Re: Multiple DHCPed IPs on the same device

[Alexander Funcke <zaiberd@softhome.net>]

Hello,

Well the problem is that I'm a poor student with not so many NICs, so I'll
skip my extra 3 IPs if their isn't a way to tweak it non-costly.


//Alexander.


> A few days ago, I invited people to tell me why I was a fool for something I
> posted here, someone said they didn't think I was, so I'm going to try again.
> (I don't learn much when people agree with me, and I'm too new at OpenBSD to
> permit myself to think I am an expert!)
> 
> I don't think it is possible to do exactly what you are wanting to do -- have
> one NIC respond as multiple IPs using DHCP.  However, I bet you can accomplish
> what you want in other ways...
> 
> First, why I think what you desire to do is impossible:  DHCP (typically?)
> allocates IP addresses by machine name, or at least a machine name broadcast
> by the DHCP client software.  One card will only broadcast one machine name, I
> would think...
> 
> But there are probably other ways...
> 
> 1) Do you REALLY need DHCP?  *MOST* of the Cable Internet systems I have seen
> use DHCP for configuration, but the IP address(es) assigned to you is yours,
> and stays that way.  In other words, static addresses are often quite
> acceptable (This is NOT true for many DSL connections, apparently!).  There is
> some question in my mind as to whether or not you would really want to access
> a DHCP server outside your building -- it strikes me that it might be possible
> to do a "man-in-the-middle" interseption of all traffic in and out of your
> machine, but then, I might be full of it...  I'm also trying to remember how I
> set up one of my machines.  You see how scared of this I am 8-)
> 
> 2) Do you REALLY need FOUR IPs going through one machine?  If your system is
> like mine, you pay for each additional IP (about $8U.S. here, if you care).  I
> use my second IP for testing and configuration (although, I could probably
> live without it).  My second IP doesn't go through my OpenBSD box, it is kept
> separate for a different box/different applications.  NAT will give you as
> many IPs internally as you need.
> 
> 3) Multiple NICs in the one server.  I thought this was possible until I
> started researching it, now I'm not so sure, but you might be able to stick
> several NICs in the system, and have each one broadcast a different DHCP
> client name, and thus, each getting a different DHCP setting.  (I think this
> is where I might just convince people I am a fool 8-)  Of course, you would
> need a fifth card for your internal network, and now you have to find yourself
> a box which can actually handle FIVE network cards.  I think this is a pretty
> bad answer.
> 
> 4)  Multiple machines.  I've found OpenBSD runs darned well on very modest
> hardware, hardware that many of us have stacked up in the basement.  As
> inefficient as this may seem, this is the only thing which would make sense
> for my needs (i.e., I want to be able to pull something out, put something
> else in, and yet have my "work" port still 100% functional).  Not sure why you
> want four IPs, so I don't know how usefull/idiotic this suggestion is to you.
> 
> Hope this helps!
> NICk.
> 
> 
> Alexander Funcke wrote:
> 
> > Hi,
> >
> > I've got a OpenBSD box serving NAT to my LAN from a cable modem. The thing
> > is that my ISP gives me 4 IPs, but I don't want to have the cablemodem
> > connected directly to my LAN...
> >
> > So I wonder if their is someway to run dhcp multiple times on the same
> > device to use all the IPs?
> >
> > regards.
> > //Alexander Funcke
> 
> 
>