[Gllug] Weird networking problem with 2.6 kernel

[John Winters]

On Sun, 2004-06-20 at 12:35, Bruce Richardson wrote:
> On Sat, Jun 19, 2004 at 11:58:39AM +0100, john wrote:
> > 11:49:13.893114 00:50:8b:91:04:57 > ff:ff:ff:ff:ff:ff, ethertype ARP
> > (0x0806), length 60: arp who-has 192.168.100.16 tell 192.168.101.251
> 
> What is your subnet mask, there?  If it's the standard /24 mask then
> those boxes are on different subnets and would not ordinarily be
> generating ARP requests for each other.  If they are on separate
> subnets, which one were you running tcpdump on?

No, the netmask is /23 (odd I know).

I initially thought that it was just a case of another machine with the
same IP address, but I had the IP address for my box changed at the DHCP
server and I get the same result.  As soon as my box sends its ARP
request, something else on the network seems to pick it up and
re-broadcast it at 1 second intervals, faking my box's MAC address in it
as well.  I just can't imagine what kind of piece of kit would do that.

Actually - perhaps you've hit on something there.  If some sort of
router or bridge is configured wrongly (so that it thinks these two
boxes *are* on separate subnets) then it might be trying to do proxy ARP
requests.  I'm not sure I can explain all the symptoms though.

John

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