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8x8 Support

8x8 Work SIP Error Codes Overview


Familiarizing yourself with common network troubleshooting tips can help resolve common error codes.

If any of these errors persist please reach out to your administrator or our support team for more troubleshooting help.

Understanding SIP

SIP (Session Initiation Protocol) is a signaling protocol widely used for setting up, connecting, and disconnecting communication sessions, typically voice or video calls over the Internet.   

SIP is an application-layer control protocol that supports five parts making and stopping communications. The five parts of setting up and terminating calls that SIP handles are:

  • User Location - Determines where the end system is for a call.
  • User Availability - Determination of the willingness (availability) of the called party to engage in a call.
  • User Capabilities - Determination of the media and parameters used for the call.
  • Session Setup - Establishment of the session parameters from both parties (ringing).
  • Session Management - Invoking the services, including transfer, termination, and modifying the session parameters.

Error Types

When seeing a message saying “Unable to connect to phone service” one of the following errors might be the main cause.

DNS Error

The VOClient stack was unable to resolve the IP address of the SIP server.

Potential causes

  • Customer DNS unreachable/misconfigured
  • 8x8 GTM DNS service unreachable/blocked

Potential solutions 

  • Check customer DNS configuration
  • Unblock access to 8x8 GTM DNS server
  • Network Error

Potential causes

  • Local connectivity issue
  • Remote SIP server port blocked by firewall
  • TCP protocol blocked by firewall
  • No route to a SIP server (routing issue)
  • TCP connection failure
  • TLS handshake failure (certificate error)

Potential solutions 

  • Check local connectivity (WiFi or Ethernet) 
  • Do you connect to other non-8x8 related services?
  • Check all firewall/router configurations
  • Check 8x8 SIP service ports are open
  • Ensure SIP traffic is not proxied (man-in-middle)
  • Ensure SIP ALG is disabled on the router

Failed Authentication 

The SIP authentication failed.

Potential causes

  • SIP username not found/provisioned
  • SIP password incorrect

Potential solutions 

  • Check the customer's account on the PBX.
  • Most often, resetting the customer's account resolves this issue.

Time Out Error

While trying to connect to the SIP server, there was some network-related error.

Potential causes

  • Very poor network connection
  • Firewall issue

Potential solutions 

  • Check local connectivity
  • Check firewall/router configuration

Other Error

More investigation is necessary to identify the potential causes.

Potential causes

  • Possible SIP ALG manipulating SIP packets
  • Some other internal SIP stack errors (rare)

Potential solutions 

  • Ensure SIP ALG is disabled on the router
  • Try forcing SIP connectivity over TLS

Known Limitations

Important-Icon.png As part of setting up telephony on a Windows system, 8x8 Work loads wlanapi.dll. Some antiviruses might flag this, as a result we do recommend adding an exception for 8x8 Work.

If you are unable to make or receive communications after reconfiguring your router, checking all cables, reconnecting phones, and establishing ports for each device, contact your ISP provider.

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