The Auto-sense voice feature is an addition to the Auto-sense module. Based on the events of the phone discovery in the network, you can use this feature to configure phone devices without manual intervention.
After the switch discovers a Link Layer Discovery Protocol (LLDP) packet with phone capabilities, the port transitions to the "voice" state. The port receives a message on the voice event details.
With the Auto-sense voice feature, you can configure the voice I-SID and the voice VLAN. If you configure the I-SID as untagged, the phone receives VLAN as zero. When you configure Auto-sense voice, switched UNI is configured in VOICE I-SID for each port that is in "voice" state. The switch adds the Link Layer Discovery Protocol-Media Endpoint Discovery (LLDP-MED) policies for voice and voice-signaling Type-Length-Value (TLVs) to the LLDP packet and sends LLDP packets to the phone. It uses the configured voice VLAN and default values for Differentiated Services Code Point (DSCP) (46) and priority (6). After you run the auto-sense voice command, a filter is installed to prioritize the traffic that passes through the configured I-SID. The filter applies to traffic that reaches the VOICE I-SID, which implies the voice traffic.
Note
To change the Auto-sense voice configuration on the switch, delete the earlier configured voice I-SID and VLAN entry.
After you configure auto-sense voice, following tasks take place:
The I-SID <I-SID value> and C-VID <C-VID value> are saved in the control plane.
The voice I-SID is created.
The ports that are in the "voice" state process the voice configuration message and begin the dynamic configuration. This configuration includes the following tasks:
Creation of voice Switched UNI (S-UNI).
Deletion of onboarding and data I-SID, or S-UNI, if you configured auto-sense as "untagged".
Addition of LLDP-MED voice and voice-signaling TLVs to the LLDP packet and sending of LLDP packets to the phone.
The voice filter is updated. After you run the auto-sense voice command, a filter is installed to prioritize the traffic that passes through the configured I-SID. The filter applies to the traffic in Voice I-SID. The traffic that passes through this I-SID is internally prioritized with level 6 and forwarded with a dot1p value of 6, for tagged packets. For the IP packets, the DSCP value of 46 is forwarded.
Note
To disable Auto-sense on the port but keep the dynamic configurations made by Auto-sense, use the command no auto-sense enable convert-to-config. The voice S-UNI loses its Auto-sense origin and has a config origin instead. The LLDP-MED policies installed by Auto-sense are preserved.
If you use the no auto-sense voice command, the system removes the voice S-UNI and the LLDP-MED policies. The voice I-SID is removed if it was installed by using the auto-sense voice command. If the I-SID existed before you used the auto-sense voice command, the system does not remove the I-SID but the I-SID does lose its Auto-sense origin.
A port exits the voice state in one of the following scenarios:
If the port is down
If the LLDP session fails between the switch and the phone
If Auto-sense is disabled on the port that connects to the IP phone
After a port exits the voice state, the Switched UNI (S-UNI), LLDP voice and voice-signaling are deleted.