Configuring an Arris/Motorola DG860A

The ideal network involves your Internet Service Provider (ISP) connecting onsite to a stand-alone modem that connects to a router, preferably a router recommended to you from Nextiva. If you have more devices on your network than ports on your router, you can connect a switch to your router to expand the number of ports. If the instructions below do not resolve call quality issues, we recommend you purchase one of the recommended routers in the link above.

There are three main areas that you should be concerned with regarding your network. They are:

SIP ALG: Nextiva uses port 5062 to bypass SIP ALG, however, having this disabled is always recommended. SIP ALG inspects and modifies SIP traffic in unexpected ways causing one-way audio, deregistrations, random error messages when dialing and calls going to voicemail for no reason. Depending on the firmware version, this setting may not be able to be disabled.

DHCP: There are known software issues with the DHCP server on this device. It causes IP address release and renewals, which can cause Poly phones to deregister.

DNS Server Configuration: If the DNS server being used is not up to date and consistent, devices (Poly phones in particular) can become deregistered. Nextiva always recommends using the Google DNS servers of and


  1. Log into the Arris modem by navigating to the default gateway (IP address) of the router.
  2. Click the Firewall tab at the top of the page, then select Firewall Settings.
  3. Enter the following required information:
  • Firewall: Leave checked (enabled).
  • DoS Attack Protection Firewall: Leave checked (enabled).
  • Ping Blocking: Unchecked (disabled).
  • Block Fragmented IP Packets: Leave checked (enabled).
  • SIP: Unchecked (disable).


NOTE: If the setting SIP is not available, you will need to have your ISP upgrade to the gateway’s firmware to the latest version.


  1. If you own or will own Poly devices, click the LAN Setup tab.
  2. Enter the following required information:
  • Enable DNS Override: Enabled (checked).
  • Primary DNS IP:
  • Secondary DNS IP:
  • Enable DNS Relay: Unchecked (disabled).
  1. Scroll down to the bottom of the page and click Apply.
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