Disabling DHCP in secondary NIC also disables DHCP on primary NIC - Why?

TrueNAS General
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Hello,

I am running TrueNAS Scale vDragonfish-24.04.2.

My motherboard has two physical ethernet interfaces (eno1, eno2). I installed Scale with only my primary interface connected (eno2). Today, I am setting up the secondary interface (eno1) to be used by my VMs, per the following instructions:

  1. Accessing NAS From a VM | TrueNAS Documentation Hub
  2. Managing Interfaces | TrueNAS Documentation Hub

First, I see this comment, which I don’t understand: “You can use DHCP to provide the IP address for only one network interface and this is most likely for your primary network interface configured during the installation process.” Why would that be? I do use static IP addresses almost exclusively, but I prefer to set those at the router and leave clients on DHCP so I can control IP addresses from one source. Why can’t eno1 and eno2 both use DHCP?

I’m trying to set up eno1 by unchecking DHCP (because the instructions say only one interface can use DHCP and I want eno2 to use DHCP). However, as soon as I save that change, this also unchecks DHCP from eno2. Why? Why can’t I configure eno1 without it messing with the settings for eno2? I am very confused.

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Further, even though both interfaces are on DHCP (because it wouldn’t allow me to uncheck DHCP on only one itnerface), everything seems to be working fine despite the documentation saying you can’t do this.

I’ve rebooted the device and assigned eno1 to my VM. The VM has an internet connection and I’m still able to get to the web UI. I’m not sure what to make of all of this.

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I demonstrate the issue in this video

I suspect your VM is communicating with your NAS via the network. Which is fine if that’s what you want. It may also be hairpinning in the NIC.

Executing the iPerf test I demonstrate will show the actual bandwidth achievable.