[nos-bbs] Device alias IP addresses

Jay Nugent jjn at nuge.com
Wed May 23 13:57:26 EDT 2007


On Wed, 23 May 2007, Maiko Langelaar (ve4klm) wrote:

> Hi Mitch,
> > I can tell you all that I have exhausted my printed manuals, and have
> > carefully searched the Fedora documentation set for the answer ...
> According to an FAQ I found :
>     IP Alias is standard in kernels 2.0.x and 2.2.x, and available as
>     a compile-time option in 2.4.x (IP Alias has been deprecated in 2.4.x
>     and replaced by a more powerful firewalling mechanism.)
> That essentially says you won't find it in more recent linux distros,
> not by that name anways. IP Aliasing has been *replaced* with :
>     iproute2 and iptables
> Some worthy information that I managed to find on the topic is below :
> 1) You can learn some about it at lartc.org or other such sites.
> 2) I don't know what he means by "more powerful _firewalling_ mechanism"
>     but iproute2 package which replaces whole family of ifconfig/arp/route
>     commands, gives you a neat and more straight forward way of dealing
>     with the IP aliasing.

    What Skip is looking for is "ethernet aliases", that is, when a single 
ethernet interface can support multiple IP addresses.

   See:  man ifconfig

       The name of the interface.  This is usually a driver name followed 
       by a  unit  number, for  example  eth0  for  the  first Ethernet 
       interface. If your kernel supports alias interfaces, you can 
       specify them with eth0:0 for the first alias of eth0. You can use
       them to assign a second address. To delete an alias interface use 
       ifconfig eth0:0 down.  All aliases are deleted, if you delete the 
       first (primary).

   For example:  Skips first (or primary) IP assignment for eth0 on his
Linux box may be something like  To add a 44-net address to
this same eth0 interface he would need to issue the comand:

   ifconfig eth0:2

   To confirm that BOTH interfaces are indeed ifconfig'ed correctly, 
simply issue the command 'ifconfig':

# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:10:DC:38:FA:D9
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::210:dcff:fe38:fad9/64 Scope:Link
          RX packets:7635144 errors:5 dropped:0 overruns:0 frame:0
          TX packets:3128053 errors:0 dropped:0 overruns:0 carrier:0
          collisions:15567 txqueuelen:1000
          RX bytes:1384136412 (1.2 GiB)  TX bytes:232378712 (221.6 MiB)
          Interrupt:177 Base address:0x2000

eth0:2    Link encap:Ethernet  HWaddr 00:10:DC:38:FA:D9
          inet addr:  Bcast:  Mask:
          Interrupt:177 Base address:0x2000

   Add a route from your JNOS box to your Linux workstation (route add eth0) and then add a route on Linux to push all
traffic towards your JNOS box, and your Linux box is now a workstation on
the AMPRnet! :)

      --- Jay

P.S. Skip, wb8rcr.ampr.org is down right now.  So if you are testing to 
     see if you can pull his webpage and weather maps via the AMPRnet, ya 
     might wanna try again when his node is back online.  

"Getting rid of terrorism is like getting rid of dandruff.  It cannot
 be done completely no matter how hard you try." -- Gore Vidal
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