Most likely, the Cisco Analog Telephone Adaptor (ATA) 186 TftpURL parameter is not set with the correct URL or IP address of the TFTP server hosting the Cisco ATA 186 profile.
This resolution applies for cases where the Cisco ATA 186 receives the TFTP server address (IP address or URL) through a DHCP server.
To resolve this issue, perform these steps:
Ensure that the Cisco ATA 186 parameter TftpURL is set to 0.
If the DHCP server provides a URL to locate the TFTP server, ensure that the Cisco ATA 186 parameters DNS1IP and DNS2IP are properly set. For this to occur, the Cisco ATA needs a Domain Name System (DNS) server to resolve the URL.
If the DHCP server provides an IP address to locate the TFTP server, the Cisco ATA 186 does not need to consult with a DNS server.
If using DHCP server-assigned DNS server addresses to resolve DNS requests, ensure that the DNS1IP and DNS2IP parameters are set to 0.