Re: Ether-tokenring routing

[Wim Dumon <Wim.Dumon@kotnet.org>]

Quoting Monz (monz@danbbs.dk):
<snip all kind of nice drawings and explanations>
> Anyway, to the real issue.
> A while ago, someone on our user group discussed bridging between Ethernet and
> TokenRing. I think this was turned down due to differences in the MAC layer; but
> today, at work, I was told it's at least posible to route ether-token on NT,
> because that functionality lies in the data link layer.
> 
> Not being an expert in protocols, I'm confused. Someone shed a light, please.
> What can be done with Linux (NT/Netware for that sake):
> Bridging, routing or IP-forwarding between ethernet and tokenring?
> 
Routing is possible, ip-forwarding too (but less interesting), bridging is
theorethically possible, but I don't know wether Linux accepts ethernet-
tokenring bridging (never realy tried it).  Our university lab is equiped
with both tr and ethernet, a linux computer with an ethernet card as well
as a tr card acts as a router between the two nets.
How you'd best do the routing depends on your situation, but we are using
proxy arp entries to make it look as if the tokenring net is on the ethernet
segment.  This is required because the router to the internet does not know
about the tr subnet.  This makes the setup quite messy, but it works.  We
could even add a second router and use dynamic routing protocols (probably
RIP) to make the thing nicer and more failproof.
If you can do routing, or even bridging, then forget about IP forwarding
(I suppose you mean port forwarding by this) since it is utterly uncool
and a lot of applications will stop working.  Bridging should be the
most transparant solution.

> A bit of protocol tech stuff on the subject would be appreciated.
Routing between tr and ethernet is realy just like routing between ethernet 
networks, but you have to set routes to tr* instead of eth*.  And this 
isn't even required when you use linux 2.2, since these routes are added 
automagically :-)
Bridging is done at the link layer, and was almost invented for cases like
mine.  Offcourse, you loose some features when you bridge.  eg IIRC, tr
provides a certain qos system, but ethernet doesn't so when you use a
bridge in your network you'll loose this functionality for connections
that travel over the bridge.


Cheers,
Wim.

-- 
Wim Dumon               KULeuven student
wimpie@kotnet.org       Linux !   3dom !
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