Hunt Group member limit on CUCM 6.1?

Unanswered Question
Sep 13th, 2010


I have an issue I need to confirm.  We have CUCM 6.1.

We have a Hunt Group configured using Broadcast for the algorithim.

We have 18 members in that group.  Before it was 16 members

Doing this only one phone is not able to ring in the hunt group and matching the configuration from the other phones.

Is there a limitation to the number of Hunt Group members on Cisco UCM 6.1 ?

Thank you!


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Justin Brenton Mon, 09/13/2010 - 20:44

These new members are not shared lines are they? And the line is not call forwarded to voicemail?

Jaime Valencia Tue, 09/14/2010 - 07:37

There are limits:

Hunt Pilot Scalability

Cisco recommends using the following guidelines when deploying call  coverage using top-down, circular, and longest-idle algorithms:

The Unified CM cluster supports a  maximum of 15,000 hunt list devices.

The hunt list devices may be a  combination of 1500 hunt lists with 10 IP phones in each hunt list, or a  combination of 750 hunt lists with 20 IP phones in each hunt list.  However, an increase in a number of hunt lists can require increasing  the dial plan initialization timer specified in the Unified CM service  parameters. Cisco recommends setting the dial plan initialization timer  to 600 seconds if 1500 hunt lists are configured.

Note When using the broadcast  algorithm for call coverage, the number of hunt list devices is limited  by the number of busy hour call attempts (BHCA). Note that a BHCA of 10  on a hunt pilot pointing to a hunt list or hunt group containing 10  phones and using the broadcast algorithm is equivalent to 10 phones with  a BHCA of 10.

Cisco recommends having a maximum of 35  directory numbers in a single line group configured to send the calls  simultaneously to all DNs. Additionally, the number of broadcast line  groups depends on the BHCC. If there are multiple broadcast line groups  in a Unified CM system, the number of maximum directory numbers in a  line group must be less than 35. The number of busy hour call attempts  (BHCA) for all the broadcast line groups should not exceed 35 calls set  up per second.



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ryabutler Tue, 09/14/2010 - 08:50


So where can the BHCA be configured, adjusted, or viewed?  Is this under the Line Group or some other location?

Thank you!


Jaime Valencia Tue, 09/14/2010 - 09:56

That's not something you configure or that CUCM can tell you.

From 8.X SRND

Busy Hour Call Attempts (BHCA)
The BHCA is the average number of calls per hour per device during the busy hour. (For example, the
busy hour for many systems is from 10:00 AM to 11:00 AM or from 2:00 PM to 3:0 PM.)
Unified CMBE supports a maximum of 3,600 BHCA. When calculating your system usage, stay within
the 3,600 BHCA maximum to avoid oversubscribing Unified CMBE.
The BHCA consideration becomes significant when the usage for any phone is above 4 BHCA. A true
BHCA value can be determined only by taking a baseline measurement of usage for the phone during
the busy hour. Extra care is needed when estimating this usage without a baseline.

Some examples for the calculation are given in the above link.



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brendand05 Tue, 09/14/2010 - 16:20

Hi Rya,

You are being led off track here.

There are no limits that should be affecting the sizes you mentioned in your post.

Our standard setup is that if the receptionist is unable to take an incoming call, the call queues for 1 minute, if it is still not answered it is broadcast to all of the office (except management) - The broadcast group is around 86 phones.

All phones are SCCP

Do a search on the DN that is not ringing, check that there are no shared lines or ghost DNs

Tapan Dutt Tue, 09/14/2010 - 18:08

look for the ghost DN's as well as the shared lines if any one of it is not the case then delete the DN from the line group and add it back in. Also reset the affected phone from the GUI


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