modem-issues - VORADIAN | Business Telecommunications Service

There are certainly devices in the market that can and will cause problems, we have not yet discovered. So please do not use this list as a definitive guide and assume that any device not listed here is therefore endorsed.

ALG setting is one of the biggest issues with routers and is an industry wide problem. We are including an explanation that we found to be concise in explaining the problem from the VOIP-Info website.

(Excerpt from: VoIP-Info.org)

(End of excerpt)

In working with customer location issues, we have found the following routers to have major issues. This list should not be taken to be definitive, but only representative of devices our customers actually had in place and the resolutions taken. We've also noted if a router/modem is running DOCSIS 2.0 vs 3.0, and we have attempted to note which modems are running the 2.0 version. However, manufactures are known to change firmware and its requirements without notice. The older modem versions does not support higher bandwidth usage that is required with multiple (usually greater than 4 simultaneous) concurrent calls.

Problems: These devices running DOCSIS 2.0 have limited bandwidth support; if more than four simultaneous calls are connected, it discards packets, causing audio issues.

Correction: Change to a modem running DOCSIS version 3.0 as it has greater bandwidth support.

Problems: This firewall is known to intermittently allow phantom calls even when the port forwarding is locked down to a particular source address or range.

Correction: Change to a business class firewall with the necessary features.

Problems: The home version with wireless gets used by Comcast to also support their open Wi-Fi network (Hotspot) and this can lead to over utilization and voice quality issues. It is reported that it can be disabled, instructions are here  http://bgr.com/2014/06/11/how-to-disable-comcast-xfinity-wi-fi-hotspot/.  If this does not work then a call to ComCast customer service is needed.

Correction: Change to Comcast business version.

Problems: SIP ALG is enabled by default; the router stops passing the audio packets after 10 seconds of connection, reporting that the port is not available.

Correction: Change to a business class firewall with the necessary features.

Problems: EdgeMarc routers have problems supporting transfer, providing pass through when acting as proxy and the SIP ALG whether off or on (which requires separate licensing) does not function correctly. Older firmware versions have less problems than the newer.

Correction: Change to a business class firewall with the necessary features.

Problems: Usually leads to audio problems (used by Time Warner). The problem with this one is that under high utilization it starts buffering (or even freezing) packet output and there doesn't appear to be a way to set QOS to still allow RTP, so will eventually end up with voice quality issues.

Correction: Change to a business class firewall with the necessary features.

Problems: SIP ALG is enabled by default and cannot be disabled, even by Comcast support.

Correction: Configure the modem to be in bridge mode (Comcast may need to do this) and use a business class firewall behind it to perform QOS functions.

Problems: frequently used by Time Warner; intermittently causes loss of audio.  Per a Time Warner engineer, there is a cache that crashes and then stops RTP from passing through.

Correction: Change to a modem with the necessary features.

Motorola - SBG6580 - (SurfBoard Extreme Wireless Cable Modem Gateway)

No Registration possible behind NAT as the device changes Call-ID and causes the responses to be discarded by SIP clients/ATAs

No Solution at this time (SIP ALG, called SIP Pass Through, can not be disabled) .

Must disable NAT and put the device in bridge mode (check Motorola website for guide).

SpeedTouch - ST560 v6 (firmware >= 5.4.0.13 comes with SIP ALG enabled by default.) NAT type: symmetrical

Issues: No incoming calls. It replaces the private IP appearing in SIP headers with the public IP using a dumb text replacement. If for example the private IP appears in the "Call-ID" it replaces it too (that it's completely unnecessary).

To disable SIP ALG: ~# telnet router -> connection unbind application=SIP port=5060 -> save all

Zyxel - 660 family comes with SIPAL Genabed by default. NAT type: symmetrical

Issues: No incoming calls. SIP protocol broken making 50% of outgoing calls impossible because the wrong values are inserted into SIP headers.

To disable SIP ALG: ~# telnet router

Menu option "24. System Maintenance".

