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documentation on voIpProt.OBP.dhcpv4.option and voIpProt.OBP.dhcpv4.type

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documentation on voIpProt.OBP.dhcpv4.option and voIpProt.OBP.dhcpv4.type

While reading through the release notes on the 5.5.x versions of UC, I stumbled across these new parameters getting introduced in 5.5.1. There is no Admin guide available for 5.5.0 and the admin guides for 5.6.0 and 5.7.0 still do not discuss these entries. What little information given seems to indicate that if I create a DHCP option 120 and set that field to lets say  it would use that ip as my outbound proxy. And should I need to set it to I would need to set voIpProt.OBP.dhcpv4.type="1" in a configuration file.  What is not explained is the following:


when creating option 120 in the isc dhcpd.conf what to define its type as. Should I assume that if 

voIpProt.OBP.dhcpv4.type is set to 0 I would use


option sip-outbound-proxy code 120 = ip-address;
option sip-outbound-proxy;

and if voIpProt.OBP.dhcpv4.type is set to 1 I would use

option sip-outbound-proxy code 120 = string;
option sip-outbound-proxy "";


It also does not indicate what effect this will have if the phone config already has reg.x.outboundProxy.address defined as some other value. Does dhcp override the config? or does the config override dhcp? Same question for voIpProt.SIP.outboundProxy.address


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Polycom Employee & Community Manager

Re: documentation on voIpProt.OBP.dhcpv4.option and voIpProt.OBP.dhcpv4.type

Hello @EEMAN,

welcome to the Polycom Community.

This seems to be missing from the Admin Guide and I raise this internally.


  • Verified that if nothing is configured for sip server and Vlan discovery mode is set to Fixed with vlan id option 128, option 128 is used to receive Vlan information and phone is moving to received vlan interface

  • Verified that if voIpProt.OBP.dhcpv4.option is not configured, option 120 is not requested

  • Verified that if voIpProt.OBP.dhcpv4.option="120" is configured, phone requests for DHCP option 120 and applies the outbound proxy obtained in DHCP to voIpProt.SIP.outboundProxy.address

  • Verified that if voIpProt.server.dhcp.option="128" is configured, phone requests for DHCP option 128 and applies the sip server obtained in DHCP to voIpProt.server.1.address

  • voIpProt.OBP.dhcpv4.type - This will define the type of OutBound Proxy address. If set to 0, type is IP address and if set to 1, type is string. Default value is 0


  • Verified that if voIpProt.OBP.dhcpv6.option="21" is configured, voIpProt.SIP.outboundProxy.address is configured with the domain name obtained from DHCPv6 option 21

  • Verified that if voIpProt.OBP.dhcpv6.option="22" is configured, voIpProt.SIP.outboundProxy.address is configured with the IP address obtained from DHCPv6 option 22
    voIpProt.server.1.address will be empty as nothing is obtained in V6

It overwrites the voIpProt.SIP.outboundProxy.address parameter. So the reg.* parameters would over ride it, but it would be used for any registration that didn’t over ride it in the reg.* parameters.

Please ensure to provide some feedback if this reply has helped you so other users can profit from your experience.

Best Regards

Steffen Baier

Polycom Global Services

The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. My official "day" Job is 3rd Level support at Poly but I am unable to provide official support via the community.


Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels.
Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's
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