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fjulianom
fjulianom
Explorer II
June 17, 2025
Question

Two doubs about MCLAG FortiSwitch

  • June 17, 2025
  • 3 replies
  • 2353 views

Hi community,

 

I am going to implement many FortiSwitches as access switches. I have read that FortiSwitches supports MCLAG but not stack. Then, my first question is:

 

1. I am thinking of configuring them as independent switches, not MCLAG, because when they work as access switches the advantages of MCLAG are not so evident. I still need IP for every switch, users will be connected to only one switch, not dual home as servers, and the high-reliability offered by MCLAG I think is good for data centers and servers, but not needed for campus access switches. What do you think? By the way, they will managed by FortiGate/FortiLink.

https://www.qsfptek.com/qt-news/switch-stacking-vs-mlag.html

 

Second doubt:

2. I have read in the following Fortinet link:

There is a maximum of two FortiSwitch models per MCLAG.

Is it a typo? Does it means two FortiSwitch units? Only two?

https://docs.fortinet.com/document/fortiswitch/7.2.8/administration-guide/860027/mclag

 

Regards,

Julián

3 replies

Anthony_E
Staff
Anthony_E
Staff
June 20, 2025

Hello Julian,


Thank you for using the Community Forum. I will seek to get you an answer or help. We will reply to this thread with an update as soon as possible.


Thanks,

Best Regards
Jean-Philippe_P
Staff & Editor
Jean-Philippe_P
Staff & Editor
June 21, 2025

Hello,

 

We are still looking for an answer to your question.

 

We will come back to you ASAP.

 

Thanks,

Jean-Philippe - Fortinet Community Team
ebilcari
Staff
ebilcari
Staff
June 22, 2025

You can refer to this section of the guide that shows recommended topologies when a FGT is used, FortiLink guide, and for deploying MCLAG.

The limit of two refers to the number of switches that can participate in a single Multichassis LAG (MC-LAG), which is typically used at the distribution layer and is a common standard across various vendors.

Emirjon
    fjulianom
    fjulianomAuthor
    Explorer II
    June 25, 2025

    Hi community,

     

    I found this topology, which is two FortiGate units and many FortiSwitches which don't support MCLAG, as my situation:

     

    fortilink.PNG

     

    The guide doesn't explain in detail. Do the FortiSwitch units behave as a stack? I will have two FortiSwitches. Because I am going to connect servers which will be dual homed to both switches. I have always connected the servers to both MLAG switches or a stack of two switches (other vendors). Now with Fortinet I don't know if my two FortiSwitch units and this topology they will going to behave as a stack for dual homed servers.

     

    Regards,

    Julián

     

    ebilcari
    Staff
    ebilcari
    Staff
    June 25, 2025

    If the FSW models you have do not support MCLAG, I don't think it will be possible to dual home a server. You will need FSW models that support MCLAG as shown here.

    Emirjon
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