Re: [webmin-l] Off-Topic arpwatch & Flip Flopping NICs

[Neal M. <Ne...@mo...>]

I was just looking at something similar.  From the Intel driver readme:




Multiple Interfaces on Same Ethernet Broadcast Network
------------------------------------------------------
Due to the default ARP behavior on Linux, it is not possible to have one
system on two IP networks in the same Ethernet broadcast domain
(non-partitioned switch) behave as expected. All Ethernet interfaces
will respond to IP traffic for any IP address assigned to the system.
This results in unbalanced receive traffic.

If you have multiple interfaces in a server, either turn on ARP
filtering by entering:

echo 1 > /proc/sys/net/ipv4/conf/all/arp_filter
(this only works if your kernel's version is higher than 2.4.5),

NOTE: This setting is not saved across reboots. The configuration change
can be made permanent by adding the line:
net.ipv4.conf.all.arp_filter =3D 1
to the file /etc/sysctl.conf

or,

install the interfaces in separate broadcast domains (either in
different switches or in a switch partitioned to VLANs).





-----Original Message-----
From: web...@li...
[mailto:web...@li...] On Behalf Of Cary
Robinson
Sent: Thursday, June 22, 2006 9:09 AM
To: web...@li...
Subject: [webmin-l] Off-Topic arpwatch & Flip Flopping NICs

Sorry to trouble this list, but I have looked for days trying to find=20
info on my Flip Flopping NICs.

I have 2 NICs, eth0 & eth1 and have assigned them the IP addresses=20
192.168.1.11 & 192.168.1.12 respectively. arpwatch reports that the=20
IP address 192.168.1.12 hops back & forth between the 2 NICs.

Can anybody point me to a URL or book that can educate me on this=20
"Flip Flop" thing ?


Here are a few of the reports that arpwatch sends me via email.

             hostname: <unknown>
           ip address: 192.168.1.12
     ethernet address: 0:c0:9f:b:96:ec
      ethernet vendor: QUANTA COMPUTER, INC.
old ethernet address: 0:f:b5:fb:26:a9
  old ethernet vendor: <unknown>
            timestamp: Wednesday, June 21, 2006 11:28:53 -0500
   previous timestamp: Wednesday, June 21, 2006 11:28:53 -0500
                delta: 0 seconds



             hostname: <unknown>
           ip address: 192.168.1.12
     ethernet address: 0:f:b5:fb:26:a9
      ethernet vendor: <unknown>
old ethernet address: 0:c0:9f:b:96:ec
  old ethernet vendor: QUANTA COMPUTER, INC.
            timestamp: Wednesday, June 21, 2006 11:29:00 -0500
   previous timestamp: Wednesday, June 21, 2006 11:29:00 -0500
                delta: 0 seconds




             hostname: <unknown>
           ip address: 192.168.1.12
     ethernet address: 0:c0:9f:b:96:ec
      ethernet vendor: QUANTA COMPUTER, INC.
old ethernet address: 0:f:b5:fb:26:a9
  old ethernet vendor: <unknown>
            timestamp: Wednesday, June 21, 2006 11:29:01 -0500
   previous timestamp: Wednesday, June 21, 2006 11:29:00 -0500
                delta: 1 second


Thanks,
Cary Robinson

 =20


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