Trying to get tcpdump to work

[Bill Roth]

In article <tih.673686101 at barsoom> tih at barsoom.nhh.no (Tom Ivar Helbekkmo) writes:
>I set up my packet filter to run in promiscuous mode here yesterday, on
>a 5000/200 with 4.1, and our whole VAXcluster (VMS) started crashing like
>nobody's business...  I've heard that promiscuous mode will break LAT if
>you've got LAT installed on the Ultrix host running it, which I haven't,
>but I'm wondering if it still may have been my experimenting that killed
>the VAXen.  We use LAT very extensively, in fact 3 out of every 4 packets
>on our ethernet are LAT packets.  Anybody know anything about it?
>
>-tih
>--
>Tom Ivar Helbekkmo, NHH, Bergen, Norway.  Telephone: +47-5-959205
>Postmaster for domain nhh.no.  Internet mail:  tih at barsoom.nhh.no


We (PSL) saw trhe same thing about 2 months ago. I started up tcpdump and left
for the weekend, only to find, on returning monday, that the entire net had been down
all weekend. The immediate fix was to pull the cable out of my DECStation.

I posted a question about it at the time, and received no answer. Perhaps this time
someone will respond.

>From the Wild Guess Department: I bet that LAT is implemented as a Read Write packetfliter
whereas the packetfilter mechanism is read only. Either that or enabling tcpdump stomps
all over the pf mechanism used to read and respond to LAT packets.

-- 

------------------------------------------------------------------------
Bill Roth,  University of Wisconsin Physical Sciences Laboratory
email: bill at pslu1.psl.wisc.edu bill at wiscpsl.bitnet   /  (608)-873-6651