LLDP is an open standards based equivalent of CDP. It is also known also as 802.1AB. If a non Cisco IPT solution is being implemented it may be necessary to configure LLDP-MED. Non Cisco IPT solutions traditionally used DHCP as the mechanism for the phone to discover which voice VLAN is to be used. Cisco IPT solutions use CDP. If the non-Cisco voice solution is designed to use LLDP then LLDP requires to be enabled on the end-user ports. The decision to use LLDP is part of the IPT design. It’s important to confirm with the IPT designer which method (DHCP or LLDP) is being used to assign the voice VLAN information to the IP Phone, to confirm whether LLDP is required. Over time it is expected that more non Cisco solutions will use LLDP as it prevents the need for large DHCP scopes.
For a detailed comparison of LLDP-MED and CDP, see the following link:
LLDP removes the need for a non-Cisco IP phone to use DHCP to discover the voice VLAN, using the LLDP-MED network-policy profile type, length & value (TLV) to specify the values for VLAN, class of service (CoS), differentiated services code point (DSCP), and tagging mode. Additionally LLDP-MED can be used to negotiate lower power (e.g. 4W instead of 7W for a Nortel IP phone 2004 with appropriate firmware which supported LLDP-MED (NTDU92)).
Simply configuring the user port for the relevant Nortel/AVAYA IPT (with voice and access VLANS, relevant qos service policy etc), as usual, and then enabling LLDP should be sufficient in most cases to support non-Cisco IP Phones. Please refer to the QoS documentation for details of the LAN QoS configurations for non-Cisco IP Phones.
By Alok : CCIE #42872