SIP ALG

[Authority]

My VoIP vendor swears up and down that all the problems we are having are caused by SIP ALG not being disabled in my router. While it definitely is turned off I am wondering if it's possible that the switch is broken, that i just think it's off but it really isn't.

Is there anyway to confirm that SIP ALG is really off, like any kind of test? Of does anyone know if it's a known issue or anything?

 

[pete y testing]

strange that you even need to disable sip alg as i have a voip phone here behind an asus and it works without issue and registers every time

what devices is the asus connected to as far as internet is concerned as it may be a dual nat issue

 

[Authority]

Thanks for the reply - no dual NAT, the modem is bridged. I have about 25 users on some pretty snazzy phones but we have issues park/pickup and the occasional device freeze/reboot that the vendor says they only see when SIP ALG is enabled. It might be in the switch, I plan to do a factory reset of it tomorrow, but I'd really like to rule out my beloved Asus router.

 

[Authority]

Does anyone think QoS could in any way break SIP?

 

[sfx2000]

SIP-ALG can work with some providers, and break with others -- toggle the setting and see what works...

It's not just Asus - happens to other vendors as well, and it's mostly due to SIP being application layer, and routers don't generally work at that layer - and SIP-ALG is kind of a hack as a result...

 

[RMerlin]

Is there anyway to confirm that SIP ALG is really off, like any kind of test?

lsmod | grep nf_nat_sip

If the module isn't loaded, then it's definitely not enabled. The webui settings is working properly.

 

[Authority]

lsmod | grep nf_nat_sip

If the module isn't loaded, then it's definitely not enabled. The webui settings is working properly.

In reading your other threads on this matter... specifically this one, I am unclear of the CURRENT status of this feature.

Here's what I think I understand for "SIP Passthrough"

Enabled: Allows traffic but doesn't modify. This should be safe right?

Disabled: Doesn't allow traffic. This is what I was using, and it still works which is puzzling.

"Enabled w/ NAT -Helper" <--- ALG?

So when my provider says "disable ALG" that means I can have SIP Passthrough "enabled" just no "nat-hlepers"?

Is that right?

I'm chasing random reboots here, and frankly I haven't noticed a difference with ANY setting, but for troubleshooting I really need to understand what these sort of vague settings actually mean. Thanks.

 

[RMerlin]

Yes, NAT Helper = ALG here.

 

[sfx2000]

One thing that might not have been considered is if the ISP is nat'ting, or even more insidious is the Carrier Grade NAT's that have popped up lately...

 

[Authority]

One thing that might not have been considered is if the ISP is nat'ting, or even more insidious is the Carrier Grade NAT's that have popped up lately...

My modem is bridged and the IP is 50.x.x.x so I don't think it's NAT'd?

 

[matthew johnson]

If you dont have voip should sip be disabled? Would it effect gaming?

 

[RMerlin]

If you dont have voip should sip be disabled? Would it effect gaming?

That setting will have zero effect on performance.

 

[Authority]

If you dont have voip should sip be disabled? Would it effect gaming?

Merlin said that there is (bizarrely) no difference between "enabled" and "disabled", so I guess there would be no effect on gaming.

Could def be more clear.