After an 8800 phone reboots, the switch locks to CDP or LLDP for power negotiation, using whichever protocol the phone sends first with a power TLV. If that protocol is then disabled, the phone cannot power its accessories because the switch ignores power requests in the other protocol.
Checked 2026-10-02
The switch locks to the first protocol (containing a power Threshold Limit Value) that the phone transmits.
- Vendor
- Cisco
- Product
- Cisco IP Phone 8800 Series
- Subsystem
- PoE
- Deployment
- on-premises
- Region
- not restricted
- Release range
- current as of 2026-10-02
- Checked
- 2026-10-02
Sources
- Cisco IP Phone 8800 Series Administration Guide for Cisco Unified Communications Manager - Technical Details — Cisco Systems · tier 2 current vendor documentation · VLAN Interaction / Power Negotiation note
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-poe-protocol-lock. WarmTransfer. https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-poe-protocol-lock
BibTeX
@misc{warmtransfer-claim-ip-phone-dhcp-vlan-troubleshooting-poe-protocol-lock,
title = {Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-poe-protocol-lock},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-poe-protocol-lock},
note = {Source note ip-phone-dhcp-vlan-troubleshooting-poe-protocol-lock, checked 2026-10-02}
}