Sorry, found out, that there is a specific ML list for this .. posted this to LKML too. (but I have some updates about this) Maybe it is a setting, i have searched everywhere, but this is really mysterious take a linux, configure this kind eth0: 192.168.10.200 / 255.255.255.0 eth1: 192.168.10.201 / 255.255.255.0 Both Interfaces are "real ethernet cards" and are connected to same switch if you take now a 3'rd machine, and do a arping -c 1 192.168.10.200 >60 bytes from 00:0c:29:bc:96:fe ( 192.168.10.200): index=0 time=645.876 usec >60 bytes from 00:0c:29:bc:96:f4 ( 192.168.10.200): index=1 time=1.472 msec arping -c 1 192.168.10.201 >60 bytes from 00:0c:29:bc:96:fe (192.168.10.201 ): index=0 time=833.988 usec >60 bytes from 00:0c:29:bc:96:f4 (192.168.10.201): index=1 time=1.211 msec in fact, this is "fuck" as arp table of switches and other machines are not knowing what to do compared to Windows2000, Windows just gives you "one" entry back, (and YES: the real too...) This "bug" is in 2.4.x ( i tested may of them) and 2.6.x (not tested all, but it is exisintg in ubuntu with 2.6.15) , not sure about 2.x from my reading of RFC, this is "not legal" and even made it possible, that my switch killed the server, because as he thought, i am spoofing him. It gets much more funny, when you have 3 network cards running :-) then you get 3 replys :-) # arping -c 1 192.168.10.200 ARPING 192.168.10.200 60 bytes from 00:0c:29:bc:96:08 (192.168.10.200 ): index=0 time=499.010 usec 60 bytes from 00:0c:29:bc:96:fe (192.168.10.200): index=1 time=878.096 usec 60 bytes from 00:0c:29:bc:96:f4 ( 192.168.10.200 ): index=2 time=1.163 msec --- 192.168.10.200 statistics --- 1 packets transmitted, 3 packets received, -200% unanswered ..... btw: control, if you have spoofing filter active if you have a spoofing filter active, like in debian, kill ist echo 0 > /proc/sys/net/ipv4/conf/all/rp_filter the system answers on both IP (or 3 ipadresse) always with the same mac address with filter disabled, the above phaenomn will come again. Yes, i think this is a bug. Personally, i think, it is a bug in the IP stack, as "all interfaces" receive the Broadcast, and then, arp_send(ARPOP_REPLY,ETH_P_ARP,sip,dev,tip,sha,dev->dev_addr,sha); answers but it answers the request on all interfaces, with the "MAC" of the interface, which comes from dev->dev_addr Update: If you configure eth0: 192.168.10.200 / 255.255.255.0 eth1: 192.168.10.201 / 255.255.255.0 eth2: 1.2.3.4 / 255.255.255.0 (have added 3 network cards to the system) You also get 3 ARP reply's regards Lehner Franz - To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
