Re: Ethernet TCP/IP broadcasts: help


Tait Cyrus (hi!cyrus@hc.dspo.gov)
Fri, 3 Apr 87 21:18:26 MST


In article <In article <459@cernvax.UUCP> cernvax!jmg () writes:
>
>Last Wednesday (yes, it was April 1st; no it was NO JOKE) we got a
>situation on our Ethernet where a particular telnet RST packet from
>a host to a client was being sent inside a broadcast packet. The
>trouble was that this same broadcast packet was being sent out repeatedly
>by just about every TCP/IP host on our Ethernet (including both VMS
>with Wollongong and 4.2BSD). Thus, we were seeing about 1000 broadcast
>packets per second, coming from many diffferent sources but all containing
>this same RST information. This was, of course, killing all the small
>microvaxes and weaker 750/780 etc., with only the big 8800 having enough
>clout to continue apparently normally.
>
>We eventually stopped it by disconnecting all of the offenders, much
>to their disgust. After that everything started fine.
>
>Since we started installing Ethernet some years ago we have never seen
>such a catastrophic situation. Therefore, if anyone has any idea why
>so many vaxes should start rebroadcasting packets which were nothing
>to do with them I should be eternally grateful.
>
>Mike Gerard

 We had a simular problem with one of our micro vax II running Ultrix.
 There had been a brown out (power surge) and all our machines continued
 to run (more uvax II's and sun 2's and 3's). We noticed that the network
 was slow though. After some investigation we determined that this one
 uvax II was rebroadcasting every packet on the network 4, yes four times.
 We tried 'ifconfig down' and then 'ifconfig up' without any success.
 The only thing we could do was to reboot.

 A possible explanation was that the dequna's table of valid ethernet
 addresses to accept got hosed. If this occured then it would basically
 be like in promiscuous mode. On receiving these packets it would determine
 that none of the packets were for it so it would REbroadcast these packets.
 This still does not explain why it was duplicating packets.

 Strange............

 Sorry this is no help but, ....

--
    @__________@    W. Tait Cyrus   (505) 277-0806
   /|	      /|    University of New Mexico
  / |	     / |    Dept of EECE - Hypercube Project
 @__|_______@  |    Albuquerque, New Mexico 87131
 |  |	    |  |
 |  |  hc   |  |    e-mail:
 |  @.......|..@       cyrus@hc.dspo.gov or cyrus@hc.arpa or
 | /	    | /	       {gatech|ucbvax|convex}!unmvax!hi!cyrus
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