BPDUs through MX250 in Routed Mode

[TheAlchemist]

Wanted to confirm whether BPDUs for Spanning Tree Protocol pass through Meraki MX250 in a "Routed" mode ? As in Routed mode MX acts like a layer 3 device and does not really participate in any layer 2 control process of traffic transfer.

Infact BPDU frames are dropped and do not traverse MX appliance in "Routed Mode."

Its only in "Passthrough or VPN Concentrator" mode when MX acts as a layer 2 Bridge that MX will forward BPDUs as received within the broadcast domain that they were received on.

[ww]

Not between lan - wan

But on the lan ports its possible https://documentation.meraki.com/MX/Networks_and_Routing/MX_Layer_2_Functionality#Spanning_Tree_Prot...)

If the MX received BPDUs on the LAN, these BPDUs will be re-forwarded within the broadcast domain that they were received on

[TheAlchemist]

I read the article  and thought that it is mentioned when MX is running in "Passthrough or VPN Concentrator" mode where MX acts like layer 2 Bridge  and thus forward Bridge Protocol data Units coming from connected switches.

[KarstenI]

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Infact BPDU frames are dropped and do not traverse MX appliance in "Routed Mode."

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There is an important "it depends". On the MX, you need to have the native VLAN enabled on the ports that connect to MS switches, as BPDUs are transferred only untagged. Then the BPDUs are passed which is needed to build the Meraki-suggested redundant setup.

https://cyber-fi.net/index.php/2022/03/13/how-to-connect-the-meraki-mx-to-ms-switches/