DHCP configuration

Given a scenario of auto-assigning the range of address 192.168.30.0/24 to your host and to reserve the first 10 ip of the range to your static devices such as servers, printers, routers' interfaces etc ... ...


ip dhcp excluded-address 192.168.30.1 192.168.30.10  => tell dhcp server no to assign 1st 10 address


ip dhcp pool TEST  => create a TEST pool to start assigning address
network 192.168.30.0 255.255.255.0  
=> range of address to assign, will check with excluded-address to start the ip assignment
default-router 192.168.30.1  => define the default gateway to be used by PC
dns-server 192.168.30.10  => define the dns server to be used for resolving URL to IP address




For Voice configuration support
option 150 ip 192.168.30.1  => assuming CME installed on the router


Why option 150?
Cisco phones require access to a TFTP server that contains device configuration name files (.cnf file format), which enables the device to communicate with Cisco Call Manager. 

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 pre configured, it sends a request with option 150 to the DHCP server to obtain this information.


DHCP Option 150 is Cisco proprietary. The IEEE standard that matches with this requirement is Option 66. Like option 150, option 66 is used to specify the Name of the TFTP server.


Option 66 is an open standard juniper supports it. RFC 2132 defines option 66.

Difference between option 150 and option 66

• DHCP option 150 supports a list of TFTP servers (Multiple Server IPs)
• DHCP option 66 only supports the IP address or the hostname of a single TFTP server.