what is the "Alternate TFTP" used for in Cisco IP Phone?

[Oak Ridge]

I know we can either manually setup the TFTP server, or setup it via DHCP option 150.

so  what is the "Alternate TFTP" used for in Cisco IP Phone if it is set to "YES", but still using DHCP option 150?

[Brandon Pierce]

As I recall the alternate will override the DHCP set one.

[Chris Deren]

Brandon is correct (+5) from Cisco guide:

You can configure phones with the IP address of the TFTP server. If DHCP is enabled on the phone, you can still configure an alternate TFTP server IP address locally on the phone that will override the TFTP address that was obtained through DHCP.

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/7_1_2/ccmsys/accm-712-cm/a02tftp.html

[AK007]

So , Objective of this option was to Override the Existing TFTP settings in the phone manually. ( Ideally phones will have TFTP Server 1 , TFTP Server 2 field populated using info got from DHCP Option 150 )

In case of Cisco IP Phones , You might sometimes be required to point it to an entirely different TFTP Server for testing purpose . If the requirement is for just only one phone, then we don't have to change it globally on the DHCP scope. Instead just locally on the phone itself would be a better option. 

In such scenarios , then you can make use of this Alternate TFTP Option.

Note : Its only Manually configurable through direct physical access into the phone.

Reference : https://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cuipph/8800-series/english/adminguide/P881_BK_C136782F_00_cisco-ip-phone-8800_series/P881_BK_C136782F_00_cisco-ip-phone-8811-8841_chapter_01110.html 

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