Hi,
I had changed the network on a DHCP pool and the pool in not giving addresses. When I debug on the Cisco 2921 i see the following output:
000188: Jan 24 2018 12:35:28.223 EET: DHCPD: Sending notification of DISCOVER:000189: Jan 24 2018 12:35:...
No more than 10 IP Phones. At this point the phones are with static IP addresses from that pool and everything works. If I use the scan no one will reply from the old network.
The IP Phones are taking their IP addresses dynamically from the pool. After I changed the network in the pool I did factory reset on the phones but didn't helped, also. There are no conflicts... it is very strange. The router is without support, so ...