[Techtalk] arp

Jeff Dike jdike at karaya.com
Mon Oct 29 22:05:05 EST 2001

rolick571 at duq.edu said:
> arp -v -i eth0 -s 0:0:0:0:0:1 pub
> where 0:0:0:0:0:1 is the mac address of the router.

I normally use something like
	arp -Ds eth0 pub

> then in the arp cache, is the following:
> ? ( at * PERM PUP on eth0 

And my arp cache ends up looking like

? ( at * PERM PUP on eth0

Which looks similar to your, with the exception that my proxy arps work :-)

One thing that other people have found necessary is to
	echo 1 > /proc/sys/net/ipv4/conf/DEVICE/proxy_arp

I've never figured out what that does, but it seems to fix some networking
problems.  (The background to this is that I use proxy arp to connect UML
virtual machines to the rest of the net.  They communicate with the host
over a TUN/TAP or ethertap device, which acts as a single strand of ethernet,
making the local network split across two ethernets with the host as the
router in between.  One of my users figured out that fiddling 
/proc/.../proxy_arp fixed some connectivity problems, so I made it standard.)


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