Using Cisco Ip Phones With A Dhcp Server - Cisco Catalyst 6500 Series Configuration Manual

Configuring the DHCP Server
(Optional) To specify the IP address(es) of the DNS server(s) the client will use, enter the following
Step 2
command:
FWSM/contexta(config)# dhcpd dns dns1 [ dns2 ]
You can specify up to two DNS servers.
(Optional) To specify the IP address(es) of the WINS server(s) the client will use, enter the following
Step 3
command:
FWSM/contexta(config)# dhcpd wins wins1 [ wins2 ]
You can specify up to two WINS servers.
(Optional) To change the lease length to be granted to the client, enter the following command:
Step 4
FWSM/contexta(config)# dhcpd lease lease_length
This lease equals the amount of time (in seconds) the client can use its allocated IP address before the
lease expires. Enter a value between 0 to 1,048,575. The default value is 3600 seconds.
Step 5 (Optional) To configure the domain name the client uses, enter the following command:
FWSM/contexta(config)# dhcpd domain domain_name
Step 6 To enable the DHCP daemon within the FWSM to listen for DHCP client requests on the enabled
interface, enter the following command:
FWSM/contexta(config)# dhcpd enable interface_name
For example, to assign the range 10.0.1.101 to 10.0.1.110 to hosts connected to the inside interface, enter
the following commands:
FWSM/contexta(config)# dhcpd address 10.0.1.101-10.0.1.110 inside
FWSM/contexta(config)# dhcpd dns 209.165.201.2 209.165.202.129
FWSM/contexta(config)# dhcpd wins 209.165.201.5
FWSM/contexta(config)# dhcpd lease 3000
FWSM/contexta(config)# dhcpd domain example.com
FWSM/contexta(config)# dhcpd enable inside

Using Cisco IP Phones with a DHCP Server

Enterprises with small branch offices that implement a Cisco IP Telephony Voice over IP (VoIP) solution
typically implement Cisco CallManager at a central office to control Cisco IP Phones at small branch
offices. This implementation allows centralized call processing, reduces the equipment required, and
eliminates the administration of additional Cisco CallManager and other servers at branch offices.
Cisco IP Phones download their configuration from a TFTP server. When a Cisco IP Phone starts, if it
does not have both the IP address and TFTP server IP address preconfigured, it sends a request with
option 150 or 66 to the DHCP server to obtain this information.
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Cisco IP Phones might also include DHCP option 3 in their requests, which lists the IP addresses of
default routers.
Cisco IP Phones might include both option 150 and 66 in a single request. In this case, the FWSM DHCP
server provides values for both options in the response if they are configured on the FWSM.
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide
8-20
DHCP option 150 provides the IP addresses of a list of TFTP servers
DHCP option 66 gives the IP address or the host name of a single TFTP server.
Chapter 8 Configuring IP Addresses, Routing, and DHCP
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