VLAN and DHCP conflicts. /renew and release only works temporarily [closed]

Solution 1:

DHCP requests get contained in the same broadcast domain as the client, so somehow your clients requests are reaching the Avaya DHCP server and its replies are being picked up before the Windows server.

DHCP requests and replies are broadcast so will be recieved by any device whatever IP address and subnet mask you have set.

It is not sufficient to have a different IP range - you need to properly segment your network so the Avaya phones and Windows clients. If your switches support it, you can achieve this with VLANs. If not you can do it old school with different switches and cables for phones and PCs.

And if that is not possible, you probably need to share the same IP subnet with PCs and computers, and have a single DHCP server in place configured to assign different settings according to some property of the client making the request.

But since you mention this started recently, most likely you have somehow bridged two VLANs or broadcast domains. This could be a switch (physical or virtual) that has ports connected on both VLANs or broadcast domains.

As other people have said, more info is really needed, but hopefully this has helped you narrow it down a bit.