Compatibility Guide

Recommended Phones and Routers can be found in our Purchasing Guide.


Compatible Phones

While the OnSIP service supports a broad range of SIP features and functionality, any device which supports and is compliant with the following minimum requirements will work:

SIP RFC Support

  • RFC 2833 - RTP Payload for DTMF Digits, Telephony Tones and Telephony Signals
  • RFC 3261 - SIP: Session Initiation Protocol
  • RFC 3263 - Session Initiation Protocol (SIP): Locating SIP Servers
  • RFC 3264 - An Offer/Answer Model with the Session Description Protocol
  • RFC 3515 - The Session Initiation Protocol (SIP) Refer Method
  • RFC 4961 - Symmetric RTP / RTP Control Protocol (RTCP)

Please see Phone Configuration for phone configuration options.


Compatible Routers and Firewalls

Generally, we have found that OnSIP works great with all sorts of routers and firewalls so long as:

  • Any SIP ALG has been disabled (this is a function on some routers)
  • Any SIP firewall has been deactivated (this is a function on some routers)
  • Phones are located behind a single NAT server on your internal network

Note: No ports are required to be opened in order for the OnSIP Hosted PBX to work. The phones inside the network make the initial communication out to OnSIP and therefore open the port. All packets coming from OnSIP are in response to packets that originated on your network.

While the list of routers and firewalls known to work is far too long for us to practically maintain, routers from Cisco, Juniper, Linksys, D-Link, Apple and Edgebox among many others are known to work well.


Incompatible Hardware and Software

Incompatible hardware and software is that which tries to change the packet information but does so incorrectly. Many router manufacturers for instance have implemented what are known as SIP ALGs, application level gateways, that attempt to rewrite the SIP packets in order to traverse NATs. Unfortunately these companies are not experts in SIP and implement these gateways incorrectly.

Digium Phones

  • There is no identifiable field for outbound proxy, which means outbound calling to the PSTN does not work.
  • Dialing a non-existent extension renders the phone non-functional and a reboot is required.
  • Not recommended in the current state.

D-Link Routers (3.x firmware)

  • Includes a SIP Application Level Gateway (ALG) which always substitutes the external IP address for any internal IP address in SIP requests. Disabling the ALG drops all SIP packets.

Sonus Networks

  • Some versions of Sonus applications on some Sonus products have RFC 2833 DTMF interoperability issues with our service.

Unidata Phones

Yate Client

  • Supplants Auth ID with User ID. No separate field for Auth ID which means that a limited number of users can use this device with the OnSIP service.

Asus RT-N12

  • The Router would not allow SIP packets to pass through to our SIP Proxies in any form.

Cisco DPC39xxB

  • The router will not keep ports open and will re-assign recently used ports to other devices.


Updated October 2020

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