT) on Dell Networking OS9 Force10 switches.




The steps in this article are applicable to Force 10 switches that support Virtual Link Trunking. This article does not contain the requirements for VLT. It is recommended that a user verifies the requirements for VLT before implementing these steps. Full manuals can be accessed via the support site.


VLT Configuration Overview


1. Optional not required but preferred: Enable RSTP and configure RSTP bridge priority on the primary and secondary VLT peer switches
2. Configure the VLT interconnect for the VLT domain, a static LAG between the VLT switches
3. Configure the VLT domain
4. Configure the LAG for the Connected Device
5. Verifying and Monitoring


Optional not required but preferred: Configuring RSTP on the VLT peer switches

Command Purpose
Force10# configure Enter configuration mode.
Force10(conf)# protocol spanning-tree rstp Enter RSTP configuration mode.
Force10(conf-rstp)# bridge-priority 4096 (primary peer)
Force10(conf-rstp)# bridge-priority 8192 (secondary peer)
Optional: configure RSTP bridge priority.*These priorities are not unique to the VLT pair and are used to show preference for the primary. Use a higher multiple of 4096 to avoid the primary becoming the root bridge.
Force10(conf-rstp)# no disable Enable the spanning tree protocol version.


Configure VLT interconnect for the VLT domain (a Static Lag between the VLT switches)


Command Purpose
Force10# configure Enter configuration mode.
Force10(conf)# interface range fortyGigE 0/56 , fortyGigE 0/60 Enter interface configuration mode. Be aware of the spaces needed before and after the comma.
Force10(conf-if-range-fo-0/56,fo-0/60)# no shutdown Enable the range of interfaces.
Force10(conf-if-range-fo-0/56,fo-0/60)# interface port-channel 100 Enter port-channel configuration mode.
Force10(conf-if-po-100)# channel-member fortyGigE 0/56,60 Add the physical interfaces to the port-channel.
Force10(conf-if-po-100)# no shutdown Enable the port-channel.


Warning: Do not add any VLANs to the VLT Interconnect. The VLTi interface manages VLAN tagged/untagged traffic automatically between peers. Manually adding any VLAN configuration has been shown to disrupt traffic flow. If a VLAN configuration has been added to the VLTi, the recommended recovery procedure is as follows for both VLT members:
  1. Remove the VLAN configuration from the interface
  2. Save the configuration
  3. Reload the VLT member


Configure VLT Domain

Command Purpose
Force10# configure Enter configuration mode.
Force10(conf)# vlt domain 1 Enter VLT domain configuration mode for domain ID 1-1000.
Force10(conf-vlt-domain)# primary-priority 10 (primary peer)
Force10(conf-vlt-domain)# primary-priority 20 (secondary peer)
Optional: specify the VLT priority for each peer switch. 1-65535 (highest to lowest)
Force10(conf-vlt-domain)# back-up destination 1.1.1.2 (primary peer)
Force10(conf-vlt-domain)# back-up destination 1.1.1.1 (secondary peer)
Specify the management IP address of the peer switch. This sets up the HeartBeat that monitors system up.
Force10(conf-vlt-domain)# peer-link port-channel 100 Associate the VLTi LAG to the VLT domain.

Note: Optional - When you create a VLT domain on a switch. Dell Networking OS automatically creates a VLT-system MAC address used for the internal system operation. You can explicitly configure a default MAC address for the domain by entering a new MAC address. Use the system-mac command. Force10(conf-vlt-domain)# system-mac mac-address Also, configure the same MAC address on the VLT peer switch. This command is used to minimize the time required for the VLT system to synchronize the default MAC address of the VLT domain on both peer switches when one peer switch reboots.


Configure the LACP LAG on both VLT Peers for the Connecting Device

Command Purpose
Force10# configure Enter configuration mode
Force10(conf)# interface tengigabit 0/20 Enter interface configuration mode
Force10(conf-if-te-0/20)# port-channel-protocol lacp Enter LACP configuration mode
Force10(conf-if-te-0/20-lacp)# port-channel 20 mode active Set the port-channel as "mode active" for LACP LAG
Force10(conf-if-te-0/20-lacp)# interface port-channel 20 Enter port-channel configuration mode
Force10(conf-if-po-20)# portmode hybrid Portmode hybrid allows the interface to pass tagged and untagged traffic
Force10(conf-if-po-20)# switchport switchport puts the interface in layer 2 mode
Force10(conf-if-po-20)# vlt-peer-lag port-channel 20 Assign the port-channel as a VLT port-channel
Force10(conf-if-po-20)#end Exit configuration mode
Force10# write Save configuration


You will need to add the VLT port channel interface to VLANs as needed for proper traffic flow to the connected device.


Note: These steps should be repeated on both VLT peers. The device connected across this LAG should setup in a LACP LAG. The device will not be aware it's connected to a VLT port-channel, it will perform like it's connected to a normal LACP port-channel.

Note: These steps should be repeated on both VLT peers. The device connected across this LAG should setup in a LACP LAG. The device will not be aware it's connected to a VLT port-channel, it will perform like it's connected to a normal LACP port-channel.

Verifying and Monitoring

Verifying VLT Domain Status:
Primary VLT Peer:

Force10# show vlt brief
VLT Domain Brief
-------------------------------------------------
Domain ID: 1
Role: Primary
Role Priority: 10
ICL Link Status: Up
Heartbeat Status: Up
VLT Peer Status: Up
Local System MAC address: 00:01:e8:8b:19:37
Remote System MAC address: 00:01:e8:8b:18:b9

Configured System MAC address: aa:11:22:33:44:55

Secondary VLT Peer:

Force10# show vlt brief
VLT Domain Brief
-------------------------------------------------
Domain ID: 1
Role: Secondary
Role Priority: 20
ICL Link Status: Up
Heartbeat Status: Up
VLT Peer Status: Up
Local System MAC address: 00:01:e8:8b:18:b9
Remote System MAC address: 00:01:e8:8b:19:37

Configured System MAC address: aa:11:22:33:44:55

Verifying VLT PDUs and errors:

Force10# show vlt statistics
-----------------------------------------------------
HeartBeat Messages Sent: 95446
HeartBeat Messages Received: 95440
ICL Hello's Sent: 95420
ICL Hello's Received: 95414
Domain Mismatch Errors: 0
Version Mismatch Errors: 0
Config Mismatch Errors: 0


Verifying VLT Backup Link status:

Primary VLT peer:

Force10# show vlt backup-link
VLT Backup Link
--------------------------------------------------
Destination: 1.1.1.2
Peer HeartBeat status: Up
HeartBeat Timer Interval: 1
HeartBeat Timeout: 3
UDP Port: 34998
HeartBeat Messages Sent: 95305
HeartBeat Messages Received: 95299



Secondary VLT peer:

Force10# show vlt backup-link
VLT Backup Link
--------------------------------------------------
Destination: 1.1.1.1
Peer HeartBeat status: Up
HeartBeat Timer Interval: 1
HeartBeat Timeout: 3
UDP Port: 34998
HeartBeat Messages Sent: 95305
HeartBeat Messages Received: 95299

Verifying Matching configuration on both VLT Peers:
Force10# show vlt mismatch






Article ID: HOW10660

Last Date Modified: 10/14/2019 02:02 PM

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