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Hosted SIP Phones with Outbound FXO Survivability Sample Configuration

Hosted SIP Phones with Outbound FXO Survivability Sample Configuration

Hosted SIP Phones with Outbound FXO Survivability Sample Configuration

This sample configuration below contains the commands needed for FXO survivability of hosted SIP phones running through the AOS SIP Proxy.  For the below sample configuration, the following is assumed about the application:

  • IP interfaces, routing, and firewall features have already been enabled.
  • There are no other voice trunks or voice grouped-trunks configured.
  • The SIP phones are configured for DHCP and will receive their IP address, default gateway, DNS server, and NTP server from the ADTRAN.  The appropriate DHCP options needed for the SIP phones to contact their configuration server will need to be added to the DHCP pool configuration.
  • The ADTRAN unit is equipped with a FXO port.  The ERL tool needs to be run on products that support it.  Details regarding usage of the ERL tool can be found on page 3 of the Analog Configuration and Trunk Troubleshooting Guide. Products that do not support the ERL tool may need to issue the command blind-dial under the analog voice trunk.

The following are key notes regarding the application:

  • The ADTRAN unit will be configured to act as a DNS proxy, which is required during survivability when a FQDN is used for the SIP server, outbound proxy, or registrar. The command voip name-service host <FQDN> sip udp ensures that the specified FQDN persists even when connectivity to the unit’s DNS server has been lost.  An entry will need to be made for every FQDN the SIP phones are configured to send SIP traffic to. If a phone fails to resolve a FQDN, the phone will not attempt to register or make/receive phone calls.
  • The ADTRAN can be configured to allow the registration of SIP phones during failover with the sip proxy failover accept-registrations command. This configuration command is desirable if the end users reboot their phones during survivability. When choosing whether or not to use this command, be aware that the command opens the unit up to accept ALL registrations during survivability.  This means that any rogue SIP device on the LAN can register to the unit during survivability and make calls to other SIP proxy users.
  • If you would like to route emergency calls out the FXO port(s), you can optionally add the command sip proxy emergency-call-routing accept 911.

Additional Resources:


domain-proxy failover

domain-lookup database local



ip dhcp pool "PHONES"





  timezone-offset -6:00


interface eth 0/2

  ip address

  ip access-policy PHONES

  media-gateway ip primary

  no shutdown


voice trunk T01 type analog supervision loop-start

  connect fxo 0/0


voice grouped-trunk FAILOVER

  trunk T01

  accept NXX-NXX-XXXX cost 0

  accept 1-NXX-NXX-XXXX cost 0

  accept 011-$ cost 0

  accept 411 cost 0

  accept 611 cost 0

  accept 911 cost 0


ip sip

ip sip proxy

ip sip proxy transparent

Version history
Last update:
‎02-27-2013 10:43 AM
Updated by: