VNET/epair double MAC address

Marlon Leerkotte marlon at
Sun Feb 12 15:28:39 UTC 2017

Hi everyone,

I have been using jails with VNET since about 10.1 or 10 and have so far not encountered any huge problems except for accidentally giving two jails the same epair which broke my stack. But today I did encounter a problem.

The problem i encountered was where one of my jails would lose all connectivity when starting another jail, after some investigation it turned out that both jails had the same MAC address. I’m not aware of how these MAC addresses are generated but this seems to be a bug, as I’m not manually assigning MAC address.

In the attachments you will find my jail.conf and the ifconfig output of both jails.
I hope someone can help me with this and/or give me some insight as to how the addresses are generated.


Marlon Leerkotte

M.R. Leerkotte
Mail: marlon at <mailto:marlon at>
LinkedIn: <>

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