Which DHCP Option to Configure for IP Telephony in Cisco Exam CLCOR?
Question
An engineer is configuring IP telephony.
The network relies on DHCP to provide TFTP server addresses to the endpoints.
Policy requires the endpoints to receive two server addresses.
Which DHCP option must be configured?
Answers
Explanations
Click on the arrows to vote for the correct answer
A. B. C. D.C.
The correct answer is option A: DHCP option 66 must be configured.
When an IP phone boots up, it uses DHCP to obtain an IP address, subnet mask, default gateway, DNS server, and TFTP server address. The TFTP server is used to download the phone's firmware and configuration files.
By default, Cisco IP phones only accept a single TFTP server address from the DHCP server. However, some organizations may require the phone to receive two TFTP server addresses for redundancy purposes.
To provide multiple TFTP server addresses to Cisco IP phones via DHCP, the DHCP server must be configured to send option 66. Option 66 is a DHCP option that specifies the TFTP server's hostname or IP address.
When option 66 is configured, the DHCP server sends a list of TFTP server addresses to the IP phone. The IP phone then attempts to download its firmware and configuration files from the first TFTP server in the list. If that server is unavailable, the phone tries the next server in the list.
Option 143 is not a valid DHCP option. Option 150 specifies the TFTP server's IP address, but it only allows for a single address. Option 166 is used for provisioning Cisco IP phones with XML configuration files and is not related to TFTP server addresses.
