Rogue VLAN

Twitch
Building a reputation

Rogue VLAN

Morning everyone. Has anyone seen a situation where access points report a DHCP problem with a VLAN that doesn't exist? I have a site that is reporting a problem with some clients not being able to receive IP addresses from VLAN 4. The problem is, VLAN 4 does not exist in the environment.

 

Twitch_1-1633437677381.png

 

Twitch_2-1633437710369.png

I have looked everywhere on devices in this network to make sure that VLAN 4 is not configured, and sure enough I can't find it anywhere.

 

This does not impact performance in any way, since clients are receiving IPs from the correct VLAN. I'm just curious where this might be originating from more than anything. There also does not appear to be any way to clear the notification, either.

 

Has anyone else seen this happening?

 

Thanks.

 

Twitch

5 REPLIES 5
BrandonS
Kind of a big deal

Did you click “See request logs”?  Seems there may be a clue there.

Twitch
Building a reputation

Hey @BrandonS - sure did. The second screenshot above is what you find there. Not much to go on.

BrandonS
Kind of a big deal

Ah, I see now.  What about the 5/5 link in the second screenshot?  Anything good there?

Twitch
Building a reputation

That lists the MACs for an Apple device, most likely a cell phone, that was trying to get an IP from VLAN 4.

 

I wonder if it's because some strange config on the phone itself? We have had some contractors working in our shop on a new piece of equipment.

 

 

@Twitch If you have a trunk port anywhere on your network that is configured with allowed VLANS as "all" then you technically have 4094 possible VLANS on your network.

 

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Meraki CMNO, Ruckus WISE, Sonicwall CSSA, Allied Telesis CASE & CAI
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