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I have some Polycom 550 phones I'm using and when I use DHCP, they will not pick up the time. The phone will reach our SIP server located in a different office without issue and the phone can make calls, but the time and date just blink and default to midnight and January.

Using DHCP, I can still set the DNS servers, DNS domain, NTP server, and Gateway manually and this still won't work.

When setting all of those things manually, essentially the only thing the phone is getting from the DHCP server is an IP and the Subnet.

However, once I disable DHCP and set the IP and Subnet manually (to the same exact IP and Subnet it was being assigned via DHCP) everything works properly.

Does anybody have any idea why this might be? It is easily fixed by setting the IPs manually on the phones but I'd like to be able to use DHCP.

Thanks in advance.

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The phone is possibly requesting an NTP server address from the DHCP server, which is not returned, returned but not valid, or returned but unreachable.

You could investigate this, or override it using the phone's config file, as described here.

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