[Ns-bugs] [Bug 188] global routing does not handle ip aliasing

[code@nsnam.ece.gatech.edu]

http://www.nsnam.org/bugzilla/show_bug.cgi?id=188





--- Comment #19 from Mathieu Lacage <mathieu.lacage at sophia.inria.fr>  2009-02-03 08:24:45 EDT ---

(In reply to comment #18)
> > > I still get the feeling think these fake devices will be a source of confusion
> > > for people doing work on L2 stuff (like me).  We'll have to take extra care to
> > > check whether a device is real or fake before using it...  If you do it, I
> > > recommend to at least try to put it on a different layer, so that only layer >=
> > > 3 is affected and they do not appear in the list of Node devices
> > > (Node::GetDevice).
> > > 
> > 
> > It seems to me that these should not be in layer-3 but should appear to layer-3
> > like a real device.  For instance, it seems to me that loopback should be a
> > L2-virtual device rather than the way it is an IPv4 only device now.  I think
> > that people doing L2 work on 802.1q will probably want support for these types
> > of devices.

I believe that the reason why the ip loopback is implemented the way it is is
because of ARP which must not be used for this loopback device: Previously,
there was no NeedsArp method so, maybe that now that this method is here, we
can do what you describe. I am worried that this change could introduce very
subtle problems though.

> 
> You make a good point regarding 802.1q.
> 
> > 
> > But I agree with you that there are issues lurking with these types of devices
> > that need to be resolved so that they do not become confusing.  
> > 
> 
> One of the things that scare me is that this will probably mean we will need
> yet another IsLoopback () pure virtual method in the base class, or IsVirtual
> (), if we follow the current trend.  The number of IsXxx () methods in the base
> class is starting to grow too much IMHO.

If there is a need for yet another IsXXX method, this is a non-starter for me.


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