Extending VLANs over an unmanaged switch

[yllw98stng]

We have a network which consists of primarily Cisco 3560X switches and Meraki MR34 wireless access points.  We have a handful of VLANs setup.  In one instance, a WAP was plugged into an unmanaged SD100D-08 switch.  I would have expected this to "break" our wireless access.  However, it appears everything is working as we'd want.

The switchport on the 3560X that the unmanaged switch is connected to is configured as a trunk port with the default VLAN of 1.  No matter which SSID/VLAN we connect to on the Meraki Access Points, we get assigned a proper IP in the VLAN that we'd expect.  If we connect a computer to the unmanaged switch, it gets an IP from VLAN 1, just as we would have wanted.

Why is this working?  I thought the unmanaged switch would drop all packets with VLAN headers?

[Jon Marshall · Accepted solution]

Jason

There is very little information on these switches but from the Install and Upgrade Guide -

The switch is configured to comply with 802.1p, VLAN tagged frames.

Now that could be taken any number of ways I admit but perhaps the switch will accept tagged frames on any of it's ports and simply pass them through.

Just a guess though.

Jon

[yllw98stng]

Thanks for the quick response Jon.  I have continued with my testing and connected two 3560X switches together with the same unmanaged switch in between them. I configured the 3560X ports as trunk ports and am able to pass all VLANs between the two 3560X switches with the unmanaged switch in between.

As you stated, it looks like the unmanaged switch is capable of handling the VLAN tagged frames and passing them out all connected ports.

Obviously this configuration is not best practice, but I guess it is pretty cool it's working that way.

Jason

[Jon Marshall]

Jason

Obviously this configuration is not best practice, but I guess it is pretty cool it's working that way.

Yes, although I don't think you want to have redundant connections to this switch as I'm not sure it even supports STP.

Jon