[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 #15 from Tom Henderson <tomh at tomh.org>  2009-01-31 11:50:21 EDT ---
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.

- 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)


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