Re: help


Charles Hedrick (hedrick@aramis.rutgers.edu)
Sun, 22 Nov 87 00:00:28 EST


The author describes a configuration having a mix of vendors, administrators,
and network technologies, and asks how to make a level-2 bridge work within
it. My recommendation would be:
 1) not to do it. I think it is a big mistake to let level 2 technology
        cross administrative boundaries. Personally I prefer level 3
        technology everywhere, but there are good arguments on both sides.
        But I see nothing in favor of leve 2 technology connecting networks
        where different people are going to be responsible for diagnosing
        problems. Since this issue has come up so many times, I now have
        a canned response which I will mail to the original poster
        under separate cover (to avoid boring the rest of you). We believe
        that the next generation of gateways (based on 68020 processors
        instead of 68000), which should be available in December or January
        from at least cisco and Proteon, will have throughput close to that
        of a bridge. The primary performance limitation will then be
        on long back-to-back strings of packets. That will be resolved
        by new Ethernet controllers, which should also be available shortly.
        Even in the current generation, throughput with gateways is enough
        for most networks. From your description, I believe you would
        see no performance problems from using routers instead of
        bridges.
 2) if you must do it, I would set the subnet mask to 255.255.255.0
        on those machines were you can have multiple subnets on one
        interface. All BSD-based systems allow this, and I think
        many others as well. On a BSD system, you say
                route add x.y.z.0 youraddress 0
        for each subnet that you want to add as being local. For systems
        where this is not possible, I would set the subnet mask to
        255.255.0.0. If you have any such systems, then any actual level
        3 gateways that may be present in your configuration (Apollo?)
        will have to be able to do proxy ARP.



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