One-way audio / no sound during calls (SIP ALG)

Modified on Mon, 3 Oct, 2022 at 4:33 PM

If you experience lost calls or one-way audio on your phone system (ie, one party can hear the other, but the other party doesn't have audio), the problem is likely caused by the SIP ALG option enabled on the router.

The SIP ALG function is available and active in most routers, but it negatively affects the operation of the call center, e.g.:

- One-way sound (one party hears the other, but the sound does not work the other way around),

- The phone doesn't ring

- When you pick up the phone, the call is disconnected

- The call goes straight to voicemail for no reason

Deactivating the SIP ALG option:

The SIP ALG option must be searched for directly in the router's settings, and it must also be turned off here, for this:

1. Open the router admin interface in your browser and log in with the correct username and password.

2. Navigate to the appropriate menu item and turn off the service

3. Save the settings and restart the router (if the restart did not happen automatically)

The figure below illustrates where the SIP ALG setting is located for TP-Link routers. Below the figure you can even find how to turn off the option for some of the more popular models.

Example Showing How to Turn Off SIP Application Layer Gateway (TP-Link)

Router type

Deactivating the SIP ALG


  1. Select Advanced and then accept the warning by clicking Yes.
  2. To disable SIP ALG, uncheck the corresponding box.
  3. Click the Apply button.
  4. Select Advanced, then accept the warning by clicking Yes, then click  Remote Administration.
  5. Select the Allow Incoming WAN ICMP Echo Requests checkbox and click Apply.


  1. Under the Firewall menu item, select Firewall / ACLs.
  2. Click on the ALG Settings menu item.
  3. Uncheck the box next to SIP ALG.
  4. Click the Apply button.

If you work from the command line (terminal), use the following command:
no ip firewall alg sip


For most Arris broadband gateways:

  1. Open the IP address of the gateway (
     Username: admin Password: motorola
  2. Open Advanced and then Options.
  3. Uncheck SIP.
  4. Click Apply.

Arris BGW210

  1. Enter the following address in your browser:
     Log in without a username and use the password on the sticker on the device.
  2. Within the Firewall section, click Advanced Firewall.
  3. Turn off the SIP ALG option.
  4. Turn off the Authentication Header Forwarding option.
  5. Turn off the ESP Header Forwarding option.
  6. Click the Save button.


  1. Within the Advanced Settings section, click WAN.
  2. Click the NAT Passthrough tab.
  3. Set SIP Passthrough to “Disable”.
  4. Click Apply.


U-Verse Pace 5268AC gateway
 The SIP ALG option cannot be disabled for this broadband gateway. We recommend that you use the gateway only as a modem, not as a router. Get a router that can turn off SIP ALG.


Cisco general and enterprise solutions:
no ip nat service sip tcp port 5060
no ip nat service sip udp port 5060

Cisco PIX routers:
no fixup protocol sip 5060
no fixup protocol sip udp 5060

Cisco ASA routers:
Find 'Class inspection_default' under 'Policy-map global_policy' and run the following command: no inspect sip


  1. Click Advanced Settings.
  2. Locate the Application Level Gateway (ALG) Configuration section.
  3. Uncheck SIP.
  4. Click Save.


  1. Click Advanced at the top.
  2. Click Firewall Settings on the left side of the screen.
  3. Uncheck Enable SPI.
  4. Set the UDP and TCP Endpoint Filtering options to Endpoint Independent  in both cases .
  5. Uncheck SIP in the Application Level Gateway Configuration section.
  6. Click the Save button.


  1. Use the following commands in the CLI:
    config system session-helper
     show system session-helper
  2. Find your SIP session ID (typically #12)
  3. Delete #12 or the value shown instead
  4. Confirm the deletion with the following command:
     show system session-helper


Linksys Smart Wi-Fi (E Series):

  1. On the left side of the screen, click Connectivity.
  2. Click on the Administration tab.
  3. Within the Application Layer Gateway section, check that there is no check mark next to SIP.
  4. Click Apply or Save.

