Audio distorted during SIP call using Asterisk behind NAT

I have an Asterisk server (11.25.1) which is running in VM. Initially I had configured only private static IP to this server and later I have configured public IP to this server. What I need is client behind NAT is also is able to access this server. So that only I have configured public IP. Everything seems to be good in local internet. But while using public internet like mobile data, audio is not hearing properly from public IP to local IP. But vice versa is working fine (local to public IP).

Local internet - Local internet :working fine
Local internet - Public internet :working fine
Public internet - Local internet :Noisy audio
Public internet - Public internet :Noisy audio

Port configurations (TCP & UDP) :
SIP -5060
RTP -10000 to 20000
The above ports are opened in both public and private IP.

sip.conf :
nat=force_rport,comedia
externip=
localnet=/255.255.255.0

I have tried with all codecs. But I can’t able to trace out this issue. Please help to me fix this issue.

What does “sip show channelstats” say?

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check upload or download! is there something saturating the network >?

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Hi @EkFudrek,

Thanks for the reply.
I have checked " sip show channelstats " during call .It shows that some packets are lost from public IP configured device.

Hi @benphone,

Thanks for the response.

How to check this staturation?

The next question is about the reasons, but at first one probably has to look outside Asterisk.

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@EkFudrek. I don’t know how to debug this audio issue. Kindly suggest me some ideas to debug this one.

The lost packets tell you you have some sort of network saturation. The rest of the problem is a network one, not a VoIP one.

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Hi @david551,

Thanks for the response.

How to debug and resolve this network saturation problem?

Hire someone who understands TCP/IP networks.

You need a lot more information about your environment than you are likely to be able to provide here.

If the traffic is going out over a public network, you may need to change your internet service provider, or upgrade the product you are using.

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@david551

Thanks for the response.

Is it possible to trace the network saturation using wireshark?

wireshark might be one tool use, but you might not be able to install it in the right places. with modern network promiscuous mode isn’t as useful as it was on coaxial type ethernet.

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Thanks for the reply @david551 .