[TriLUG] Re: Fixed or dynamic IP addresses? Dual IP addresses on same port?

[Jon Carnes]

You can set DHCP to modify the /etc/hosts file or you can run a script out
of rc.local that does this for you.  I used to do this all the time before
DHCP finally worked.

Jon
----- Original Message -----
From: "Scott G. Hall" <ScottGHall at BellSouth.Net>
To: <trilug at trilug.org>
Sent: Saturday, March 29, 2003 5:33 PM
Subject: [TriLUG] Re: Fixed or dynamic IP addresses? Dual IP addresses on
same port?


> Corey Mutter <mutterc at nc.rr.com> wrote:
>
> >On Fri, Mar 28, 2003 at 07:54:46AM -0500, Scott G. Hall wrote:
> >
> >
> >>I also have a router/switch acting as an Internet gateway, firewall, and
> >>DHCP server.  Currently all of the machines are configured to
dynamically
> >>get their IP addresses from the DHCP server on the router/switch.
> >>
> >>Now my dilemma: I want to startup FTP and HTTP servers on my private
LAN,
> >>as well as allow for the r* utilities (rlogin, rcp, etc) and NFS shares.
> >>Do I still want to use dynamic IP addressing?  Or do I need to switch
over
> >>to only static addressing?
> >>
> >>
> >
> >You can do both... most DHCP servers will allow you to configure things
so
> >that a particular machine (as measured by Ethernet MAC address) always
gets
> >the same address.
> >
> >
>
> The problem is this: when the Linux boxes receive their IP addresses
> dynamically, they experience the problem.  Without a hosts table, they
> cannot
> resolve their own name through gethostbyname(), much less find the others.
> This is preventing any FTP or HTTP server from running (and I assume other
> servers as well -- I'm going to add a local pop server to sort through
email
> retrieved rom boxes all over the 'net and also forwarded to us from our
> registered (unhosted) domain).
>
> What we did where I used to work, is that each machine that served up
> services had a static IP address and hostname for the service.  This was
> then maintained in a local hosts table that was then distributed to each
> machine via NIS.  Then any machine that was to act as a workstation was
> served by the DHCP server and received a dynamic address, but each
> maintained
> it own identity (hostname).  Therefore, there were some machines that
acted
> as both servers and workstations, with two hostnames, two IP addresses --
> one static, one dynamic -- and the workstation hostname (not the server
> hostname) was the dual-machine's primary hostname, and also the one used
> by the Lan Manager/Windows/SMB communications (various manger's
Windows-only
> boxes, and some Mac's; in fact the SMB sharing was the only way to pass
> files among various user's desktops directly).  All of the dual server-
> workstations used only a single physical interface, and had two
driver-level
> interfaces ARP'ed on them -- a static one and a dynamic one.
>
> >If your router/switch doesn't have that kind of config option, and you
> >deploy a dhcpd on a Linux-like machine instead, you can just add
something
> >like the following to dhcpd.conf:
> >
> >--- cut here
> ># Laptop docking station
> >host dock {
> >  hardware ethernet 00:c0:4f:ee:01:e3;
> >  fixed-address 192.168.1.4;
> >}
> >--- cut here
> >
> >Corey
> >
> >
>
> I was hoping to avoid using a PC as the DHCP server, because I take them
> down and reconfig them too often.  The LinkSys unit is on a battery backup
> with the ADSL modem and 16-port hub, so that network does not go down when
> the power goes out.  I was hoping to work out the dual solution.  However,
> since it is my home network, and noone in the Internet or elsewhere is
going
> to see it, and the hosts table is totally my own editing, and I just
reread
> the manual for the LinkSys unit for setting up VPN tunneling, I think I
may
> just go static IP's and be done with it.  After all, we are only talking
> about maintaining the hosts table for 9 machines (13 if you include dual-
> boots).  I still like the idea of dual-IP addresses for the one machine
that
> is spooling the 3 printers and will run the local HTTP and POP servers;
and
> for the other machine that is providing a ton of NFS shares (15
> harddrives --
> 3 SCSI cards).  I would like to separate the server and the workstation
IP's
> on these boxes.
>
> --
> Scott G. Hall,
> Raleigh, NC, USA
> ScottGHall at BellSouth.Net
>
>
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