isc dhclient not appling alias to interface

Theodore Wynnychenko tmw at
Wed Sep 21 21:30:17 UTC 2016

I am looking at replacing the base dhclient in OpenBSD with the isc-dhcp-client
available in OpenBSD's packages.

The primary reason for this is to take advantage of having an alias ip address
assigned to the interface.

But, I can't seem to figure out how to get this done.

I don't know why, but I can't get the isc-dhcp-client to assign an alias to the
interface, despite the documentation that states it should.

This is being run on OpenBSD current.

The isc dhclient available is 4.3.4

# /usr/local/sbin/dhclient --version

I have created an /etc/isc-dhclient.conf file:
timeout 60;
retry 60;
reboot 10;
select-timeout 5;
initial-interval 2;
script "/usr/local/sbin/dhclient-script";

supersede domain-name "";
supersede domain-name-servers d.n.s.1,d.n.s.2;

request subnet-mask, broadcast-address, time-offset, routers;

alias {
  interface "em0";
  fixed-address fi.xed.ip.addr;
  option subnet-mask;

But, after killing the running dhclient process (included with OpenBSD's base
installation), removing the leases at /var/db/dhclient.leases* and starting
isc-dhcp-client with:

# /usr/local/sbin/dhclient -cf /etc/isc-dhclient.conf em0

The isc client is able to get an offer from the dhcp server:

Sep 21 16:18:05 xxx dhclient: DHCPDISCOVER on em0 to port 67
interval 2
Sep 21 16:18:05 xxx dhclient: DHCPOFFER from
Sep 21 16:18:10 xxx dhclient: DHCPREQUEST on em0 to port 67
Sep 21 16:18:10 xxx dhclient: DHCPACK from
Sep 21 16:18:10 xxx dhclient: bound to -- renewal in 111100

However, the alias does _not_ get assigned to the interface.  The only address
is the dynamically assigned one.

According to the dhclient.conf man page, "the dhcp client can be set up to
configure an IP alias using the alias declaration."

I understand this to mean that the alias declaration above should result in the
interface being configured with both the dynamically assigned ip address, and
the fi.xed.ip.addr given in the alias declaration of my isc-dhclient.conf file.

But this is not happening.  I can find no guidance on what I am doing wrong, and
why the isc-dhcp-client is not assigning the alias.

Thanks for any advice.


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