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OnRelay's Mobile Office Phone service doubles as a hosted VoIP service. With a Fixed Mobile User license it is possible to pair landline VoIP extensions with your mobile Office Phone app. You can also connect switchboard and conference room extensions via your local area network and internet connection. 

OnRelay however takes a very conservative approach when supporting customer VoIP landline extensions. We have found that many businesses do not have the IT management capabilities to properly support VoIP on their LANs / WANs. And it is necessarily their responsibility to ensure office or home network and internet connection have sufficient capacity, quality of service and connectivity to work properly with a hosted VoIP service.  

So we strongly suggest our customers think 'mobile first' since the Office Phone app is both more feature rich than a landline VoIP extension and also a lot simpler to deploy and manage:

(1) It uses public cellular networks, which are open such that voice traffic is not restricted by any routers or firewalls

(2) The cellular networks have known voice quality and no practical scalability or capacity limitations

(3) Smartphones are simpler, more uniform and better controlled app environments than PCs.

(4) The Apple and Google mobile app stores provide an automated app installation and upgrade platform 

(4) The Office Phone app is auto-provisioned and auto configured. No manual configuration data or credentials have to be entered.

So we strongly recommend you keep VoIP extensions to a minimum and encourage your staff to use their mobile Office Phone apps as much as possible. The key exception is of course if you have very poor cellular coverage in your building or area. To pair landline broadband SIP extensions with your OnRelay Office Phone mobile apps, please follow the below general guidelines.

Firewalls, NAT and SIP ALG

Network Address Translation (NAT) is supported with OnRelay's service, but you must ensure 'SIP ALG' is disabled in all your local network routers and firewalls for this to work.  Otherwise the SIP extension may still register with the OnRelay service, but both inbound and outbound calls will be affected, and you will experience issues such as call drops, incoming calls not alerting or failing to establish due to SIP signals being modified or blocked by the SIP ALG feature. 

Most home and office routers will not have SIP ALG enabled. But some routers are shipped with SIP ALG switched on per default.  Some of these again will have an option to disable SIP ALG, others do not. The routers that cannot disable SIP ALG must be replaced for SIP extensions to work with OnRelay.  

  • The following routers comes with SIP ALG enabled per default, but with an option to disable SIP ALG: 
    • Comcast SMC D3G: To resolve switch 'Smart Packet Detection' to off via admin interface
    • Netgear WNDR3400: Select 'Disable SIP ALG' from WAN Setup menu
    • Motorola NVG510: SIP ALG can be disabled via CLI command: set ip alg sip-enable off, telnet must be enabled first
  • The following routers must be replaced, as they have SIP ALG permanently switched on with no option to disable:
    • Comcast Xfinity (Technicolor) TC8305C
    • Comcast Business Netgear CG3000DCK

Please also ensure your Firewall allows traffic to TCP ports 5060/5061 and UDP ports 30,000-32,000 to / from our server.

Some networks are setup to route all Internet traffic via VPNs. This is not recommended for VoIP.  It is in some cases possible to bypass VPN DNS services by configuring the static IP of our server instead of its domain address when configuring PC softphones and IP phones..

Polycom IP Phones

OnRelay recommends Polycom's SIP desk-phones for use with our service, as they are well standardised, robust and easily auto-provisioned.  To deploy please follow the below steps:


  • Email the phone's serial number to, and include which of your users / numbers or call group(s) you want to add to the phone. 
  • You will receive a response from OnRelay when the phone is ready to be provisioned, including the server address, user ID and password required to register with the provisioning server.

  • Register your Polycom IP phone with the OnRelay auto-provisioning server as follows:

    • Reboot the phone

    • Press 'Setup' or 'Cancel' and then 'Setup' when the countdown is being displayed

    • Use the standard Polycom admin password of '456'

    • Scroll down to 'DHCP Menu' and press select/enter

    • Change the 'Boot Server' to 'Static' via the 'Edit' button

    • Press 'Back'

    • Scroll down to 'Server Menu' and press 'Select' / 'Enter' and change to the following values:

      • Server Type: FTP

      • Server Address: <received from OnRelay>

      • Server User ID: <received from OnRelay>

      • Server Password: <received from OnRelay>

  • Caveat: With Polycom, dialled digits can not be easily manipulated via the phone dial plan, so you must dial '9' before external numbers

Plantronics Headsets

Mobile users commonly use wireless Bluetooth headsets, and these are almost a must if you want to pair a PC or Mac Softphone with your mobile Office Phone app. All known commercial PC headsets work with OnRelay's service. 

OnRelay nevertheless recommends Plantronics Voyager Legend UC for the following reasons:

  • The Plantronics Voyager Legend UC can connect to both your smartphone and your PC at the same time.  This means that in combination with the OnRelay Ring Both feature you can always chose whether to answer the call on your smartphone or PC, which is really convenient if you e.g. plan to leave your desk during the call.
  • The Plantronics Voyager Legend UC headset reads the caller ID in your ear, and in combination with the OnRelay caller ID mechanism for Office Calls you can filter your office calls also in situations when it is difficult to see your smartphone screen, such as when driving.
  • OnRelay and Plantronics have in partnership developed some 'headset' awareness features, wherein e.g. it is possible to automatically set your 'Ready State' for receiving Group Calls based on whether your headset is switched on and connected with your mobile and PC.
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