Authenticate systems before getting a DHCP IP?

Does anyone know how to authenticate systems or users prior to give them a DHCP IP?
If so, can you please let me know what product will give me this capability?

Thanks,
/Kyle

Kyle Lai, CISSP, CISA
KLC Consulting, Inc.
617-921-5410
klai@klcconsulting.net
www.klcconsulting.net

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