DPC3941B sip alg?

Hello KSB and welcome,

If you are running DPC3941 Firmware Version 1.7.3 then your SIP Alg should be disabled by default.

Hope this helps you out.

Thank You. 

There is no specific sip alg disablement parameter within the DPC39XX Comcast Gateways (CG) GUI Interface. This is default handled within the CG FW. However, if you need any related sip alg ports opened on any Routable Static IP device that facilitates VOIP SIP, you can certainly open the ports within the Advanced,True Static IP Management facility.

Hi Wright and welcome to the business forums. 

I appreciate you reaching out about SIP ALG. SIP ALG is now disabled on all Comcast Business leased modems by default. What exactly going with your VOIP?

Can you tell me if our firmware has SIP ALG disabled?  I am not sure of the firmware version.

Our DPC3941B has a hardware revision of 1.1 and a software version dpc3941b-v303r20421753-170721a-CMCST.p7b

Can we get an upgrade of the firmware that will help our VOIP issues.

We are experiencing issues with our voip phones and our voip provider has recommended turning off SIP ALG as well as all NAT functions on the router.  They initially suggested bridge mode, but we have a public address block from Comcast, and cannot use bridge mode.

When we moved into our current location there were issues with the modem provided and they may have given us an older modem as they thought it was more reliable.

Could you elaborate on your VOIP issues? I'll be glad to assist. 

I would like to review for any issues that may be causing that with your internet services. If no issue is found, you may need to speak with your VOIP provider again to look into this.

May I please have you private message me your full name, the name of your business, the full address of your business location and the phone number associated with your business account?

Our main voip issue is incoming calls sometimes do not cause the ip phone to ring, but roll to a forwarded cell phone, or go directly to voice mail. Outgoing calls work fine.

Was there ever any resolution to this?

We recently switched over to Comcast Business internet and we are haveing customers report voice issues since the transition.  They contacted thier VoiP provider and they said the same thing the prvious post said " voip provider has recommended turning off SIP ALG as well as all NAT functions on the router"  Customers are reporting that since the transition, they have trouble hearing the caller.  Let me know if there is a solution.

Thanks,

Mark

Hi michalskim and welcome to the forums. I appreciate you letting us know about the trouble; is your device rented from us or owned? The post above from Comcast_Phil would be the solution since SIP ALG would be disabled on all our rental gateways by default now. 

I don't think that rented/owned applies here.  The Comcast business device is a Juniper router (owned by Comcast) in a data center that has a 10GB cross connect to our router (in a different rack) in the data center.  Customer started to get reports of VoiP quality issues after we transitioned to Comcast business internet after 6/24/2019.  We have SIP ALG disabled on our firewall and have not made any changes to NAT for these customers.  When the customer engaged the VoiP provider, they asked about the SIP ALG being enabled and to check on NAT configuration.  Again, we have made no changes to this configuration on our end. 

I would be happy to provide you with our information so you can confirm that the Comcast owned Juniper router is configured in a way to cause these issues.  Let me know.

Thank you.

Good morning, michalskim.

The Juniper router provided for Metro E services will not block Session Initiation Protocol (SIP) Application Layer Gateway (ALG). If your VOIP is configured not to have their Cisco Firewall be the "Gateway", and transport that via ethernet to a 3rd party provider, you will need to ensure that the Firewall is "forwarding" that request.