fxp(4) not responding to arp requests (aliases)
fox at verio.net
Mon Jul 2 16:47:28 UTC 2007
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Eduardo Meyer <dudu.meyer at gmail.com> wrote:
> When a host who is talking to be deletes its arp entry which has my IP
> address, communication goes down, and fxp2 never replies to arp
> requests. Completly ignores arp, in fact.
Your premise is that the fxp does not respond to arp request, but your
example does not show an arp request is being received.
> On host2:
> # arp -d 200.X.Y.5
I presume that host2 has IP 200.X.Y.6 and host1 has IP 200.X.Y.5, since
you didn't say.
> On host1:
> # tcpdump -n -v -i fxp2 arp
> tcpdump: listening on fxp2, link-type EN10MB (Ethernet), capture size 96 bytes
> And nothing happens.
Is host2 trying to send us traffic? You did not say.
Presumably if host2 is trying to send traffic to host1, you should see this:
12:41:43.932590 arp who-has 200.X.Y.5 tell 200.X.Y.6
12:41:44.932590 arp who-has 200.X.Y.5 tell 200.X.Y.6
12:41:45.932590 arp who-has 200.X.Y.5 tell 200.X.Y.6
In other words you should see a repeated arp request with no reply. Are
you suggesting that the interface is simply not receiving broadcasts?
> On host1 I cycle fxp2 up/down:
> # ifconfig fxp2 down && ifconfig fxp2 up
> And on host1 immediately I see:
> 12:41:08.860484 arp who-has 200.X.Y.6 tell 200.X.Y.5
> 12:41:08.862898 arp reply 200.X.Y.6 is-at 00:11:d8:52:04:fb
This doesn't look like host1 is suddenly receiving and replying to an
arp request. Instead, it is suddenly sending out an arp request for
another host. Why would it do that? I thought host1 was trying to
receive some traffic, not send.
> And on host2 immediately I see
> 12:41:42.932590 arp who-has 200.X.Y.5 tell 200.X.Y.7
> 12:41:57.515735 arp reply 200.X.Y.5 is-at 00:50:8b:be:64:a4
This is not even the same arp request/reply, so I am not sure what you
are pointing out here. Was host2 supposed to be asking for host1's ARP
all this time but it never got around to asking until just now? That
seems to imply a problem with host2, instead of host1. Also where did
this 200.X.Y.7 IP come from? I thought there were only two hosts here.
Maybe you could present a more complete description of which host is
attempting to send where, and what both hosts see, at the exact same
David DeSimone == Network Admin == fox at verio.net
"It took me fifteen years to discover that I had no
talent for writing, but I couldn't give it up because
by that time I was too famous. -- Robert Benchley
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