When the 802.1X host mode is multi-domain, a voice VLAN must be configured for the IP phone. Cisco recommends MDA rather than CDP bypass for IP phones on dot1x-secured ports.
Checked 2026-10-02
You must configure the voice VLAN for the IP phone when the host mode is set to multi-domain.
- Vendor
- Cisco
- Product
- Cisco IOS
- Subsystem
- 802.1X
- Deployment
- on-premises
- Region
- not restricted
- Release range
- IOS 15M&T
- Checked
- 2026-10-02
Sources
- 802.1X Authentication Services Configuration Guide, Cisco IOS Release 15M&T - IEEE 802.1X Multidomain Authentication — Cisco Systems · tier 2 current vendor documentation · Guidelines for Configuring IEEE 802.1X Multidomain Authentication
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-mda-voice-vlan-required. WarmTransfer. https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-mda-voice-vlan-required
BibTeX
@misc{warmtransfer-claim-ip-phone-dhcp-vlan-troubleshooting-mda-voice-vlan-required,
title = {Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-mda-voice-vlan-required},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-mda-voice-vlan-required},
note = {Source note ip-phone-dhcp-vlan-troubleshooting-mda-voice-vlan-required, checked 2026-10-02}
}