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<== Date ==> <== Thread ==>

Subject: Re: network problem w/ ioc
From: "Dale L. Brewe" <brewe@pnc.aps.anl.gov>
To: Chip Watson <Chip.Watson@jlab.org>
Cc: tech-talk@aps.anl.gov
Date: Wed, 25 Aug 1999 10:56:03 -0500
Chip
Well, something along these lines seems plausible, I guess, altho the gateway has not changed, nor have the ioc parameters. However, these problems surfaced a few days after a new main switch/router was installed. Clearly the problem seems to be at a pretty basic level, as I have troubles pinging the ioc with no CA clients running. I haven't found anything that looks bad in either hardware or software. In the ioc startup, I have routeAdd "0", "x.x.x.x" for our subnet gateway. Is this correct? It worked before, but could the routers be acting differently for some reason?
Dale
At 08:08 AM 8/25/99 , Chip Watson wrote:
Dale,

Your problem is similar to one I tracked down at PSI. If you
have a gateway (default routing node) improperly set in the
boot parameters of the IOC, then the following scenario can
happen:

(1) the first client connects, but the ioc sends all traffic for
that client through the gateway

(2) the gateway eventually sends a message to the ioc telling it
what the correct ethernet address for that host is (it doesn't want
to carry traffic unnecessarily)

(3) the ioc mistakenly updates the gateway address instead of
installing an explicit host entry

(4) the second client connects, and the ioc attempts to route
all traffic through the gateway again, but now it uses the
"updated" address for the gateway, which is client one

(5) client one refuses to forward the packets (lazy, huh?), so
the ioc appears to drop off the net for everyone except the
first client to have connected

Log into the ioc via the console if you can, and you can watch
this scenario play out.  Then, check your boot parameters and
either fix or remove the gateway entry.

Chip


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Dale L. Brewe PNC-CAT/U. of Washington ph: 630 252 0582 fax: 630 252 0580 Mail: Argonne National Laboratory/APS Bldg 435E sector 20 9700 S. Cass Ave. Argonne, IL 60439 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Replies:
Re: network problem w/ ioc Maren Purves
References:
network problem w/ ioc Dale L. Brewe
Re: network problem w/ ioc Chip Watson

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