Re: dhclient vs aliases

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 <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