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371 posts

Ultimate Geek
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Topic # 133633 28-Oct-2013 19:18
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Hi,
I have an issue with my Cisco SPA303 VoIP phone. It seems I can make outgoing calls fine but if I get an incoming call, the phone rings and I answer but there is silence - no voice coming through and apparently they cant hear me either. Is it a firewall issue? I did notice a setting for mapped SIP port per extension, should I be mapping these through my router? I'm asking before I do this because I have had these phones for a while and never had this issue before...

Thanks in advance

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Biddle Corp
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  Reply # 923194 28-Oct-2013 19:29
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Assuming it's not a codec issue in approximately 99.993% of cases lack of audio is a NAT issue typically caused by double NAT (which will break VoIP in most cases) or a SIP ALG.

You should never port forward a SIP port unless you understand the consequences, and the fact you've mentioned this suggests you don't. RTP traffic also isn't carried over the SIP port, it uses it's own ports.




371 posts

Ultimate Geek
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  Reply # 923195 28-Oct-2013 19:39
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sbiddle: Assuming it's not a codec issue in approximately 99.993% of cases lack of audio is a NAT issue typically caused by double NAT (which will break VoIP in most cases) or a SIP ALG.

You should never port forward a SIP port unless you understand the consequences, and the fact you've mentioned this suggests you don't. RTP traffic also isn't carried over the SIP port, it uses it's own ports.



Okay- I haven't forward anything because like I said I never have had to before, and it shouldn't be double NAT'd at all, just one level is bad enough thanks! 
Any suggestions based on this?

Thanks

 
 
 
 


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  Reply # 923196 28-Oct-2013 19:40
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Sounds exactly like an ALG screwing with SIP.

What make and model is your router? Pretty much all of the residential routers come with SIP ALG enabled by standard.



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Ultimate Geek
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  Reply # 923198 28-Oct-2013 19:42
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chevrolux: Sounds exactly like an ALG screwing with SIP.

What make and model is your router? Pretty much all of the residential routers come with SIP ALG enabled by standard.


Oh?
It's a TP-Link TD-W8960N -- fairly customisable if I remember correctly

Thanks

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  Reply # 923201 28-Oct-2013 19:51
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Ok cool.

For starters there is this post that seems to refer to a firmware issue with SIP ALG. So check you have the latest firmware.

After that have a nosey around in the NAT settings and you should find a place to turn ALG's on and off.

If you can't find anything in the WebUI then it looks like you might have to telnet in to it and do it that way. Top result in google gives this article on how to do that.



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Ultimate Geek
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  Reply # 923215 28-Oct-2013 20:08
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Awesome thanks for all that!!

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