Our Mitel phones get a DHCP address from DHCP on our Windows Server 2012R2 domain controller. We have a problem where dozens of the Mitel phones (though less than half of them) are showing an entry in DHCP of "Bad_Address". We have DNS scavenging enabled, DHCP conflict detection attempts are set to "2" and I cannot find any rogue DHCP servers on the network. I cannot figure out what is causing these Bad_Address entries and why it is only the Mitel phones that this happens to (not any of the PCs). Does anyone have any ideas as to what I can investigate? I have spent many hours googling this and found nothing that solves it. We initially thought this was caused by setting up a failover DHCP server last May but we took that down last May and this problem still persists many months later. We shortened the lease durations on the scopes where this happens from 8 days to 2 days and 3 days (we did that months ago) and that didn't help. We are not aware of any conflicts on our network causing the phones or PCs to have issues (so there are no symptoms of IP conflicts) except that in the last few weeks, a few of the phones will sometimes have no audio when making/receiving calls but that only persists for a few minutes. When that happened this afternoon to a phone, I looked it up in DHCP and saw that it had one of the Bad_Address entries.
