Power Over Ethernet Interoperability Guide

IEEE 802.3at Table 33-8 Explained Further

Table 33-8 on Page 42 of 802.3at-2009 summarizes some of the above-mentioned points cogently. This figure was reproduced in Fig. 4.1 with adjoining examples revealing how it should be understood and interpreted. The key conclusions are (for compliant PSEs and PDs):

1.  A Type 2 PSE is allowed to depend only on 2-finger classification to seek out Type 2 PDs, with no layer-2 /LLDP classification. But it can also opt to use 1-finger classification followed by LLDP classification. So when the data link comes up, the PSE will use LLDP protocol to communicate with the PD that it is a Type 2 PSE and is thus able to provide more than 13 W to it.

2.  A Type 2 PD must be able to accept both of the above Type ...