It get private IP address from ONT

AIUI VOIP equipment if problematic if you are behind CGNAT.

But as you have IPV6:

The Cisco SPA 191 supports IPV6.

This should connect to a VOIP provider such as A&A that supports IPV6. Connect the N300 to the phone port on the SPA 191,

They use CGNAT unfortunately would STUN help with the issue I am having

STUN enabled: Yes No
STUN server address:

STUN server port:
3478
STUN refresh time:
240
sec
NAT refresh time:
20
sec
Outbound proxy mode:

Whilst I don’t profess to understand the finer points of this thread (there are much more learned people on the scene) I wonder whether AAISP L2TP service might provide a possible solution to the apparent CGNAT issue.

They appear to offer a very modestly charged version (Light) specifically aimed at the VOIP/CGNAT problem.

See Here

Of course there is still the issue of establishing the outbound L2TP connection which depending on the OP experience (and availability of kit) may be an issue

So the OP is up against two instances of NAT, one in the router at home and another CGNAT at the provider. I have some doubt that you can get VoIP to work reliably in such a situation. So, the options are:

1) get a static IPv4 address from your broadband provider

2) check whether your router supports VPN termination and then set up a VPN (there are providers that offer free trials), ideally one with a static IPv4 address. (Note that you may not be able to watch BBC over the Internet any more if the VPN server hands out a non-UK IP address)

3) investigate IPv6: I don't know whether the Gugaset supports IPv6, but if it does, this may be the cheapest option.

Heavily snipped

In reply to a post by essex_man:

2) check whether your router supports VPN termination and then set up a VPN (there are providers that offer free trials), ideally one with a static IPv4 address. (Note that you may not be able to watch BBC over the Internet any more if the VPN server hands out a non-UK IP address)

At the risk of going a little off (immediate) topic, whilst it is a steep learning curve (and in my case not withstanding years of usage continues to be so) this aspect of multiple interface routing and utilising VPN’s was one of the reasons I went down the pfsense route.

Download here

Certainly not a quick fix, but as a longer term solution for the OP I would recommend it - just about anything is possible with pfsense.

As to the existing router, this presumably could be re provisioned as a WiFi access point connected to the local network, so no loss of WiFi functionality, albeit there would be the expense of additional hardware to host pfsense.

In reply to a post by essex_man:

So the OP is up against two instances of NAT, one in the router at home and another CGNAT at the provider. I have some doubt that you can get VoIP to work reliably in such a situation...

I've run exactly this configuration with Voipfone through a HT801 ATA for the last 18 months without any problems. The HT801 was pre-configured by Voipfone and it just works, so I don't claim any credit for this. But it can be done.

Mine did the same. Gave up on it in the end. I had to switch between dynamic and static ip to force it to go and re-register.

Got a Yealink now. It does the same thing but the internet has to be off for longer. It picks up some stupid IP address instead of the static one allocated by the router. I have now set that to manual as well. STUN seems to help with call quality issues but not this. I haven't tested it with manual everything yet as there's only just been an Internet outage long enough to trigger it.


I have concluded VOIP isn't very robust. I had vonage for years and that was flakey a lot too.

Only other thing I can think of is to find if there's a specific number of retries before it gives up trying to re-register and increase that number to a much larger amount so that smaller outages don't bother it.

If a reboot always fixes yours then the lazy answer is to probably have one of those wifi plugs on it and reboot it that way. The tapo ones I have seem to be pretty tolerant of internet going away and coming back.

In reply to a post by serichards:

I have concluded VOIP isn't very robust. I had vonage for years and that was flakey a lot too.

I tend to disagree, I have been using VoIP for outbound calls on an ADSL2 broadband connection for 10+ years. Saved me £££ over POTS priices, especially when calling abroad. Just over a year ago, I ditched the copper landline, moved the broadband to Three and my ex-BT phone number(for inbound calls) to A&A.

There have been some occasional problems with interoperability between the SIP client and server, but copper landlines go down as well (diggers damaging cables, ripped dropwires etc.) so all in all VoIP has been serving us well and saving a lot of money.

Having said that, I made sure only to sign up to broadband services that provide a public (non-NAT) IPv4 address and a VoIP client built into the router (so the VoIP client is aware of any change in the public IP address and re-registers automatically).

I am amazed to read that FTTP broadband connections frequently go down, seen that a lot on our ADSL2 connection but one would have thought that optical fibre was more reliable. Even my 4G connection on Three stays up 24/7 and keeps the public IPv4 address for weeks.

I have heard that if I change transport type to TCP it will help for CGNAT. So I did try that but instead just stuck with registration failed until changed it back to automatic which is very weird which made it work with automatic transport type. This is the link: https://knowledge.crazytel.com.au/en/knowledgebase/a...

But it didn't help at all so don't know what to do.

Anyone got a solution please don't know anything else to do. Should I just change voip equipment and get like a Yealink or something I don't know. Been trying to contact broadband provider but no luck probably after new year's