Meraki DHCP server gives addresses from the wrong pool

[EricTronic]

Hi all,

A client of mine has an MX100 firewall, on which 2 VLANs are configured on the inside. On each VLAN interface a DHCP pool is active. Now it _seems_ that something strange is happening....

Could it be, anyone ever heard of, that when on the first interface, if the DHCP pool is exhausted there, an MX100 starts giving out addresses from the DHCP pool from the other VLAN? Some tablets obtain an address of the other network segment, which they are not connected to. The error could also lay in a wrongfully configured switch, putting untagged frames in the wrong VLAN. I don't know that yet.

Wanna make sure the error is not in the Meraki, before I start tearing his network apart :-)

If no one has ever seen this behaviour on a Meraki MX100, I can be sure the error lies in the network.

If someone has seen this before, please tell me...

Greetz Erik

[omz]

Hi

Meraki won't give out IP addresses from another pool if the given pool is exhausted.

The error must be coming from how the VLAN is being mapped.

You mentioned tablets .. so it wireless clients .. check how the SSID is being tagged.

Is it Meraki full-stack i.e MR,MS, and MX? Or just the MX?

[EricTronic]

Hi,

All Meraki, no exceptions. Switch says it sees only 1 DHCP server. All MR42 do tag all VLANs, but there are some trunks in between the MR, the MS and the MX I don't know about yet. Maybe some native VLAN problem.....

Greetz Erik

[omz · Accepted solution]

All Meraki should be easy to tshoot...

Yeh looks like vlan tagging issue. 

Surely MX won't hand out IP addresses from another pool if one is exhausted.

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