Link level Ethernet bridges (Modified)! does that mean joke?

C. Philip Wood (cpw%sneezy@LANL.GOV)
Tue, 23 Feb 88 16:12:20 MST

Naming names. No dispersions intended. But, hey, I want to know!

Does anyone on this list have an inkling about why given the following
configuration that 99.9% packets destined for an HP system are not passed
through a DEC MacLevel Bridge? (Thats right, one maybe every 300 to 400

        segment #1 segment #2

  8:0:20:1:33:1e Ha--| |--Hz 8:0:2b:3:92:23
                      | |
  8:0:20:1:47:d2 Hb--| |--Hz-1 8:0:20:1:d7:e5
                      |icmp icmp |--Hy 2:7:1:0:a6:59
   8:0:9:0:65:3d Hp*--|echo-> echo->|--Hx aa:0:4:0:da:4 hummmm.
                       nada <-reply |
                      . .
                      . .
                      . .
  8:0:20:1:66:6a Hq--| |--Hr 8:0:2b:3:91:5c
                      |----?[DEC lanBridge]?---|

        SUBNET 1 of Class B network 128.165, mask==0xfffffc00

There is probably alot of irreverent/irrelevant, but, it was fun.

All the hosts Ha through Hz with the exception of Hp can communicate over
the ether. By communicate, I mean ICMP echo, vanilla, no ip options.
All the hosts Ha through Hq ***INCLUDING*** Hp* CAN communicate
over segment #1. When attempting an ICMP Echo between Hp and Hx, an
'etherfind' on segment #2 shows an echo and echo reply
reply packet. While an 'etherfind' on segment #1 shows an echo packet,
one out of 400 reply's make it. Do this with any other pair, like
Ha -- Hx, or Hp -- Ha, and it works bwainoh.

* Hp == HP-UX hp320 6.01 B 9000/320 Is there something strange about that
        address? ... I don't think so.
        (Little is known about this one of a kind on our net. It would be
         nice if we could look at its "arp" tables, but they did it their
         way, what if? ..., Rumor has it that the system is BSD3.4 made
         to look like system V.)
  Ha == Sun UNIX 4.2 Release 3.4
        (This release is known to be worthless on a subnet, however, it
         appears to work if it stands alone and does not use the yellow
  Hr == VAX-11/785 running VMS/Wollengon (3.1) (They do ICMP mask request
        replys correctly, its about time!, but don't send them too many
        packets in a row!)
  Hz == VAX-11/785 running BSD 4.3 (They forget to swap their subnetmask
        and mess up anyone foolish enough to broadcast an ICMP mask request,
        fixed by me, cause I got source!)
Hz-1 == Sun 3/260 running 3.5 (Hey, I can ifconfig netmasks and broadcast
        addresses, but darn I still can't ip route between 128.165.4.xx
        (mask == 0xfffffc00) and (mask == 0xffffffe0), and
        double darn the routed just chewed up all my cpu and flooded
        the net with gosh knows what kind of "routing" packets, and those
        yellow lights on the DEC LanBridge just don't blink anymore, their
  Hx == VAX-8600 running Ultrix V2.0-1 (Talk about skizoid, this dude
        talks DECNET and INTERNET of'n a one DEUNA and it's network
        application suite has been loaded at j random times with:

                gethostbyname from /etc/hosts
                gethostbyname from /etc/yp
                gethostbyname from /etc/resolv.conf (yup, ypserv -i)

        So try, and answer a vanilla users question like "why can I rsh
        and not rlogin!")
  Hy == Celerity running Accel UNIX, (They were nice to rush us a patch
        for their systems that fixed a bug that stomped on SUN clients
        attempting to boot.
... == Bridge, Inc. terminal servers, Bridge, Inc. GS7's and GS3's, pure
        DECNET VMS VAX systems, IBMPC's, KINETICS MacInTosh "gateway's",
        miscelaneous DEC terminal servers, IBM RT's which respond to
        ICMP echo requests and return the IP Record Route option, bless
        there heart!)

Phil Wood

P.S. I'm not afraid anymore. I think I'll save this one.


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