Configuring the Arris DG1670A Modem

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 by 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.

There are four 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. SIP ALG is enabled by default on the Arris DG1670A, and while SIP ALG and DNS Proxy can be disabled, doing so does not always resolve audio quality issues.

ISP Controlled Device Management: The device is managed by the ISP, and neither you nor Nextiva are made aware of these changes. If the device is reset, the original issues will return.

UDP Session Integrity: When a call comes into a Call Group and simultaneously rings all phones, the Internet traffic of the internal network spikes. Without multicasting enabled, you can have what’s called “port collisions”. Basically, data coming into the network is sent out to all devices on the network. Since all phones are likely using port 5062, the data spike causes packets to be dropped. This can cause failed transfers, dead air upon call retrieval, among other issues.

DNS Proxying: 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


To Configure the DNS Server and Disable SIP ALG: 

  1. Log in to the Arris DG1670A by navigating to the router’s IP address (Default Gateway).
  2. Click LAN Setup.
  3. Place a check in the Enable DNS Override checkbox.
  4. Enter the following required information:
  • Primary DNS Server IP:
  • Secondary DNS Server IP:
  • DNS Relay: Disabled (unchecked).
  • If the Arris is your only router, NAT Mode should be set to RoutedWithNAT. If the router will need to be bridged, NAT Mode should be set to Bridged.
  1. Click Apply.
  2. Click on Firewall.
  3. Disable (uncheck) Ping Blocking.
  4. Click Apply.
  5. Back to the Firewall option, click ALG (if available).
  6. Uncheck SIP and click Apply. If this option is not available, Nextiva recommends putting this device into Bridge Mode with the assistance of your ISP. Once the device is bridged, Nextiva recommends connecting a router recommended by Nextiva.
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