100-890 · Question #54
From which network service does a Cisco IP phone request the configuration file during the bootup process?
The correct answer is E. TFTP server. See the full explanation below for the reasoning.
Question
From which network service does a Cisco IP phone request the configuration file during the bootup process?
Options
- ACisco Unified Communications Manager
- BDHCP server
- CCisco Catalyst switch
- DPhone's local default configuration in the flash memory is used
- ETFTP server
How the community answered
(28 responses)- A4% (1)
- C7% (2)
- D14% (4)
- E75% (21)
Community Discussion
6
Brenda K.Jun 26, 2026TFTP server, and this is a quick win you should nail in under 20 seconds. During bootup, the Cisco IP phone gets its IP info from DHCP (including the TFTP server address), then reaches out to that TFTP server to download its configuration file, which is why E is the answer and not A or B.
Luis F.Jun 26, 2026So I got this one wrong the first time and picked A because I figured the Unified Communications Manager would handle everything, but nope. The phone actually boots up and gets an IP from DHCP first, then the DHCP response points it to a TFTP server, and THAT is where it goes to grab the config file. Think of it like a PXE boot situation if you have ever set up a diskless workstation, same kind of idea where the device needs a lightweight protocol to pull down its config before it is fully running. Quick question though, does anyone know what specifically is in that config file the phone downloads, like is it just the CUCM address or does it include firmware info too?
Anjali D.Jun 27, 2026Good catch on the PXE parallel, and to answer your question the config file pulled via TFTP does include both the CallManager IP and the firmware load file name, so the phone can check if it needs to update before registering.
Bao N.Jun 26, 2026TFTP server is the right call here. After the phone grabs its IP and TFTP server address from DHCP, it reaches out to that TFTP server specifically to pull down its config file, which is the step that trips people up when they confuse the DHCP step with the config file step.
Anjali D.Jun 26, 2026The DHCP server tells the phone WHERE to go, but TFTP is what actually delivers the config file, so E.
Brenda K.Jun 29, 2026TFTP delivers the file for sure, but do not sleep on option 150 or 66 in the DHCP scope, since pointing the phone to the TFTP server IP is half the battle and a lot of people blank on that under pressure.