[lug] Linux boxes drop off the net? Router problem?

[Gary Frerking (TurboPower)]

>> Anyway, in 'normal' circumstances ARP isn't 'routed', after all, this is
the protocol used to detect _hardware_ adresses. <<

Yes, that was my understanding of ARP too.

>> arp. 'arp -anv' will show you the content of the arp cache. <<

I tried that on two of my Linux boxes -- each one had a couple entries
(these machines don't interact with machines on the local network very
often). Anyway, there *were* entires at least. I pinged one of the machines
from another machine, and the "pinger" was added to the cache as expected.
For kicks, I checked the ARP cache on a Solaris box connected to the same
hub as the two Linux boxes I checked -- the Solaris box had *many* entries
(including entires for each of the Linux boxes; seemingly proving that they
indeed respond to ARP requests, and that they indeed have different hardware
addresses).

>> BTW, is it possible that some of your boxes are misconfigured? <<

Ohhh, it's always possible -- it's obvious that *something* is
misconfigured. We've checked the Linux boxes (5 of them) over pretty
carefully though. The 5 boxes were set up independently by three different
people that all are fairly good with Linux. Is it possible we all made the
same mistake? I guess so, but the odds seem a bit slim.

>> Is there anyway that you can isolate a ping so that it does NOT hit the
router? <<

Nothing immediately comes to mind, but I'll see if I can come up with
something. I mentioned earlier that we tried the opposite (connected one of
the Linux boxes directly into the router) and it showed the same symptoms --
wouldn't that effectively eliminate the switch as being the problem?

>> I also believe that both the switch and the Cisco router have the ability
to log into and display current ARP tables. <<

Probably so -- I'll see if I can get the SysAdmin to do that for me.

>> Unfortunately this is where my knowledge of routing ends. <<

I reached my limit some time ago. <g>

I just installed ntop on one of the machines, I'll let that cook awhile and
see if it yields any further clues.

-- Gary