[olsr-dev] Re: [OLSR-users] Same IP address for several interfaces

Ignacio García Pérez (spam-protected)
Wed Dec 1 17:17:44 CET 2004

> I think this is still valid. The idea is great for your special cases -
> but it will not work in the general case and it is not RFC compliant
> because the RFC states that IPs are the way to map interfaces on foregin
> hosts. If this is to work in the scenario where one might hear HELLOs from
> multiple interfaces using the same IP on a neighbor host then one has to
> know the ID of the remote interfaces. To do this one has to change the
> HELLO messages - needless to say, this breaks RFC3626 compliance...

I already though of that but didn't even mention it because changing the
HELLO format was not (and AFAIC will never be) an option.

My suggestion was more on the lines of identifying a hello not only by the
sender IP but by the pair (sender IP, receiving interface).

Besides the fact that the RFC states that IPs are the way to map interfaces,
what practical effect would have to use (sender IP, recv_iface) ?.

At a glance, it comes to mind a situation in which node A has two wireless
interfaces and node B has one. If a HELLO from B is heard by both interfaces
in A, it would be treated as two different HELLOs...

> This is to much of a special case to be included in the olsrd code IMO. My

I agree. I was just wondering a way to make it possible without breaking

> suggestin is that somone maintains a patch(I'll gladly link to it from
> olsr.org) or if you'd like, fork off a project of your own as implied on
> one of your earlier mails :-)

That's a lot of work, and I mean not implementation but testing work. Mesh
networks are difficult to test (in the sense that you see the problems
usually only when you deploy the real system), and the most important value
olsrd has to me is a fairly large user base. I, for one, cannot forego this
just to save a bunch of IP addresses :-)

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