LLDP and CDP parameters for IP phones using RADIUS attributes
If the switch receives an attribute that identifies the incoming client as a voice or phone device, Link Layer Discovery Protocol (LLDP) and Cisco Discovery Protocol (CDP) protocol information are automatically configured. LLDP and CDP advertise the VLAN information so that the client connected to the port learns the voice VLAN. CDP does not require any specific information, whereas LLDP requires differentiated services code point (DSCP) and priority values to configure the Media Endpoint Discovery (MED) policy.
Attribute for RADIUS to identify the client as phone device
DSCP and priority values can be specified optionally in the attribute; otherwise, default values of dscp (46), and priority (5) are applied. The following options can be specified through the "Foundry-Voice-Phone-Config" attribute.
Valid syntax for the "Foundry-Voice-Phone Config attribute"
| Syntax | Meaning |
|---|---|
| " " (double quotes separated by a space) | application: voice, DSCP: 46, priority 5 (default) |
| "dscp:40; priority:4" | application: voice, DSCP: 40, priority: 4 |
| "appl: video-conference; dscp:30" | application: video-conference, DSCP: 30, priority: 5 |
| "priority:7" | application: voice, DSCP: 46, priority: 7 |
In previous releases, if the attribute "Foundry-Voice-Phone-Config" is not returned in the RADIUS response, no DSCP or priority info is provided to the phone via LLDP/CDP. In FastIron release 08.0.70c and later releases, the switch sends default values (DSCP 46 and priority 5) as the FastIron device detects phones via LLDP or DCP, even when the "Foundry-Voce-Phone-Config" attribute is not present. This further reduces the configuration needed for phones since, in most cases, the Foundry-Voice-Phone-Config VSA need not be configured on the RADIUS server to achieve the desired result.