With critical voice VLAN on Catalyst 9300 (IOS XE 17.15.x), a port goes into critical authentication mode when ISE does not respond, and a phone sending traffic tagged with the voice VLAN is placed in the configured voice VLAN.
Checked 2026-10-02
- Vendor
- Cisco
- Product
- Cisco Catalyst 9300 Series Switches
- Subsystem
- 802.1X
- Deployment
- on-premises
- Region
- not restricted
- Release range
- IOS XE 17.15.x
- Checked
- 2026-10-02
Sources
- Security Configuration Guide, Cisco IOS XE 17.15.x (Catalyst 9300 Switches) - Configuring IEEE 802.1x Port-Based Authentication — Cisco Systems · tier 2 current vendor documentation · Critical Voice VLAN
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-critical-voice-vlan. WarmTransfer. https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-critical-voice-vlan
BibTeX
@misc{warmtransfer-claim-ip-phone-dhcp-vlan-troubleshooting-critical-voice-vlan,
title = {Troubleshooting IP phones that do not get a voice VLAN or DHCP options: source note ip-phone-dhcp-vlan-troubleshooting-critical-voice-vlan},
author = {{WarmTransfer}},
year = {2026},
url = {https://warmtransfer.net/knowledge/claims/ip-phone-dhcp-vlan-troubleshooting-critical-voice-vlan},
note = {Source note ip-phone-dhcp-vlan-troubleshooting-critical-voice-vlan, checked 2026-10-02}
}