Dummy Network Interface

[ms419 at freezone.co.uk]

My apologies for such an undescriptive post.

I am trying to run a kerberos KDC on a mobile system. Unfortunately, 
the KDC won't bind to the loopback device, and all interfaces are 
disabled by the operating system when they are inactive - there is no 
link detected. So I am trying to configure a device with a private IP 
address, the only purpose of which will be to connect to the local 
machine.

On Jan 15, 2004, at 12:47 PM, Michael W. Oliver wrote:

> On Thu, Jan 15, 2004 at 03:07:20PM -0500, Robert Watson wrote:
>>
>> On Thu, 15 Jan 2004, Vlad Galu wrote:
>>
>>> |On Tue, 13 Jan 2004 ms419 at freezone.co.uk wrote:
>>> |
>>> |> How does one create a dummy network interface in FreeBSD?
>>> |
>>> |Dummy in what sense?  An interface where the packets are simply
>>> |dropped? if_tap and if_tun both provide pseudo-device in /dev that a
>>> |userspace process can attach to in order to emulate a network 
>>> interface
>>> |(used by VMWare, ppp, various tunneling bits, ...)  In the absense 
>>> of a
>>> |process sitting on the device, they simply drop the packets.  
>>> Although
>>> |they may get garbage-collected if unused on -CURRENT...  You can 
>>> also
>>> |use netgraph to bring pseudo-interfaces, perhaps without anywhere 
>>> for
>>> |packets to go.
>>> |
>>> |And, I suppose, create in what sense?  Are you looking at this from 
>>> a
>>> |developer perspective, or you just need one from a user perspective.
>>> |If writing a device driver (and hence needing a starting point), 
>>> if_tap
>>> |and if_tun are fairly decent models for a pseudo-interface.
>>>
>>> 	I think he could use the discard interface smoothly. On Linux
>>> (from which the dummy interface notion is taken from) it is simply 
>>> used
>>> for testing purposes, as in routing, or perhaps socket programming. I
>>> personally have used it for a while, but then I used interface 
>>> aliasing,
>>> which became a habit.
>>
>> Does the discard interface in Linux "act like" another type of 
>> interface,
>> such as point-to-point, ethernet, etc?
>
> I believe that he was referring to the discard interface in FreeBSD.  I
> don't know about Linux at all, but I have used the discard interface in
> a FreeBSD router much like a Null interface in a cisco router.
>
> pseudo-device       disc
>
> man 4 disc
>
> -- 
> Mike
> perl -e 'print unpack("u","88V]N=&%C=\"!I;F9O(&EN(&AE861E<G,*");'
>