Remote Physical Phones - 3CX SBC Question

[amir_]

We have some elderly staff that MUST have physical phones at home. We are considering deploying 3CX SBCs on Raspberry PIs at these home users networks.

I'm interested to hear from others who have done this. Have you used the CanaKits or have you deployed your own Raspberry PIs?

https://www.3cx.com/community/threads/raspberry-pi-pre-installed-with-3cx-for-just-99.77438/

Regards,

Amir

 

[Evolute IT]

We have some elderly staff that MUST have physical phones at home. We are considering deploying 3CX SBCs on Raspberry PIs at these home users networks.

I'm interested to hear from others who have done this. Have you used the CanaKits or have you deployed your own Raspberry PIs?

https://www.3cx.com/community/threads/raspberry-pi-pre-installed-with-3cx-for-just-99.77438/

Regards,

Amir

Canakit is great for an SBC. It comes preloaded with Raspian so all you have to do is run the install script.

We installed one last week.

Make sure to set a static IP or a DHCP reservation for the SBC, and configure that IP in the 3CX Phone Provisioning tab.

 

[Alphabetic]

Depends on the network.

Are we talking 1 phone per home? You'd probably get away with STUN without having to forward anything.

 

[JohnS_3CX]

Hi Amir, it should be fairly easy. Learn the IP range of their ISP's modem, and set the SBC IP to static, taking the last available IP in their subnet to minimize the chance of any conflict. Even if the modem is ever replaced or reset by ISP technicians, your SBC should remain unaffected as no ports need to be forwarded.

From there, once the phone is plugged in you can remotely configure it to your PBX. The Pi can be plugged straight into the modem with a short LAN cable, and kept neatly right next to it (avoid on top, those modems tend to heat up quite a bit!).

The only issue you might face is in case the power is lost and the SD card gets corrupted.. but they tend to be very resilient overall and can usually recover automatically from power failures.

 

[amir_]

Canakit is great for an SBC. It comes preloaded with Raspian so all you have to do is run the install script.

We installed one last week.

Make sure to set a static IP or a DHCP reservation for the SBC, and configure that IP in the 3CX Phone Provisioning tab.

Hi Frederick,

Thanks for your responce. Where would the SBC sit in the end users home network?

Internet >>WAN Interface- Cable Modem - LAN Interface >>> SBC >>> Phone

Assuming that simple topology is accurate - wouldn't the LAN side of the cable modem be private address space? Then that would place the SBC on private address space as well.

I must be missing something here.

 

[Alphabetic]

Modem?

Where is the NAT Device? Do they not have a router?

 

[amir_]

Depends on the network.

Are we talking 1 phone per home? You'd probably get away with STUN without having to forward anything.

Hi,

Thanks for your response. Yes - these are individual home users with a single phone in their home network environment. The "network" is not managed by our company. Its the home users broadband connection and we just need to drop phones into it.

When you build out STUN - does it require the home user cable modem to have a static IP address ? None of our users have static addresses. Also, since we restrict our SBC to only allow inbound SIP traffic from our SIP Telephony Service provider address range - how would this home user phone traffic come into our network. Would we have to allow ANY ANY inbound rule for SIP traffic on our SBC?

 

[amir_]

Modem?

Where is the NAT Device? Do they not have a router?

This is a typical home user environment with a broadband cable modem and then users generally have some kind of router with integrated access point which does the NAT.

So my topology should be modified to reflect that router:

Internet >>>WAN - Cable Modem - LAN >>> ROUTER >>> SBC >>> Phone

 

[Alphabetic]

Hi,

Thanks for your response. Yes - these are individual home users with a single phone in their home network environment. The "network" is not managed by our company. Its the home users broadband connection and we just need to drop phones into it.

When you build out STUN - does it require the home user cable modem to have a static IP address ? None of our users have static addresses. Also, since we restrict our SBC to only allow inbound SIP traffic from our SIP Telephony Service provider address range - how would this home user phone traffic come into our network. Would we have to allow ANY ANY inbound rule for SIP traffic on our SBC?

Yes, if you're restricting 5060 to your SIP provider you'll be better off with an SBC at their home.

Find out their IP range, preconfigure the SBC with the static IP details and go plug it in to their router.

Providing that their firewall device is a router and not purely a modem.

 

[amir_]

Hi Amir, it should be fairly easy. Learn the IP range of their ISP's modem, and set the SBC IP to static, taking the last available IP in their subnet to minimize the chance of any conflict. Even if the modem is ever replaced or reset by ISP technicians, your SBC should remain unaffected as no ports need to be forwarded.

From there, once the phone is plugged in you can remotely configure it to your PBX. The Pi can be plugged straight into the modem with a short LAN cable, and kept neatly right next to it (avoid on top, those modems tend to heat up quite a bit!).

The only issue you might face is in case the power is lost and the SD card gets corrupted.. but they tend to be very resilient overall and can usually recover automatically from power failures.

So the topology would look like this and we hard code the SBC WAN port to the last address in the router's DHCP scope - which would be RFC 1918 address space:

Internet >>>Cable Modem>>> Router >>> SBC >>> Phone

 

[JohnS_3CX]

Pretty much yes, to clarify:

Internet >>>Cable Modem>>> Router >>> SBC i.e. 192.168.1.253 Static

Internet >>>Cable Modem>>> Router >>> Phone i.e. 192.168.1.xxx via DHCP

 

[amir_]

Pretty much yes, to clarify:

Internet >>>Cable Modem>>> Router >>> SBC i.e. 192.168.1.253 Static

Internet >>>Cable Modem>>> Router >>> Phone i.e. 192.168.1.xxx via DHCP

You wrote:
From there, once the phone is plugged in you can remotely configure it to your PBX.

Don't we have to "pre-provision" the SBC at our office and then ship it to the home user?

Regards,

Amir

 

[cobaltit]

Just to clarify. The phone doesn't sit behind the 3CX SBC per se, it just needs to be on reachable by the phone with no NAT between the two. The diagram 'looks' like you imagine connecting the phone to the SBC as if it had 2 ethernet ports.

You wouldn't want the SBC to be static inside the DHCP scope, even at the end. While Windows will fill a DHCP scope from the bottom up or low to high, may other DHCP servers will go top down or completely random so you would definitely want it outside the scope.

But weren't you working on OVPN earlier? Did that not pan out?

 

[amir_]

Just to clarify. The phone doesn't sit behind the 3CX SBC per se, it just needs to be on reachable by the phone with no NAT between the two. The diagram 'looks' like you imagine connecting the phone to the SBC as if it had 2 ethernet ports.

You wouldn't want the SBC to be static inside the DHCP scope, even at the end. While Windows will fill a DHCP scope from the bottom up or low to high, may other DHCP servers will go top down or completely random so you would definitely want it outside the scope.

But weren't you working on OVPN earlier? Did that not pan out?

lol - Yes we were. But we are experiencing one way audio! I've just sent an inquiry to your Cobalt IT info email asking for someone to call me to discuss engaging your company to assist us with this effort.