arp problem? Howto fix

Craig White craigwhite at azapple.com
Fri Jul 23 04:10:56 UTC 2004


On Thu, 2004-07-22 at 19:34, Gene Heskett wrote:
> On Thursday 22 July 2004 22:13, Craig White wrote:
> [... long description]>
> >----
> >don't know if you've solved this and not entirely sure which FC we
> > are talking about but I would check for the wrong module being
> > assigned to the switched NIC in the following places...
> >/etc/modules.conf
> >/etc/modprobe.conf
> >/etc/sysconfig/network-scripts/ifcfg-ethX
> >
> >I would remove the 'old' module ... rmmod rtl8139too or whatever it
> > was and insmod the new module if known or simply run kudzu and then
> > restart network service.
> >
> >Craig
> 
> No, I haven't solved it, yet, and the system is FC1, with a 2.6.8-rc2 
> kernel.
> 
> What I did about an hour ago was to shutdown and re-insert the 8139too 
> card, reboot, use redhat-config-network utility to destroy the old 
> eth0 that was using the forcedeth module, then rebuilt eth0 using the 
> 8139too driver.  I had it all up and running great about 10 minutes 
> from powerup.
> 
> So the only thing thats changed is the port the cat5 cable to the 
> switch is plugged into on the back of the machine, plus the driver 
> and "card" to use.  All else is identical EXCEPT for the MAC address 
> for the forcedeth version ANAICT.  FWIW, the 8139too driver is still 
> built into the kernel, whereas forcedeth has to be loaded.  But that 
> didn't seem to make any noticeable difference that I could see or 
> feel.  Ping times to the firewall box were faster on forcedeth, < .1 
> millisecond.  Usually its around .2 milliseconds.
> 
> I'm slowly going bald (its all grey and getting pretty thin on top 
> anyway :) from fooling with this.  I may record the MAC from this 
> card, go into the bios and set that one to the same just for grins 
> yet.  Another day though, this ones gotten long in the tooth.
----
In all the years I have fooled with networking, I have only had to
change a MAC twice and both times involved stupid, old software.

I would check the routing tables - perhaps your default route isn't what
it's supposed to be - or - as I was suggesting before, another module
was loading in place of the correct module.

Steve Cowles concept of flushing iptables, clearing the arp cache on
machine you are calling 'router' seem to be good ones and I wold suppose
a few seconds of tcpdump will let you know whether packets are getting
to 'router'

Craig





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