howto build a loopback connector

[Michael Drum <drum@she.de>]

Hi,

My problem is: I want to build a linux router with a token ring and an
ISDN interface, but I have no token ring network to test it. So the kernel
melds tr0: unrecoverable error: error code=0011, while no network is
connected (it' an IBM Auto 16/4 Adapter) 
So, in the token-ring-mini-howto a loopback connector is mentioned. Is there
a tutorial, how to built such a connector or could someone give me some
hints?

With best regards
  Michael

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