Re: dhcp and dual-homed filtering host

["Jens B. Jorgensen" <jjorgens@bdsinc.com>]

I have a similar setup. You just need to tell dhcpd which ethernet interface you want
to serve up IPs for. This can be done by editing /etc/init.d/dhcpd. Here's the changes
I made:

helios$ diff -c /etc/init.d/dhcpd~ /etc/init.d/dhcpd
*** /etc/init.d/dhcpd~  Tue Feb 25 20:05:56 1997
--- /etc/init.d/dhcpd   Fri Jul  2 21:17:21 1999
***************
*** 14,20 ****
    start)
      if [ $run_dhcpd = 1 ]
      then
!       start-stop-daemon --start --verbose --exec /usr/sbin/dhcpd
  # This route is required for some Operating systems to understand
  # dhcp replies
        route add -host 255.255.255.255 dev eth0
--- 14,20 ----
    start)
      if [ $run_dhcpd = 1 ]
      then
!       start-stop-daemon --start --verbose --exec /usr/sbin/dhcpd -- eth0
  # This route is required for some Operating systems to understand
  # dhcp replies
        route add -host 255.255.255.255 dev eth0


Marc Haber wrote:

> Hi!
>
> In a lab network, I have a dual homed Debian host that should act as a
> packet filter between the external ("untrusted") and the internal
> ("trusted") interface. The untrusted network is on eth0; the trusted
> network on eth1. The host should assign IP numbers on the trusted
> network via DHCP while not doing so on the untrusted network.
>
> The Package description for dhcp-1.0.2-0.1 says: "This package only
> supports DHCP IP assignment on one interface." So, this is fine with
> me.
>
> I proceed to install dhcp and created an /etc/dhcpd.conf with only a
> single subnet statement for the trusted network. When I try to start
> the dhcp daemon, I get the error message "No subnet declaration for
> eth0 (192.168.130.38)", the IP being the one of the external
> interface.
>
> When I add an empty subnet declaration ("subnet 192.168.131.0 netmask
> 255.255.255.0 {}") to /etc/dhcpd.conf, I get "The standard socket API
> can only support hosts with a single network interface", which is
> substantially different from the restriction the Package file
> mentions.
>
> Am I missing something? How can I get this dhcp into business?
>
> Greetings
> Marc
>
> --
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--
Jens B. Jorgensen
jjorgens@bdsinc.com