Re: disabling ethernet loopback device completely

[salman h <salman_debian@yahoo.com>]

 David (and everyone else),

Thanks. I think this is pretty much what I am going to
end up doing. Basically pinging from one interface at
a time to a remote machine and doing the mactab magic.
This is also what Robert had suggested earlier. 

For future reference, there is a kernel patch
available that supposedly allows packets to be put on
the wire to allow external loopback in a situation
such as mine.
Here is the link to the patch:

http://www.ssi.bg/~ja/#loop 
(click on send-to-self)

I'll be happy to hear other suggestions.

So here's what I've probably learned today:

1. external loopback is not possible unless you want
to patch your kernel to change the behaviour of the
TCP/IP stack. Great, but if you're using your own
mutated debian kernel, then it's just one more patch
you've got to worry about. I'm not a fan of "patch"
jobs.

2. the bigger issue: the kernel doesn't necessarily
make an effort to distinguish the motherboard NIC from
NICs on a PCI card. So when I end up replacing a
customer's dual nic pci card in the field, and
suddenly what used to be eth2 is eth0 and eth1 is now
eth2 and eth2 is now eth0, it can cause a lot of
agony.

3. ???

Thanks,

Salman

--- David Mandelberg <mandelbergd@eth0.is-a-geek.org>
wrote:

> salman h wrote:
> > and while it disables the loopback interface, data
> > packets are still not being put on the physical
> > network.
> I don't know if this works, but you might as well
> give it a shot:
> 
> while read dev x; do
>  case "$dev" in
>   eth*)
>    dev="`echo -n "$dev" | sed 's/:.*$//'`"
>    ifconfig "$dev" 192.168.0.1 netmask 255.255.255.0
> broadcast 192.168.0.255
>    ifconfig "$dev":1 192.168.0.2 netmask
> 255.255.255.0 broadcast 192.168.0.255
>    ping 192.168.0.2 -I "$dev"
>    # do magic mactab stuff here
>    ifconfig "$dev" down
>    ifconfig "$dev":1 down
>    ;;
>   *)
>    :
>    ;;
>  esac
> done < /proc/net/dev
> 

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