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Old 04-03-2016, 05:10 AM   #1
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Question strange ARP response

Hi guys,

I have a very strange problem. One of my linux machines inside my LAN thinks at has 2 IP's even though only one is configured. The network setup is simple. Just one adapter:

pi@backup:/etc/network $ cat interfaces
auto lo
iface lo inet loopback

auto eth0
allow-hotplug eth0
iface eth0 inet static
dns-domain huckmuc.lan

#auto eth1
#iface eth1 inet manual

pi@backup:/etc $ cat networks
pi@backup:/etc $ sudo arp -a
fileserver.huckmuc.lan ( at b8:27:eb:9f:68:24 [ether] on eth0
vigor.huckmuc.lan ( at 00:1d:aa:dd:1a:e0 [ether] on eth0
? ( at 8c:89:a5:0b:5c:27 [ether] on eth0
smarthome.huckmuc.lan ( at b8:27:eb:b0:60:91 [ether] on eth0
Looks simple as hell to me.

Now - for any strange reason - when I do an arp request in the same network, this machine also responds to which is not assigned:

Wireshark from my Windows Notebook:

"2","0.551391","Micro-St_0b:5c:27","Broadcast","ARP","42","Who has Tell"
"3","0.551665","Raspberr_f2:46:d5","Micro-St_0b:5c:27","ARP","60"," is at b8:27:eb:f2:46:d5"
It also answers to the configured IP address with the same MAC:
"6","1.140399","Micro-St_0b:5c:27","Broadcast","ARP","42","Who has Tell"
"7","1.140631","Raspberr_f2:46:d5","Micro-St_0b:5c:27","ARP","60"," is at b8:27:eb:f2:46:d5"
I have to mention that during the installation of this new machine it got an IP assigned via DHCP (which is possibly But now it is configured as static.

This is completely not understandable. Hope some network guru has a hint for me.
Old 04-04-2016, 05:58 AM   #2
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Have you tried
cd /etc
grep -r '192\.168\.0\.123' *
and see where you have that configured?
Old 04-04-2016, 11:23 AM   #3
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Also look at your routing table.

route -n
Might have a route listed in there.
Old 04-11-2016, 03:44 AM   #4
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I dont think arp has anything to do with assigning IPs. It is just used to discover devices on network.

If your system does get two ips then


on that particular machine should show it.

I have a wierd feeling about arp-poisoning here, ( hope im wrong)

Is that a Raspberry Pi device indicated there in your wireshark capture ?
Old 04-12-2016, 04:48 PM   #5
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Only two choices exist. Either it is on that Pi or from outside your lan. How is this topology? Disconnect the wan and see if it still exists. Better still use cable from Pi to only other system and see if it still exists.


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