[lug] ARP problems with Linux...

celttechie (Brian Jarrett) celttechie at yahoo.com
Thu Feb 22 14:54:36 MST 2001

> That's odd.  What's your kernel version?  Show us your 'arp' output.  If
kernel is >= 2.2 make sure that 'cat /proc/sys/net/ipv4/conf/*/proxy_arp'
outputs all zeros.  If kernel < 2.2 make sure that you don't have a proxy
arp entry for the entire net.

I did the check for proxy_arp and it is all zeros.  (checked eth0, eth1 and

> Under normal circumstances, it seems to me that only the interface bound
to the IP address in question would respond.  It really sounds like proxy
arp is happening -- the fact that the second (proxy) response is delayed
makes sense based on the proxy_delay variable (defaults to 0.8 seconds).
see ARP(7).

I would think so as well, but it's simply not set.  The other thing about
this is that it worked fine for several months after initial install and has
only been giving these problems for the last few weeks.  (It's not
production, but I'm testing to see what issues are there -- like this one.)
In that time frame I started trying to get ssh running so I could configure
the firewall from anywhere.  I don't even think I could add a firewall rule
to keep responses from leaving the eth1 interface because ARPs (while part
of IP) are all in ethernet frames.


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