arpwatch and truenas are complaining that the IP of my unraid server is flapping between the MAC of its eth0 (one of 4 interfaces, but eth1-3 are not used) and vhost0@eth0. And from all I know about IP networking having two interfaces with different MACs using the same IP is not a good condition. I have investigated a little and it looks like vhost0@eth0 is there even if docker is off, but then it has no IP assigned. If I turn docker on, it gets the IP of eth0 assigned. (VM manager is using virbr0, which uses a different IP and also goes away when turnin VM manager off) The curious thing is that vhost0 hast a routing metric of 0 and is thus preferred over eth0 (metric 1007). Such a construct is unseen on all of my Debian docker hosts, so it is certainly possible to have docker working fine without such a unsane setup. Is it possible to run unraid with docker in a way that each interface has an on IP (without assigning individual non-docker-network IPs to the containers), and how?

I investigated further wit different settings for Docker and I found that vhost0@eth0 will only then get an IP (and then it is the same IP as eth0) if both of these are enabled (if only one of these is enabled, vhost0 does not get an IP): Host access to custom networks IPv4 custom network on interface eth0 (optional) I have no ides why both were enabled on my server (and it is quite possible I did this myself without knowing what I was doing). Just to clarify whether I really need those, could someone confirm or correct my assumptions: IPv4 custom network on interface eth0 (optional): I only need this, if I want to have a containter to use an IP from the subnet in which the IP of eth0 is located. Correct? Host access to custom networks: I only need this if the unraid host should access a service provided by some of the containers running on the the unraid host. Example an agent running natively on the unraid host needs to connect to a service (like NMS or backup) in a container. Correct?

vhost0@eth0 is using the same IP as eth0 -> this is an IP collision, how to do better?

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Solved by murkus

March 7, 20242 yr

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November 26, 20241 yr

Yes, please help us understand why Unraid seems to be different from every other VM platform. I've run VMware servers and barebones Docker boxes, and I have never seen a situation where an IP is duped with a different MAC. To this day, I still have a duped IP in my Unifi, and I've managed it by flagging it as blocked. Everything works, so it's not as if it is having any impact on functionality. But it does impact things when that MAC is not blocked. I've seen services become flaky and unreliable. It makes sense that packets could be routed to the wrong network port/MAC.

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vhost0@eth0 is using the same IP as eth0 -> this is an IP collision, how to do better?

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