3CX Failover & SIP Trunk configuration

[sdg]

Hello

In October we did a migration from our old PBX (SopServ) to 3CX.

Seeing as our provider (which is 3CX supported) from the very start with our old PBX has supplied us with an IP range for us to utilise (xxx.xxx.xxx.xxx/29), and that we could have a failover in place with 3CX by opting for the enterprise license, we were very excited to set this up.

So we setup two VM's (Windows Server 2019) each with two NIC's, one for our internal Voice VLAN, the other with an address from the IP range we can use from our providor for all SIP communication and setup the necessary permanent routes in Windows for the second NIC. Now during the test phase before the migration we discovered an issue with two-way audio when making calls to external numbers, that audio from the called external number did not reach the IP phone used to make the call. After some searching, testing and looking through packet captures we found the cause of the problem, and the solution was to provide the SIP NIC IP in the SIP Trunk settings
under SIP Trunk -> Options -> Select which IP to use in 'Contact' (SIP) and 'Connection' (SDP) fields, i'll attach a screenshot of this setting.

The issue we are now facing is that, when the backup runs and then the restore procedure happens on the passive failover server, it also copies that IP address from the SIP Trunk, which is not wanted as that address would not be reachable if a failover were to happen. We have also verified this, by keeping that IP during a failover, and as predicted we again have no two-way audio but in the opposite direction, which is a logical outcome as that IP address is not reachable.

Our supplier then suggested we contact our ISP / Voice provider to ask if they could let us register two IP addresses through DNS on their end on the router so we could instead use a FQDN in that SIP Trunk setting instead of an IP address, but our provider cannot do this for us.

So my question is, has anyone ever done a similar setup like this, with an IP registered based SIP Trunk, or does anyone have a solution to our problem so we could fully benefit from the current failover solution provided by 3CX?

If required i can provide additional information or screen captures of our setup.
I also still have a wide range of packet captures of all situations along with 3CX Generated Support Info during the tests we did by letting the failover happen.

Thank you in advance for your time and possible responses / solutions,
King regards,

Stefaan

 

[sdg]

Hello

Upon reading the sticky thread about information to provide i'll reply with some additional information seeing as i can't seem to find how to edit my original post.

• 3CX Version: Enterprise Annual - 16.0.3.676
• Server OS: Windows Server 2019 Standard - Fully up-to-date
• Is the 3CX Server Hosted and where: On Premise - Hyper-V Virtualisation
• Trunk Provider or Gateway Make/Model: SIP Trunk Provider - Destiny (Belgium)
• Has the Firewall Checker passed: YES

Kind regards,
Hoping for a response

 

[JohnS_3CX]

Hi Stefaan

It sounds like there are a lot of unnecessary things in your setup that may overly complicate your system without any benefit, only caveats. However, would you mind drawing up diagram (using fake IPs) so we can better understand your setup? I have a feeling it can be simplified and you can still have your failover.

 

[JohnS_3CX]

Meanwhile, some notes:

• sip2.mottovoip.nl has two IPs associated 91.236.192.231 & 91.212.215.228 so you have provider redundancy by using our default template which is FQDN-based registrar
• The audio issues you face on the IP phone are likely unrelated and should be resolved otherwise
• Two NICs are not necessary, this may resolve the audio issue by ditching one NIC to boot
• The failover server must have the same settings

I think a redesign needs to be considered in this case, unless there are other details we are not aware of.

 

[sdg]

Hi John

First of all, thank you for your responses.

I have done my best to clarify our setup a bit more in the attached PDF file.

While we did select the default SIP Trunk template, we use different IP addresses only for SIP Registration, which were given to us by our provider. Even though our provider is in some way or form (not entirely sure) associated with mottovoip, they gave us those specific IP addresses along with a FQDN option for us to use, but this isn't the source of the problem.

If desired i can upload all the packet captures i've made along with 3CX Generated Support Info and provide them to you via a WeTransfer link in PM's. These were made and generated by us on demand of our supplier.

As the PDF file indicates, we are working over an MPLS network, with 10 sites in 10 different locations throughout the country. The Voice VLAN is accessible across the entire network, the provider SIP VLAN is to my knowledge only accessible in the datacenter where our servers are. So i'm not entirely sure a single NIC setup would work. Apart from that we also like this setup since it keeps everything VoIP related separated from other traffic.

edit
Aside from that, if we were to only work with 1 NIC, and then i assume you mean the NIC with the SIP address, we would face an issue of not being able to provide our IP phones with addresses, since the SIP address range provided to us by our provider is a /29 range, so we only have 5 addresses available. and our MPLS network has 10 different ranges between the 10 different sites.

Regarding the audio issue, it is resolved if we add the NIC specific IP address to the trunk setting, but then our actual problem is with the failover procedure. When the passive server does the failover restore it copies the sip trunk settings made during the backup procedure on the primary server.

We don't think a setup like this with 2 NICs is unique and are still hoping for a solution that potentially doesn't involve uninstalling and reinstalling everything again while these systems are running in a production environment.

Kind regards

edit 2
I think our setup is most relatable to the setup displayed in the diagram on following webpage under "Multiple internet gateways" where we also have 2 NICs:

https://www.3cx.com/blog/docs/network-configurations-supported-3cx-phone-system/

Since most systems with failover / High-Availability have the ability to provide a Virtual IP that handles the HA, is this perhaps also possible to do with 3CX?

 

[sdg]

Hi @JohnS_3CX

I don't mean to push my luck but it would be nice and appreciated to have a potential answer on our situation.

Our supplier, whom is a Platinum Partner, did guarantee us that a failover with our setup was possible, but now we're being thrown from one camp to another.

Kind regards

 

[JohnS_3CX]

Hi,

Currently what you need cannot be done, but we are planning to make some improvements in the way failover works in the future that I think you will benefit from. The changes will first be made to the SBC (which should give you an idea in the direction we are going) and then those changes will also come to the PBX.

 

[sdg]

Hi John

Thank you for your swift responses thus far.

We will look forward to the coming future changes towards the failover system!

Kind regards