[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


Tom Henderson <tomh at tomh.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED




--- Comment #21 from Tom Henderson <tomh at tomh.org>  2009-04-21 00:17:25 EDT ---
(In reply to comment #15)
> I've been looking at this bug again in the context of the ns-3-ip work. 
> AFAICS, there is no support in the real world for routing protocols to deal
> with IPv4 aliasing on a single net device.  Instead, how this seems to be
> universally handled is the creation of virtual devices on top of a physical
> device.  These are often called subinterfaces in routers.
> 
> Since global routing is a port of the quagga OSPFv2 implementation, which
> cannot handle multiple IP addresses AFAICS (but could handle virtual devices),
> I am currently thinking that the right way to handle this is:
> 
> - do not try to support global routing for multiple Ipv4 addresses on a single
> Ipv4Interface/NetDevice.  We can allow such configuration, but the global
> routing code should print out a warning at NS_LOG_WARN level when it encounters
> a multiply-addressed Ipv4 interface, and just use the first address (index
> zero) in such a case.  I believe that trying to support properly lots of IP
> addresses on a single interface will just make the code very complicated, and
> is low priority IMO compared to other things.

I added several such statements in the global routing code; e.g.

NS_LOG_WARN ("Warning, interface has multiple IP addresses; using only the
primary one");

> 
> - we should instead encourage some development of virtual net devices for ns-3.
>  This might make a good GSOC or student project.  The global routing should
> then support virtual net devices for this IP aliasing functionality (like in
> the real world).  Virtual net devices may also be useful for other scenarios,
> such as vlan tagging, channel bonding, and ad hoc routing.
> 
> - downgrade this bug to P3 (waiting for virtual net device)
> 

I'm marking this as FIXED, in the absence of a virtual net device (the code
will log warnings, as I suggested earlier).  When we get virtual net devices,
we will need to make global routing work with them or else file a new bug on
that topic.


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