Meraki switch switchpot trunks

[ccraddock]

Dear community,

I had a quick question regarding the trunking mechanism on the Meraki switches. When you set a port to trunk mode and allow all vlans on that trunk, will it automatically allow vlans on the trunk as you assign ports to their respective vlan? For instance, if I assigned port 1 to vlan 300 and port 2 to vlan 400, will the trunks automatically start trunking for and forwarding for those vlans on the trunk? Or is it better to manually specify exactly which vlans are allowed on the trunk to make sure they are forwarding on that trunk?  On IOS I would just run a "show interfaces trunk" and a "show spanning-tree interface" to see what the forwarding action was on a specific interface. Unfortunately I cannot find a way to verify which vlans the trunks are forwarding for, its kind of annoying actually.

Thanks. 

[kYutobi]

If you allow all VLANs.  The trunk should allow them all even if you create new ones.

[ccraddock]

@kYutobi ,

Thanks for the reply! This begs the question: If there is no way to "create" vlans directly on the Meraki switch, is it safe to assume that all possible vlans are already "created" and that all you have to do is assign vlans to ports and trunks? Ive spent my entire career having to "create" vlans before they can be used, but the Meraki switches seem to already know about them ahead of time. I'm a little confused as to how that works.

Thanks.

[NolanHerring · Accepted solution]

It is slightly different on Meraki. On Cisco, yes you had to create. On Meraki, if you go to any switch port and assign it a VLAN that doesn't exist anywhere (routable etc.). Say for example you just create say VLAN 555 for fun.

Then that VLAN exists. so it in theory can no go over any trunk port. Of course if there is no SVI anywhere it won't go anywhere, but it works great for when you want to use a switch as a fiber to ethernet converter, or transient path for circuits etc.,

[ccraddock]

I see. So in essence no vlans (except 1) exist on a meraki switch until you either 1) create an SVI for that vlan or 2) assign a switchport to a specific vlan? In both cases, those vlans will be allowed on any trunk set to allow "all" vlans? Am I understanding that? If so I guess its not much different than in IOS where when you try to assign a port to a vlan that doesn't yet exists, the switch will just create it for you.

[NolanHerring]

Correct. Unless I'm wrong. 😃

[PERI_Admin]

I also have one question / issue which I'm not sure about.

Setup:

Firewall <--> (trunk allowed vlan 140, 141) Switch 1 MS130 (trunk all) <--> (trunk all) Coreswitch MS390 (trunk all) <--> (trunk all) Switch 2 MS130 (trunk allowed vlan 10, 140) <--> MR46

I can see the MAC address of the firewall interface in vlan 140 on Switch 1. But not on the Coreswitch or Switch 2. Seems as if the Coreswitch ignores VLAN140.

What is the right way to troubleshoot this?

I just configured one port of the Coreswitch as access vlan 140 port and then vlan140 was available also on Switch 2.