Private in-house domain

[Paul Lussier]

"Tech Writer" <TechWtr at handspun.com> writes:

> Andrew and Stephen,
>
> Thanks for the tips!  Your combined suggestions seemed to do the trick.  I 
> edited my rc.local file and added the lines:
>
>     echo "Set up IP alias interfaces"
>     /sbin/ifconfig eth0:0 192.168.1.30
>     echo "Set up routes"
>     /sbin/route add -host 127.0.0.0 dev eth0
>     /sbin/route add -host 192.168.1.1 dev eth0
>     /sbin/route add default gw 192.168.1.1
>
> Now eth0 has the IP address 10.25.1.10 that I assigned, and also has an 
> alias of the IP address 192.168.1.30 that my Linksys wants to talk to.  The 
> routing table uses the IP address of my Linksys router, and I can now 
> successfully get nslookup responses outside my private mini-domain and my 
> web browser can see the rest of the world, too.

Hi Peg,

Though this "works", I think it's taking the wrong approach.  What
you've done is hacked a file to set something up through brute-force
as a work-around to the correct way of configuring the network for
this host.

Granted, this is your home environment, and therefore the "normal
rules" of "proper network management" may not apply.  However, by not
applying and following said "normal rules" you've cirumvented your
learning experience and now only understand how to use this
brute-force method.  This is both inelegant and ulitmately
unmaintainable.  Additionally, it's non-trasferrable to the "real
world" (maybe that doesn't matter, I don't know).

RH, CentOS, etc. all have a "proper" means of configuring the network.
Hacking the rc.local script isn't the way to do it.

If what you're really after is a single NIC on multiple networks, then
configure a proper ifcfg-<interface> file for the NIC alias.  This
file will take all the standard key=value pairs of a normal interface
and properly set up the routing tables for you.

Googling for 'CentOS ifcfg interface aliases' resulted in 915 hits for
this combination, the 2nd return on the very first page is the exact
documentation you need to set up an alias ifcfg file for CentOS.

Using the correct configuration files to set this up also has a number
of advantages vs. the hack to rc.local:

 - if you ever add another physical NIC to the system in question,
   it's a matter of simply renaming a file vs. remembering where this
   configuration is, then hacking the file to reflect the correct
   interfaces and routes.

 - if you want to temporarily turn off the 10.x network, it's a matter
   of ifdown'ing the interface, which will also take care of removing
   all the routes for you.  ifup'ing the interface will re-configure
   them for you.  As it is, you can set things up, but tear them down.

 - The lines above, though they work, don't look correct to
   me. (i.e. there is no host 127.0.0.0, that's a network, and
   probably should be using a -net option.) Properly written config
   files set things up correctly and remove human error and the
   guessing that goes with being unsure.

-- 
Seeya,
Paul