On Mon, Jun 9, 2025 at 10:40 AM Andriy Gapon <a...@freebsd.org> wrote:
>
> On 09/06/2025 17:26, Paul Procacci wrote:
> > 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;
> > }
>
> Thank you!
> This should work, but it kind of kills a "single source of truth" for jail
> configurations.
>
> So, it seems that there is a quirk regarding jail+aliases and DHCP.
>
> > On Mon, Jun 9, 2025 at 10:20 AM Andriy Gapon <a...@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
I haven't personally tested this, but does something akin to the following work?
ifconfig_em0_alias0="DHCP"
ifconfig_em0_alias1="DHCP"
Assuming you're using dhcp addressing for single source of truths then
give this a whirl perhaps.
~Paul
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