Configuring Dhcp For Cisco Unified Srst Phones - Cisco CP-7911G-CH1 System Administrator Manual

How to Set Up the Network

Configuring DHCP for Cisco Unified SRST Phones

To perform this task, you must have your network configured with DHCP. For further details about
DHCP configuration, see the
Communications Manager documentation.
When a Cisco IP phone is connected to the Cisco Unified SRST system, it automatically queries for a
DHCP server. The DHCP server responds by assigning an IP address to the Cisco IP phone and
providing the IP address of the TFTP server through DHCP option 150. Then, the phone registers with
the Cisco Unified Communications Manager system server and attempts to get configuration and phone
firmware files from the Cisco Unified Communications Manager TFTP server address provided by the
DHCP server.
When setting up your network, configure your DHCP server local to your site. You may use your SRST
router to provide DHCP service (recommended). If your DHCP server is across the WAN and there is an
extended WAN outage, the DHCP lease times on your Cisco Unified IP Phones may expire. This may
cause your phones to lose their IP addresses, resulting in a loss of service. Rebooting your phones when
there is no DHCP server available after the DHCP lease has expired will not reactivate the phones,
because they will be unable to obtain an IP address or other configuration information. Having your
DHCP server local to your remote site ensures that the phones can continue to renew their IP address
leases in the event of an extended WAN failure.
Choose one of the following tasks to set up DHCP service for your Cisco UnifiedIP Phones:
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•
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Defining a Single DHCP IP Address Pool
This task creates a large shared pool of IP addresses in which all DHCP clients receive the same
information, including the option 150 TFTP server IP address. The benefit of selecting this method is
that you set up only one DHCP pool. However, defining a single DHCP IP address pool can be a problem
if non-IP phone clients need to use a different TFTP server address.
SUMMARY STEPS
1.
2.
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5.
Cisco Unified SCCP and SIP SRST System Administrator Guide
70
Cisco IOS DHCP Server
Defining a Single DHCP IP Address Pool, page
router is a DHCP server and if you can use a single shared address pool for all your DHCP clients.
Defining a Separate DHCP IP Address Pool for Each Cisco Unified IP Phone, page
method if the Cisco Unified SRST router is a DHCP server and you need separate pools for
non-IP-phone DHCP clients.
Defining the DHCP Relay Server, page
a DHCP server and you want to relay DHCP requests from IP phones to a DHCP server on a different
router.
ip dhcp pool pool-name
network ip-address [mask | prefix-length]
option 150 ip ip-address
default-router ip-address
exit
document and see your Cisco Unified
70:Use this method if the Cisco Unified SRST
72: Use this method if the Cisco Unified SRST router is not
Setting Up the Network
71: Use this
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