Harping on ARP [LWN.net]

Harping on ARP

Posted Aug 22, 2003 0:33 UTC (Fri) by tmattox (subscriber, #4169)
In reply to: Harping on ARP by gswoods
Parent article: Harping on ARP

Yes it is related. The issue seems to be that Linux 2.4.x (and probabbly previous versions) selects the Source IP address used in its own ARP Request packets in a "different" way, but possibly still RFC compliant way. The result is that an ARP Request from a Linux box can have a Source IP address field that some devices and OS's consider to be invalid, and thus don't respond to the ARP Request. Again, it is unclear to me if Linux is really in the wrong on this, but it looks like at least two people are working on a patch to add a sysctl that would allow you to force the Source IP address in a Linux ARP Request packet to be set to an IP address of the outgoing NIC.
For now the best workaround seem to be to set a prefered source IP address for each route, using the "ip route ... src ..." command, and to echo "1" into the arp_filter sysctl in /proc for each NIC. I've not tested this myself, I just finished reading the LONG discussion on the linux-netdev mailing list.

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