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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.  

SIP ALG may have different names from different router suppliers. Some examples are 'SIP Transformations' and 'VoIP Application'.

OnRelay requires TCP & UDP ports 5060 and UDP ports 30 000 - 32 000 to be open towards its servers.

For most standard routers no changes are necessary to connect to OnRelay.

Typical symptoms for router configuration problems are:

  • The IP phone does not register, but displays 'URL Call Disabled' or similar technobabble. Check port 5060.
  • The IP phone registers, but does not connect calls. Check TCP / UDP ports 30 000 - 32 000 are open.
  • The IP phone is able to place and receive calls, but behaves in a funny way during the call, such as giving one-way media, not answering properly. Check SIP ALG.

Polycom IP Phones

OnRelay limits support of IP desk-phones for use with our Landline Pairing feature to Polycom's VVX and IP Soundstation series, as these devices are well standardised, robust and easily auto-provisioned. Note OnRelay's fixed mobile integration call flows are more advanced than regular VoIP calls, so verifying a large array of IP desk-phones with the service is not practical. 

To deploy an IP desk-phone with OnRelay please follow the below steps:

  • Ensure you have a Fixed Mobile User license for each user to whom you wish to assign an IP desk-phone.
  • Email the phone's MAC address to, and include which of your users / numbers or call group(s) you want to add to the phone. 
  • You will receive instructions to register the phone with OnRelay's provisioning server when the phone is ready. Only a few config changes are required. After the phone has been connected to OnRelay's provisioning server, all subsequent configuration changes are automated.
  • When you have correctly connected to OnRelay's provisioning server, the phone will take a few minutes to update its firmware to the latest version supported by OnRelay and receive its configuration files.

  • When the phone is ready to be used, it will show your name or line number on its display. 
  • You can test you are connected by dialing a company 3 digit extension or voice mail at 456. 
  • To dial an external line, you have to dial 9 and country code, e.g. 9 1 xxx xxx xxxx for the USA, 9 44 xxx xxx xxxx for the UK.
  • To receive calls, make sure you have enabled 'Landline Pairing' in your mobile app settings, and set Office Calls to 'Ring Both' or 'Ring Landline'.

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