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Azure Networking Blog
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Custom DHCP support in Azure

cynthiatreger's avatar
cynthiatreger
Icon for Microsoft rankMicrosoft
Mar 19, 2024
Dynamic Host Configuration Protocol (DHCP) is a network protocol used to dynamically assign IP addresses and other network parameters to devices on a network.         HOW DHCP WORKS ...
Updated Aug 05, 2024
Version 5.0
virtual network
Toivo's avatar
Toivo
Copper Contributor
Jan 29, 2025

Looking at a packet capture from a Windows 11 PC, the DHCP Discover appears to be port 68 > 67, the offer (from a DHCP server VM in Azure) is 67 > 68, the request is again 68 > 67, and ack is 67 > 68. 

So apparently the source port is different between the unicast from client and unicast from relay, that's not super clear from the diagram. I.e. the relay changes the source port of the broadcast REQUEST when it gets relayed as unicast.