On Catalyst 9300 (IOS XE 17.15.x), CDP must be enabled on the port connected to a Cisco IP phone for the switch to send it the voice VLAN configuration, and CDP is globally enabled by default on all interfaces.

Checked 2026-09-24

You must enable CDP on the device port connected to the Cisco IP Phone to send the configuration to the phone. (CDP is globally enabled by default on all device interfaces.)
Vendor
Cisco
Product
Catalyst 9300 Series Switches
Subsystem
voice VLAN / CDP
Deployment
on-premises
Region
not restricted
Release range
IOS XE 17.15.x
Checked
2026-09-24

Sources

Cite this note

APA

WarmTransfer. (2026, September 24). Voice VLAN and LLDP-MED and CDP and PoE for IP phones: source note voice-vlan-lldp-poe-c9300-vv-cdp-required. WarmTransfer. https://warmtransfer.net/knowledge/claims/voice-vlan-lldp-poe-c9300-vv-cdp-required

BibTeX

@misc{warmtransfer-claim-voice-vlan-lldp-poe-c9300-vv-cdp-required,
  title  = {Voice VLAN and LLDP-MED and CDP and PoE for IP phones: source note voice-vlan-lldp-poe-c9300-vv-cdp-required},
  author = {{WarmTransfer}},
  year   = {2026},
  url    = {https://warmtransfer.net/knowledge/claims/voice-vlan-lldp-poe-c9300-vv-cdp-required},
  note   = {Source note voice-vlan-lldp-poe-c9300-vv-cdp-required, checked 2026-09-24}
}

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