Re: dhclient vs aliases

Re: https://forums.freebsd.org/threads/dhclient-trashing-alias-ip-address-upon-reconnect.58729/

You can use a dhclient.conf(5) entry like this to guarantee that the
alias is re-applied every time the interface gets a new address from
DHCP (or the old lease is re-applied):

Code:

          alias {
             interface "em0";
             fixed-address 10.0.0.3;
             option subnet-mask 255.255.255.0;
           }

On Mon, Jun 9, 2025 at 10:20 AM Andriy Gapon <avg@freebsd.org> wrote:
>
>
> Apologies if this is a FAQ and maybe it has always been like that but I've just
> noticed this.
>
> A switch needed to be rebooted, so on a FreeBSD host a link went down and then
> up on an interface connected to the switch.
> Apparently triggered by those events, dhclient decided to renew the interface's
> IP address. Afterwards, all alias IP addresses on that interface were cleared.
> Just in case, the new IP address was exactly the same as the old IP address
> (it's "hardwired" in the DHCP server configuration).
>
> This was unhelpful because the host runs a number of jails with a simple IP
> configuration via aliases.
>
> --
> Andriy Gapon
>
>


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