SIP ALG on OpenWrt

We are facing issues with VoIP applications and we would like to know if OpenWRT uses SIP ALG by default.

I'm not sure about your problem, but this might be related:
[SOLVED] Incoming calls not reaching hosts on the network - #2 by vgaetera

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Thank you, but not related, really.

VoIP provider says that we should disable SIP ALG in any form, they say that usually routers does have this enabled. Doesn't seem to be an OpenWRT feature.

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the conntrack helper is a kind of sip alg I believe, it opens certain ports on the basis of reading the SIP messages. make sure you don't have the


package installed. If you don't then that's as far as you need to chase it I think.

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No exact match. Only the following ones:

iptables-mod-conntrack-extra (wouldn't be this one?)

If it is one of those, how disable SIP-ALG without breaking any other feature?

Could you describe the problem itself in detail?

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Calls are muted or "Service Unavailable". Other VoIP providers doesn't have any issues.

We only do calls, we don't receive.

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One way or two way?

Also do you have a public IP or are you behind CG Nat?


Muted both ways. We succesfully called the same numbers using another VoIP provider.

public, fixed IP. No problems using other VoIP providers (in addition to those that normally arise, such as difficulties in calling certain countries).

Hmm... usually this means your SIP provider is trying to do some shenanigans to get around NAT and their shenanigans are not compatible with some other shenanigans that someone else is doing.

What device are you using as your SIP endpoint?

It might be worthwhile to tcpdump on your WAN port to see what kinds of packets are arriving. The audio will be udp. so you could do:

tcpdump -i eth1 udp

if your wan uses eth1 for example.

then make a call, and look for whether the traffic is actually flowing, and which ports its on


As SIP endpoint we are using MicroSIP.

Make sure to configure the Windows firewall properly.

We need clarification on this.

There will be newer versions of OpenWRT not being affected by this?
Do we need to change/remove any package from our current OpenWRT setups?

The thread I linked was quite extensive. The wording of your statements seem as if you didn't read it. Also, the SIP ALG thing is not OpenWrt-specific.

The thread also noted there's no issues with default OpenWrt as it's not installed.

I've made no statements, just questions to be sure of - better safe than sorry.

In depth, there's no SIP ALG by default on OpenWRT.

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hello friends, I don't quite understand what is happening in my router but I think it is related to ALG. The problem is that the PUBG game does not work voice communication. it seems to use some kind of sip voip server and maybe the router is blocking it. I have a r7800 with the final 19.07.8. I have tried all the images (kong, nss, 21.02, etc) and the problem persists. If I use my 1043nd or the mobile connection via wifi and 4g, everything works correctly. in my case I would want to activate the alg, I think. the packages mentioned are not showing up on my router