You want to add 90 IP phones to a UCM network.
You enable autoregistration in UCM and configure the Starting Directory Number field to 5000.
You also configure the Ending Directory Number field.
You connect the IP phones to the network. The secondtolast IP phone that you connect displays a dn of 5088.
However, the last IP phone that you connect never registers with UCM.
Which of the following is most likely the problem? (Select the best answer.)
A.
A rogue IP phone exhausted the dn pool.
B.
You configured the same dn for both the start and the end of the dn pool.
C.
You did not configure the last IP phone’s MAC address in UCM.
D.
You did not clear the Autoregistration Disabled on this Cisco Unified Communications Manager check box
in UCM.
Explanation:
Of the choices provided, the problem is most likely that a rogue IP phone has exhausted the directory number
(dn) pool. Autoregistration enables Cisco Unified Communications Manager (UCM) to automatically add new IP
phones to the UCM database as the IP phones are connected to the network. When a new IP phone is
connected to the network, UCM will automatically assign an unused dn to the IP phone from a specified pool of
dn numbers. The dn pool is assigned in order from the lowest available dn through the highest dn. Once the
pool of dn numbers is exhausted, new IP phones will not be able to autoregister with UCM.
Autoregistration is a security risk because rogue devices can be connected to the network and registered with
UCM by using autoregistration. In addition, you could accidentally register a valid IP phone with a dn from the
wrong dn pool if you leave autoregistration enabled after you have completed an autoregistration process.
Therefore, Cisco recommends that you enable autoregistration only for short periods of time, such as when you
need to add fewer than 100 IP phones to the network. In this scenario, you have configured autoregistration so
that UCM can allocate dns to 90 new IP phones. Because the last IP phone you connect cannot autoregister, it
is likely that a rogue IP phone autoregistered during the period of time that you enabled autoregistration to add
new IP phones. You could have also encountered this problem if the range of dns you configured was not large
enough to accommodate the 90 IP phones that you needed to add to UCM.
A missing IP phone Media Access Control (MAC) address in UCM cannot cause an IP phone to fail to autoregister. By design, the UCM autoregistration process does not require an administrator to configure IP phone
MAC addresses in UCM. However, if you manually provisioned IP phones or if you added new IP phones by
using the Bulk Administration Tool (BAT), you would need to configure MAC addresses for the IP phones in
UCM. When you are manually provisioning an IP phone in UCM, you must fill in the MAC Address field, the
Device Pool field, the Phone Button Template field, and the Device Security Profilefield.It is not likely that you configured the same dn for both the start and the end of the dn pool. When you enable
autoregistration in UCM, you must configure the Starting Directory Number field with a value that is lower than
the value of the Ending Directory Number field. If you do not properly configure the range of dns, UCM
automatically disables autoregistration. In this scenario, 89 legitimate new IP phones have already
autoregistered with UCM before the last IP phone fails. Therefore, it is not possible that autoregistration was
disabled because of an invalid dn range.
It is likely that the Autoregistration Disabled on this Cisco Unified Communications Manager check box is still
selected in UCM. If you provide a valid range of dns in the Starting Directory Number field and the Ending
Directory Number field, UCM will automatically clear the Autoregistration Disabled on this Cisco Unified
Communications Managercheck box, thus enabling autoregistration. In addition, in this scenario, 89 legitimate
new IP phones have already autoregistered with UCM before the last IP phone fails. Therefore, it is not likely
that the Autoregistration Disabled on this Cisco Unified Communications Manager check box is still selected in
UCM.https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/8_0_2/ccmsys/accm-802-cm/
a02autor.html#wp1020237