Synology NAS suddenly acts as DHCP server

[SmokyDiego]

Hello all, 

We have Synology NAS running on our network. 

For some reason, it became DHCP server couple times. Some time ago, I disabled DHCP Server plugin in Synology, but after couple months, Meraki is reporting that Synology became DHCP server again. 

I checked Synology once more and it DHCP module is really uninstalled, so it should not act like DHCP, but it became suddenly couple days ago.

Synology has static IP 10.0.6.55 connected via cable, and as per image below it is switching to different VLANS. 

Any suggestions how to proceed to get rid of this issue ?

[alemabrahao]

It's unusual for a Synology NAS to act as a DHCP server if the DHCP module is uninstalled.

As per your description, the Synology NAS is switching to different VLANs. This could potentially cause the NAS to act as a DHCP server on those VLANs. You might want to check the VLAN settings on your network switch and the NAS to ensure they are configured correctly.

Ensure that the Synology NAS is running the latest firmware. Sometimes, bugs in the firmware can cause unexpected behavior.

Some other services on the Synology NAS might be acting as a DHCP server. For example, if you're running a virtual machine or a Docker container on the NAS, they could potentially have a DHCP server running.

Consider doing a network traffic analysis to identify which service on the Synology NAS is acting as a DHCP server. Tools like Wireshark can help with this.

If none of the steps resolve the issue, it might be best to contact Synology's support. They can provide more specific guidance based on the exact model and configuration of your NAS.

[SmokyDiego]

Well, it should not act like DHCP at all, because it doesnt have DHCP plugin. 

I checked IP setting in Meraki and NAS itself - IP is assigned as static to one specific VLAN, static is same and correct in NAS and in Meraki too. 

So my guess is something in Meraki settings, not sure what exactly, because in VLAN setting I can see that only one specific VLAN has assigned static IP of Synology. 

[PhilipDAth]

Does your Synology NAS need to be connected to multiple VLANs?

It would be simpler to have it in a single VLAN, and configure the port that it plugs into on the network as an access port.

[SmokyDiego]

No, but is doing that itself - it is assigned to only one VLAN in Meraki with static IP. 

But I m not sure why is it jumping to another VLANs.