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Re: [TCLUG:6694] virtual IPs

The easiest way to add aliases on redhat is to go into your
/etc/sysconfig/network-scripts directory, and copy ifcfg-eth0 to
ifcfg-eth0:[0...256]. Then, just edit the script and change the interface
name and ip/gateway/etc. Of course, sometimes it works better just to edit
/etc/rc.d/init.d/network and add the commands that Chewie gave you below.
You could also add them to /etc/rc.d/rc.local, but you can run into
problems doing this because your daemons are started before the interfaces
are initialized (rc.local is the last thing to run), and they may not
recognize the new interfaces.

Nate Carlson
the infinite loop

On Wed, 23 Jun 1999, ^chewie wrote:

> > Quoting Tim Wilson (
> > > Hey *,
> > > 
> > > I'm trying to set up my Web serve with virtual IPs for hosting multiple
> > > schools' Web sites. I know that the 'ifconfig' command is used for
> > > configuring network interfaces (although the exact syntax is rather
> > > complicated). I need to know where I would put the commands for starting
> > > up the interfaces. Would the series of ifconfig commands go in
> > > /etc/rc.d/rc.local? Somewhere else? BTW, this is a RH6 system.
> It isn't actually that difficult.  I did it in a matter of a couple
> hours to learn how to set up Apache, reading docs and compiling the
> kernel to do IP Aliasing.  The ifconfig is simple...
> 	# ifconfig eth0 netmask
> 	# ifconfig eth0:0 yyy.yyy.yyy.yyy netmask
> 	# ifconfig eth0:1 zzz.zzz.zzz.zzz netmask
> routing is also simple...
> 	# route add -host yyy.yyy.yyy.yyy eth0:0
> You add these in the same script that initializes your network card
> when you boot.  In debian, the script is called /etc/init.d/network.
> I'm not sure what it is in RH, but I'm pretty sure you can find out
> where by doing a grep for ifconfig...
> 	# grep ifconfig /etc/rc?.d/*
> Find out which link file it is and follow it to its source.  If you
> don't find it in the rc?.d directories, check your rc.boot or similar
> rc directory.
> On Wed, 23 Jun 1999, Bob Tanner wrote:
> > Do you need multiple ips? I'd recommend using virtual hosts under apache, you
> > use only 1 IP and let apache handle the virtualness.
> > 
> > I do not know how many hosts you want to offer, but there is a little in the
> > kernel on open file descriptors, which I ran into before I went with apache
> > virtual hosting.
> > 
> >
> It depends on your need.  If you need to do virtual domain name
> serving, you may be forced to use IP Aliasing.  But as Bob said, you
> can do Name based virtual hosting instead of IP based virtual hosting.
> Or you can use a combination of both.  Apache is very flexible...  If
> you've installed apache from packages, you've probably also installed
> the Apache manuals with it.  Check out your manual pages on your
> local Apache Server...  http://<hostname>/doc/apache/manual
> Either way you look at it, you'll have to maintain a DNS entry for
> each web site you host.  They can be any number of A or records
> pointing to the same IP with different names, or they can be different
> IP's that are aliased to your interface (eth0, eth0:0, eth0:n).
> There is an advantage to having different IP's that I'd like to point
> out.  DNS reverse lookup.  It's a lot cleaner when you have one IP per
> web site.  I know DNS understands multiple A records for one namespace
> (multiple records...just try an nslookup or
> any other well known mirrored web site).  I'm not sure if DNS
> understands how to resolve names when they're bound to one IP.  Does
> it give you a list of possible names to match?  I.e.,
>,, etc...?
> ^chewie
>  <<--- Check it out!  I'm selling my truck!
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