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Hunt Groups in Business Continuity

A Hunt Group is a set of extension numbers that are grouped as a single logical unit. Depending on the Hunt Group call distribution strategy (sequential or parallel), an incoming call is propagated to one or all extensions within the group. Hunt Groups with the parallel distribution strategy (simultaneous ringing) are now supported in Business Continuity deployments.

Hunt Group Preferred Site

In DR mode (when both DR peers are running and connected to each other), one DR peer is considered a preferred site for a Hunt Group. The preferred site is configured by the hg-preferred-site option of the corresponding Hunt Group DN. When an inbound call arrives at a Hunt Group, SIP Server checks if the current site is the Hunt Group preferred site. If it is, the call is processed as usual and distributed to Hunt Group members. If it is not, the call is redirected to the preferred site using the DR call forwarding procedure. So, the outgoing calls to Hunt Group members are always distributed from the Hunt Group preferred site. The DR call forwarding procedure is not used for calls distributed from the Hunt Group. Instead, outgoing calls are distributed only to Hunt Group members on a local DN, regardless of the agent presence on this DN.

If a DR peer fails, the remaining DR peer switches to the standalone HA mode and distributes all inbound Hunt Group calls to Hunt Group members; no preferred site check is performed. The same happens if a connection between DR peers is lost—each site tries to distribute all inbound Hunt Group calls locally. This distribution can be successful if on the site where an inbound call arrives, at least one DN belonging to a Hunt Group member is in service. Otherwise, the default routing destination applies.

Agent Desktop Considerations

To have a call visible on an agent desktop, the desktop must be connected to the Hunt Group preferred site. The agent desktop preferred site must be set to the same value as the Hunt Group preferred site. If the agent desktop connects to the non-preferred site and tries to log in an agent, SIP Server allows this login but notifies the agent desktop through a special EventPrivateInfo containing the name of the SIP Server DR peer.

In case of preferred site failure and recovery from the failure, SIP Server notifies agent desktops about Hunt Group members through EventPrivateInfo recommending them to log in to the Hunt Group preferred site.

SIP Phone Connections

In Business Continuity deployments, SIP phones must be connected to both DR peers simultaneously, where dual registration is strongly recommended. For single-registration SIP phones, some limitations apply. Based on its configuration, the phone chooses the preferred site to send outgoing calls and handle outgoing SIP traffic.

Feature Configuration

On a DN of type ACD Queue, specify the following configuration option in the [TServer] section:

  • hg-preferred-site

For Business Continuity deployments, see Basic Deployment for details.


Default Value: No default value
Valid Values: Any string value
Changes Take Effect: For next call distribution

Specifies the name of the SIP Server DR Peer application corresponding to the preferred Hunt Group site. If not set or set to an invalid application name, the preferred Hunt Group site cannot be determined, and inbound Hunt Group calls are processed at the site where they are received.

Feature Limitations

  • If a preferred site fails, calls can be delivered to an agent phone when an agent desktop is not yet logged in to the non-preferred site.
  • If a connection between DR peers is lost, Hunt Group members might receive calls even if they are already on calls at the other peer.
  • If an agent desktop does not comply with the recommendation to reconnect to the preferred Hunt Group site, or a connection to the DR peer is unavailable for the desktop and SIP phone is still connected to both sites, there is a risk of non-monitored calls arriving at the agent phone. This situation can also occur if different preferred sites are configured for the desktop and for the Hunt Group.
  • During preferred site startup, inbound Hunt Group calls are routed to a default destination on the preferred site until agents/phones become available at this site.
  • For single registration SIP phones, the following limitations apply:
    • If inter-site connection is lost, only the preferred site distributes Hunt Group calls to the phones.
    • An alternate site will not distribute Hunt Group calls to phones until they REGISTER with the alternate site.

See other limitations common for Hunt Groups.

This page was last edited on September 29, 2015, at 21:32.
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