Using IP Phones with OnRelay

OnRelay is a mobile business phone system, which means all functionality is available from the OnRelay mobile app. So for most staff it is sufficient to use only smartphones.

OnRelay however also doubles as an advanced cloud VoIP service, and integration with physical desk phones is entirely seamless. With a Fixed Mobile User license it is possible to pair landline IP phones with your smartphone apps.

Please follow the below general guidelines to pair physical IP phones with OnRelay’s mobile app:

Rollout Strategy

As a rule of thumb we recommend a conservative approach to rolling out IP phones. We have found many businesses do not have the IT management capabilities to properly support a large number of IP phones on their network infrastructure, whereas managing just a few phones is unproblematic. So most of our customers use IP phones only for receptionists, office managers and very heavy phone users.

Office Network and Internet Connection

IP phones use your local area network and your public Internet connection to connect to OnRelay’s servers. So using IP phones with OnRelay requires a stable high capacity Internet connection from your Internet provider.

The VoIP traffic must traverse both your office firewall and your office router, which implies using Network Address Translation (NAT) between the public Internet and your local area network. NAT problems is a common culprit for VoIP problems, so please follow these guidelines to ensure VoIP traffic can seamlessly pass in both directions across your Internet router:

  • Leave your router settings with default settings (except SIP ALG, see below). Do not use any firewall port forwarding, demilitarized zones, separate virtual networks for VoIP, VoIP traffic priority or similar advanced router settings. It will most likely create more problems than they resolve, and be very difficult for OnRelay’s reps to troubleshoot remotely.
  • Use only one router between your IP phones and your Internet provider. Multiple routers mean multiple NAT hops, which is asking for trouble.
  • OnRelay use many advanced security tools to prevent hacker break ins. To circumvent some of these tools we whitelist your company’s public IP in our firewalls. So we recommend you get a static IP from your Internet provider to ensure your IP phones are not inadvertently blocked by OnRelay’s firewalls.
  • You may connect your Polycom IP phones using a WiFi USB dongle, but if so ensure you have excellent WiFi coverage where you place your IP phones.
  • OnRelay requires standard SIP TCP & UDP ports 5060-5061 and RTP UDP ports 30 000 – 32 000 to be open towards its servers. This traffic is normally allowed per default in standard routers.

Disable SIP ALG in Your Router!

You must ensure a function called ‘SIP ALG’ is disabled in all your Internet router / firewall.  Otherwise both inbound and outbound VoIP calls may be affected, and you will likely experience odd issues such as random call drops, incoming calls not alerting or failing to connect. The reason is that SIP ALG is poorly implemented in most commercial routers. It is a so called Application Level Gateway (ALG) for VoIP traffic intended to give VoIP priority, but instead SIP ALG unpredictably breaks VoIP call flows.

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. The routers that cannot disable SIP ALG must be replaced for IP Phones to work with OnRelay.  

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

Polycom IP Phones

OnRelay supports Polycom’s VVX series IP phones, 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 a Polycom VVX IP 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 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’.