While working on various things in a Asterisk VoIP deployment earlier I needed to override the DHCP NTP settings for a specific phone because this particular user was remote. The configuration file for their phone was actually using a different outbound proxy and SIP registration server address so they could operate remotely. One of the issues pointed out to me was the fact that the phone’s time was never correct and after some basic investigation I was able to locate the issue which is described below as well as how to override the DHCP NTP address settings via the Polycom SountPoint CFG (configuration) files.

Why Time Was Not Being Set For This Specific Polycom SoundPoint Phone:

All of the internal users were obtaining DHCP which included a NTP server address. The issue was that the remote user was first connecting via VPN and then receiving DHCP from a different location and a different subnet. The issue here was the fact that the DHCP the remote SoundPoint phone was receiving did not include a NTP server address which is why a separate configuration file (CFG) needed to be created for this user to override the DHCP NTP server address and provide a NTP server that the user could reach.

Set NTP Server Address Via Polycom SoundPoint Configuration Files:

Settings the time via the SIP configuration files for the Polycom SoundPoint phones is fairly easy by modifying the SNTP settings located in the sip.cfg or similarly named file. There is a section of settings underneath the TCP_IP section of the sip.cfg file that will begin with SNTP as shown in the below example.

Example SNTP Settings To Modify Polycom SoundPoint NTP Server:

      <SNTP tcpIpApp.sntp.resyncPeriod="86400"

Most of the above items will be set already and do not need to be changed however the four that relate to modifying the NTP server for the phones using this configuration file are noted below.

NTP Server Address For Polycom SoundPoint Phones:


The setting above will set the new NTP server address.

NTP Server Address For Polycom SoundPoint Phones:


This setting (if set to 1) tells the phone to ignore the NTP server provided by DHCP if it is actually provided by DHCP. In my case the external phone was not getting a NTP server anyhow.

NTP Server Address For Polycom SoundPoint Phones:


The gmtOffset setting will tell the phone what to set the time to. The -18000 above will set a phone to EST (Eastern Standard Time) for cities such as Louisville.

NTP Server Address For Polycom SoundPoint Phones:


The gmtOffset.overrideDHCP setting will tell the phone to ignore the timezone set via DHCP if it actually is set via DHCP.

Extra Notes Regarding Multiple Configuration Files For Polycom SoundPoint Phones:

In the example I noted in the beginning of this article regarding internal and external phones I ended up having to tell the external phones to pick up a new sip.cfg that included the above settings. If you are in the same scenario simply copy the original sip.cfg to something else like sip_ext.cfg and then specify the phone’s configuration file to pick up the different config. Typically phone configuration files are MACADDRESS.cfg or something like 01234567890AB.cfg.

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