Linux, in the 2.4 kernels, has this default behaviour. The ARP reply for an IP goes from any interface on the system, not just the one on which the IP is configured.
You can change this behaviour by setting:
/proc/sys/net/ipv4/conf/all/arp_filter = 1
Or, if you want to control this for just one interface:
/proc/sys/net/ipv4/conf/interface name e.g. eth0/arp_filter = 1
As an aside, I would also recommed setting up different VLANs, if your switch support them. That way you can get different "logical" switches.
Regards, -Varun
Marco Berizzi wrote:
Hello everybody.
I have a problem with my firewall rules on my Slackware Linux box 9.0 (kernel 2.4.20-xfs). This system is configured with 3 NIC (one for the router, one for the dmz, and the other for the private net). I have written a firewall (iptables) that is processing packet based also on the incoming interface. This firewall is connected in a not good environment where all the NIC (and the router) are connected to the same switch (don't ask me why). Here is the problem: an incoming packet from the private net sometimes is catched by the priv NIC, sometimes is catched by the DMZ nic and sometimes is catched by router NIC. This happens (I think) because when a client (windoze) sends an arp request with the priv NIC IP, linux replies with the MAC address from any of the 3 NIC and not only with the MAC from the priv NIC.
Is there any setting in /proc to prevent this? shared_media perhaps?
TIA
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