Cisco documents that enabling IEEE 802.1X on a Catalyst 9300 access port that has a voice VLAN and a connected Cisco IP phone causes the phone to lose connectivity to the switch for up to 30 seconds.
Checked 2026-10-02
If you enable IEEE 802.1x on an access port on which a voice VLAN is configured and to which a Cisco IP Phone is connected, the phone loses connectivity to the device for up to 30 seconds.
- Vendor
- Cisco
- Product
- Cisco Catalyst 9300 Series Switches
- Subsystem
- 802.1X
- Deployment
- on-premises
- Region
- not restricted
- Release range
- IOS XE 17.18.x
- Checked
- 2026-10-02
Sources
- VLAN Configuration Guide, Cisco IOS XE 17.18.x (Catalyst 9300 Switches) - Configuring Voice VLANs — Cisco Systems · tier 2 current vendor documentation · Voice VLAN configuration guidelines
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-vvlan-dot1x-30s-loss. WarmTransfer. https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-vvlan-dot1x-30s-loss
BibTeX
@misc{warmtransfer-claim-ip-phone-dhcp-vlan-troubleshooting-vvlan-dot1x-30s-loss,
title = {Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-vvlan-dot1x-30s-loss},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-vvlan-dot1x-30s-loss},
note = {Source note ip-phone-dhcp-vlan-troubleshooting-vvlan-dot1x-30s-loss, checked 2026-10-02}
}