Menu option "8. Command Interpreter Mode".

ip nat service sip active 0

Netgear - WGR614v9 Wireless-G Router, DGN2000 Wireless-N ADSL2+ Modem Router

Firmware V1.0.18_8.0.9NA

To disable SIP ALG: From Wan Setup Menu, NAT Filtering, uncheck the box next to "Disable SIP ALG"

SMC - ToDo - NAT type: No symmetrical

Issues: The ALG doesn't replace the private address in "Call-ID" header (that is correct) but it does replace the "call-id" value in "Refer-To" header so SIP transfer is broken.

To disable SIP ALG: ToDo no ALG related options found via web and telnet. No idea of how to disable it.

Linksys - WRV200, WRT610N. NAT type: Symmetrical

Issues: The ALG replaces the private address in "Call-ID" header (not needed at all). Some phones (as Linksys with latest firmware) encode the "Call-ID" value in the "Refer-To" header (by escaping the dots) so the private IP appearing there is not replaced with the public IP. This causes that the call transfer fails since the proxy/PBX/endpoint will not recognize the dialog info.

To disable SIP ALG on WRV200; no ALG related options found via web and telnet. No idea of how to disable it.

To disable SIP ALG on WRT610N: Web Interface: Administration, Management, under side heading 'Advanced Features' SIP ALG, can be disabled.

Fortinet - All models come with SIP Helper enabled by default

To disable SIP helper: ~# telnet firewall

config system settings

set sip-helper disable

set sip-nat-trace disable

end

config system session-helper

show <---- use this to find out which entry is configured for typically 12 or 13

delete 12

end                                          

For SIP Trunks

 *If using Virtual IPs under objects make sure to turn OFF NAT within each IPv4 rule for VoIP. If not using Virtual IPs under objects make sure to turn ON NAT under each IPv4 rule for VoIP.

The preferred solution is to configure the SIP ALG. Policies that use the SIP ALG will not use SIP helper. Full documentation at http://docs.fortinet.com then pick FortiOS for the version on your device, then VoIP solutions: SIP.

Cisco - 800 series

To disable the NAT services for SIP in IOS, just run these commands:

no ip nat service sip tcp port 5060

no ip nat service sip udp port 5060

Juniper/Netscreen - SSG Series To disable SIP ALG:

In the Web interface: Security -> ALG

Asus RT-AC66U - Firmware enables their SIP ALG by default, previously it was not possible to disable from the GUI interface. With the latest firmware (as of 3/15/16) there is now a way to disable via the interface, Asus refers to this as SIP Pass-through. Un-checking the box for the feature will disable it. Attached below is a screen capture of the GUI page.

Comcast DPC3939B - has ALG pre-installed and cannot be turned off. (contact Comcast tech support to see if they can turnthis off).

Comcast Netgear Gateway Model CG3000 DCR -  will not allow customer to disable SIP ALG. The only true way to work around this is to place the CG3000 into bridge mode and then place a router/firewall behind it. *(note, we have seen sites that made this change and still encountered issues, suspicion is that it does not function in a true bridge mode. Some sites had to replace with a regular modem. Contact Comcast tech support to see if they can disable ALG remotely)

Arris TG862G and TG862G-CT - SIP ALG is enabled and no way to disable. These are often used by Comcast as a Gateway.

AT&T Uverse Arris NVG589 - SIP ALG is enabled by default and cannot be disabled. By default it will not support hosted phones, AT&T may be able to open port 5060 for SIP traffic but it is reported to us that it is not possible for user level admin to do so.

ACTIONTEC model GT784WNV - Frequently used by Verizon. The owners manual states that ALG is assigned automatically and there is no mention of a way to disable.

Verizon FiOS G1100 - This modem has SIP ALG enabled by default and Verizon has not provided a method to disable this feature. Verizon has also not released if it can be disabled by Verizon itself. Best recommendation at this time is not to use this modem.