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csantos1991

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October 2nd, 2025 16:17

Same vlt-mac in different switch pairs

Hi,

I'm new to dell switches, so I'm sorry if I'm making obvious questions.

I've found out in a customer a topology with 2 Spine Switches and 4 leaf switches. The leaf switches have a VLTi between them in pairs. So I have a VTLi between leaf1 and leaf2, and another VTLi between leaf3 and leaf4. 

The problem for me is that both of the pairs have the sabe vlt-mac address config. I know that each pair should have the same vlt-mac address. But I see the same vlt-mac on all of the 4 switches. Can this be an issue? From a theoretically point of view, for me is an issue. But since I'm new to the Dell Switches, maybe this is not relevant. 

Thanks in advance.

DELL-Charles R

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4.5K Posts

October 2nd, 2025 20:44

Hello,

 

We understand you have 4 leaf switches (2 VLT pairs) connected to 2 spine switches. The VLT-MAC addresses should not be the same across all four switches.  You would have 2 separate VLT domains, and each domain is required to use the same VLT-MAC address on its peer switches, but a unique VLT-MAC for the domain itself.

As an example, In a four-switch deployment:

  • VLT Domain 1 (Switches 1 and 2): Both Switch 1 and Switch 2 are configured with vlt-mac 00:11:22:33:44:55.
  • VLT Domain 2 (Switches 3 and 4): Both Switch 3 and Switch 4 are configured with vlt-mac 00:aa:bb:cc:dd:ee.

Using the same VLT-MAC across all four switches would cause network issues, as it would disrupt the ability to properly route and forward Layer 2 traffic between the two separate VLT domains

 

Here are a couple of documents with more information:

Dell EMC SmartFabric OS10 - Virtual Link Trunking - Reference Architecture Guide

https://infohub.delltechnologies.com/en-us/t/dell-emc-smartfabric-os10-virtual-link-trunking-refere…

Dell SmartFabric OS10 User Guide Release 10.5.6

 

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