Re: Tranparent bridge

[Paul Robertson <proberts () patriot net>]

On Tue, 23 Sep 2003, Tony Rall wrote:

> Sorry for the digression, but aren't all bridges supposed to be 
> transparent?

Nope, you can build a non-transparent bridge if you want.  It helps the 
drivers in the cars see where... nahhh...

A non-transparent bridge will modify the MAC address of the 
packets as it bridges them between networks, a transparent bridge will 
forward all the layer 2 traffic unaltered.  The right combination of proxy 
arp and forwarding might technically make a non-transparent bridge (if 
you did all the broadcast/multicast stuff too.)  The main advantage would 
be in having smaller ARP tables at each node.

These days, I think the transparent is mostly in there to distinguish it 
from source route bridging.  In SRB, the route is added by the device into 
the token-ring frame (well, you can do the explorer thing, but I've never 
seen a network set up that way.)  

Generally SRB was used to take SNA over an intermediate network between 
two token ring LANs.  

Paul
-----------------------------------------------------------------------------
Paul D. Robertson      "My statements in this message are personal opinions
proberts () patriot net      which may have no basis whatsoever in fact."
probertson () trusecure com Director of Risk Assessment TruSecure Corporation

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