How do I deploy correctly my DHCP Servers with DHCP Option 82?

Question

My Goal is to achieve a seperate DHCP Pool on my switches, how am I able to achieve it on a flat network hosted for a LAN-Party. Which means seperate VLANs should be avoided

We're talking about following settings:

• Network: 172.16.0.0/21
• 6x Avaya ERS 5500/5600 Switches
• Several Proxmox Machines

My endgoal is, that on

• Switch A, any DHCP Request get an IP from Pool 172.16.0.10 - 172.16.0.255

• Switch B, any DHCP Request get an IP from Pool 172.16.1.1 - 172.16.1.255

and so on ... But I'm scratching my head. What I read in the documentation was, that I have to setup an ISC-DHCPD which I'm telling the different pools. Then I setup on every Switch a DHCP-Relay that points to my ISC-DHCPD. And thats where my confusion starts:

That would mean that in that network would be more then one DHCP Server running which can lead to more trouble. My first Idea was, since that are L3 Switches to block any UDP 67 Communication except the Switches themself to talk to the main DHCP.

Would that be the correct way or do I overthink and it can be achieved easier? I would love to use the DHCP Server from my OPNSense, but I already read that this won't be possible :(

Answer 1

That would mean that in that network would be more then one DHCP Server running which can lead to more trouble. My first Idea was, since that are L3 Switches to block any UDP 67 Communication except the Switches themself to talk to the main DHCP.

No you have one DHCP server with multiple pools. Every switch is a DHCP relay for it's local subnet. The DHCP server is the ISC DHCP server, not the relays.

You should of course separate the networks at the switch level, so that the downstream and upstream ports are not in the same subnet. This can be done via for instance VLAN's. The switches will route traffic going to the upstream port.