For IPv6 phones, the Cisco Unified CM 15 guide says to pass the TFTP server IPv6 address in Cisco vendor-specific DHCPv6 information (sub-option type 1), not in option 150, which is IPv4 only.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Cisco Unified Communications Manager
- Subsystem
- TFTP discovery
- Deployment
- on-premises
- Region
- not restricted
- Release range
- Release 15 and SUs
- Checked
- 2026-10-02
Sources
- System Configuration Guide for Cisco Unified Communications Manager, Release 15 and SUs - Configure TFTP Servers — Cisco Systems · tier 2 current vendor documentation · Configure TFTP Servers > Proxy TFTP deployment / DHCP options
Cite this note
APA
WarmTransfer. (2026, October 2). Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp. WarmTransfer. https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp
BibTeX
@misc{warmtransfer-claim-ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp,
title = {Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp},
note = {Source note ip-phone-dhcp-vlan-troubleshooting-cucm15-dhcpv6-tftp, checked 2026-10-02}
}