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DHCP client identifier

As explained in Acing the CCNA Exam: Volume 2 Advanced Networking and Security

A DHCP client identifier is a value that uniquely identifies a DHCP client to the server.

A DHCP client identifier uniquely distinguishes one DHCP client from another. The client normally sends it in DHCPDISCOVER and subsequent messages, allowing the server to associate leases with clients. section 4.1.2

Cisco IOS displays the identifier in the Client-ID/Hardware address/User name column of show ip dhcp binding. A common Ethernet format adds prefix 01 to the interface MAC address; MAC address 5254.0017.2fda appears as 0152.5400.172f.da. section 4.1.2

Reading a DHCP binding

In show ip dhcp binding, 10.0.0.6 paired with 0152.5400.172f.da means that client leased 10.0.0.6. The identifier may resemble a MAC address, but the leading 01 is part of the client-ID format. section 4.1.2

How Acing the CCNA Exam: Volume 2 Advanced Networking and Security covers it

How deep it goes
Explains DHCPDISCOVER behavior and one Ethernet format, but defers other client-ID formats beyond CCNA scope.
Examples
Uses Cisco IOS show ip dhcp binding output containing 0152.5400.172f.da and 0152.5400.1792.08.
What it assumes
Assumes basic DHCP and MAC-address knowledge while defining the client identifier and its purpose directly.
What you can do after
Evaluate Cisco IOS DHCP bindings by interpreting the client-ID column and recognizing a common Ethernet identifier format.
How it connects
Connects DHCP client identifiers with DHCP servers, DHCPDISCOVER, MAC addresses, and DHCP bindings.
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Related concepts

This explainer was generated by Manning's knowledge graph from the text of Acing the CCNA Exam: Volume 2 Advanced Networking and Security. The section links point to the parts of the book it draws on.