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Routers with Known Issues

Routers with Known Issues

Overview

The following list covers routers, modems, and gateways that are known to cause problems with VoIP systems. This list is not exhaustive but represents documented issues and the available resolutions where they exist. If you are experiencing call quality or registration problems, checking this list against the equipment on the customer’s network is a useful early step.

Routers That Should Be Replaced

The following devices are confirmed to be problematic and should be replaced rather than worked around:

  • Frontier Sagemcom FWR226e (Fast 5290): When a second RTP stream is established, the first stream loses inbound packets. No known setting resolves this. Works only when a single phone is installed. Frontier ships this as the default router for 1Gb+ circuits in some regions.
  • Comcast Home Version with Wireless: The home version is also used by Comcast to support their open Xfinity Wi-Fi hotspot network, which can cause overutilization and voice quality issues. Switch to the Comcast Business version. Disabling the hotspot feature may help but is not always effective.
  • Motorola SBG-650: Used by Time Warner. Under high load it buffers or freezes packet output and does not support QoS settings that would allow RTP traffic to be prioritized, resulting in voice quality issues.
  • D-Link DIR-655: SIP ALG is enabled by default, and the router stops passing audio packets after 10 seconds of a connected call.
  • Ubee Modem/Router: Used by Time Warner. A cache crash causes RTP traffic to stop passing. Reported by Time Warner engineers.
  • Arris Modem/Gateway (DOCSIS 2.0): Limited bandwidth support means more than four simultaneous calls causes packet discard and audio problems. DOCSIS 3.0 versions support up to 16 calls.
  • Amped Titan HighPower AC1900: SIP ALG is enabled by default and cannot be disabled.

Routers with SIP ALG Enabled by Default

The following devices have SIP ALG enabled by default and require manual intervention to disable it. Instructions are provided where available.

  • Motorola SBG6580: SIP ALG (called SIP Pass Through) cannot be disabled. NAT must be disabled and the device placed in bridge mode.
  • SpeedTouch ST560 v6 (firmware 5.4.0.13 and above): To disable, telnet into the router and run: connection unbind application=SIP port=5060 then saveall.
  • Zyxel 660 family: To disable, telnet into the router, go to System Maintenance then Command Interpreter Mode, and run: ip nat service sip active 0.
  • Netgear WGR614v9 and DGN2000: Go to WAN Setup and uncheck the Disable SIP ALG box under NAT Filtering.
  • Netgear N600 (WNDR3400): Go to Settings, Advanced, Setup, WAN Setup. Disable ALG and enable IGMP.
  • Linksys WRT610N: Go to Administration, Management, and disable SIP ALG under Advanced Features.
  • Fortinet (all models): Telnet into the firewall and run the following commands to disable SIP Helper: config system settings / set sip-helper disable / set sip-nat-trace disable / end. Then remove the SIP session helper entry. If using Virtual IPs, turn off NAT within each IPv4 VoIP rule.
  • Cisco 800 series: Run: no ip nat service sip tcp port 5060 and no ip nat service sip udp port 5060.
  • Juniper/Netscreen SSG series: Disable via the web interface under Security, then ALG.
  • Asus RT-AC66U: No GUI option. Telnet into the device and run: nvram set nf_sip=0, then nvram commit and reboot. On newer firmware, go to Advanced Settings, WAN, NAT Pass Through, and set SIP Pass Through to Disable.
  • Comcast DPC3939B: ALG is pre-installed and cannot be disabled.
  • Comcast Netgear Gateway CG3000 DCR: SIP ALG cannot be disabled. Place in bridge mode with a router behind it, though true bridge mode behavior has been inconsistent on some units.
  • Arris TG862G and TG862G-CT: SIP ALG is enabled and cannot be disabled. Often deployed by Comcast as a gateway.
  • Arris DJ 2470: Intercepts SIP packets in bridge mode but works correctly when configured as a DMZ.
  • AT&T Uverse Arris NVG589: SIP ALG is enabled by default and cannot be disabled. Does not support hosted phones by default. AT&T may be able to open port 5060 but this is not always possible at the user level.
  • Actiontec GT784WNV: Used by Verizon. The manual confirms ALG is assigned automatically with no documented way to disable it.
  • Verizon FiOS G1100: SIP ALG is enabled by default and Verizon has not provided a method to disable it. This modem is not recommended for VoIP deployments.
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