Which Dell switch models will you be using for VoIP networking?  

LLDP is a layer 2, vendor-neutral protocol used by network devices to identify themselves and their capabilities to neighboring devices on the network. Dell Techcenter has several documents that discuss LLDP and how it is used with VoIP.  Here are links to three good docs that should get you started in the right direction:

http://en.community.dell.com/techcenter/networking/m/networking_files/20440970 

http://en.community.dell.com/techcenter/extras/m/white_papers/20439292.aspx

http://en.community.dell.com/techcenter/networking/m/networking_files/20443970

The third one in particular has some great insight to how LLDP is used to identify devices connecting to the network.  Appendix B might be of particular interest to you.

Hope this helps!

-B

delete please

The three documents should provide good examples and commands to use for the N3000 switches (and all other Dell EMC N-Series switches) on your network.  You should be able to consult the User Guide to find the LLDP information and commands for the other switch in question.