Previous Linksys models:

  1. On the Admin page, find the 'Advanced' section.
  2. Turn off SIP ALG.

Linksys BEFSR41 routers:

  1. On the Admin page, click Applications and Gaming.
  2. Click on the Port Triggering option. 
  3. For the application name, enter 'TCP'.
  4. For 'Triggering Range' and 'Forwarded Range', enter "5060" in the Start Port and End Port fields.
  5. Click 'Enable'.
  6. Click Save and Reboot.


In the case of Mikrotik routers, the SIP ALG option is called: SIP Helper.

  1. Use the winbox software to set it up.
  2. Open IP and then Firewall.
  3. Click on Service Ports tab and disable via GUI.
  4. If you are using a command line (terminal), enter the following command:
    /ip firewall service-port disable sip


Netgear routers with Genie interface:

  1. Select the Advanced tab at the top.
  2. Open the Setup menu on the left side of the screen.
  3. Click the WAN Setup menu item.
  4. Check "Disable SIP ALG".

Other Netgear routers:

  1. Under the Security/Firewall section, click Advanced Settings.
  2. Disable the SIP ALG option.
  3. Find the Session Limit option under the Security/Firewall section.
  4. Increase the UDP timeout to 300 seconds.


  1. In the System Setup menu on the left, click VoIP.
  2. Check the 'Enable Consistent NAT' option.
  3. Uncheck 'Enable SIP Transformations'.
  4. Click the Accept button.
  5. To increase the UDP timeout, open the Firewall Settings menu item and then the Flood Protection option.
  6. Click on the UDP header and increase the UDP connection timeout value to 300 seconds.
  7. Click Accept to save.


Newer TP-Link routers (Archer series):

  1. Click on the Advanced tab.
  2. Open the NAT Forwarding menu on the left side of the screen.
  3. Uncheck SIP ALG, RTSP ALG and H323 ALG.
  4. Click the Save button.

Previous TP-Link routers:

  1. Use the Telnet client from the command line.
  2. Issue the following command:
     ip nat service sip sw off


  1. Click Advanced and then Options.
  2. Uncheck SIP and RTSP.
  3. Click the Apply button.


UniFi Security Gateway

  1. Log in to the UniFi security gateway.
  2. Click Routing & Firewall on the left
  3. Click on the Firewall tab at the top and select the Settings submenu.
  4. Turn off the Toggle H.323 and SIP options.
  5. Click the Apply Changes button.

Edge Routers (ER-x)

  1. Open the router's administration interface (usually
  2. Use Config Tree or command line to disable SIP ALG.

Config Tree:

  1. Select the config tree in the upper right corner.
  2. Open system, conntrack, modules, and sip.
  3. Mark the disable option with a + sign.
  4. Click the Preview option.
  5. Click the Apply button.

Command Line Interface:

  1. In the upper right corner of the administrative interface, select CLI.
  2. You can also change the UDP timeout option there.
  3. Enter the following commands:
    set system conntrack modules sip disable
    set system conntrack timeout udp stream 300
    set system conntrack timeout udp other 300

Verizon FiOS


The SIP ALG option cannot be turned off for this broadband gateway. We recommend that you use the gateway only as a modem, not as a router. Get a router that can turn off SIP ALG. 



  1. Click Configuration and open the Network settings section.
  2. Click on ALG on the left.
  3. Check the boxes on the right:
    1. Uncheck Enable SIP ALG.
    2. Uncheck   Enable SIP Transformations.
  4. Click the Apply button.

ZyXEL C1000Z/C1100Z (CenturyLink):

  1. Click Advanced Setup.
  2. Click on the SIP ALG option on the left.
  3. Set SIP ALG to Disable.
  4. Click the Apply button.

ZyXEL P600:

  1. Use Telnet to log in to the router ( and enter the password.
  2. The default password is 1234. 
  3. Type the value below “24” and press enter.
  4. Then the following: “8” and press enter again.
  5. Type the following command:
    ip nat service sip active 0
  6. Press enter when done.

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