arp: unknown hardware address

[Louis Mamakos]

The Address Resolution Protocol (ARP) contains an address format  
identifiers as part of the frame format.  This is so it could be used  
as generalized solution to discover different types of addresses on a  
broadcast network.  For IP, the address format in the frame ought to  
be (as I recall) 0x0800 to denote an IPv4 protocol addresses and  
0x0001 to denote Ethernet hardware addresses.  It seems like some  
other host on your network has likely emitted malformed ARP messages.

UTSL: /usr/src/sys/netinet/if_ether.c:arpintr()

louie

On Feb 22, 2008, at 5:09 AM, sebosik at demax.sk wrote:

> Hi
>
> I`ve got the same messages on FreeBSD 6-STABLE (tracked every second
> week). I think that somebody is using default MAC address on network.
>
> Best regards
>
>> Hi!
>>
>> This morning, I found this in the daily periodic mail from a RELENG_7
>> machine:
>>
>> +arp: unknown hardware address format (0x0000)
>> +arp: unknown hardware address format (0x0000)
>> +arp: unknown hardware address format (0x0000)
>> +arp: unknown hardware address format (0x0000)
>> +arp: unknown hardware address format (0x0000)
>>
>> I checked my yesterdays' logs and found:
>>
>> Feb 21 20:56:39 bellona dhcpd: DHCPREQUEST for 192.168.178.20 from
>> 00:18:de:a4:b
>> 8:6a via aue0: wrong network.
>> Feb 21 20:56:39 bellona dhcpd: DHCPNAK on 192.168.178.20 to
>> 00:18:de:a4:b8:6a vi
>> a aue0
>> Feb 21 20:56:40 bellona kernel: arp: unknown hardware address format
>> (0x0000)
>> Feb 21 20:56:40 bellona kernel: Feb 21 20:56:40 bellona kernel: arp:
>> unknown hardware address format (0x0000)
>> Feb 21 20:56:42 bellona kernel: arp: unknown hardware address format
>> (0x0000)
>> Feb 21 20:56:47 bellona last message repeated 3 times
>> Feb 21 20:56:51 bellona dhcpd: DHCPDISCOVER from 00:18:de:a4:b8:6a  
>> via
>> aue0
>> Feb 21 20:56:51 bellona kernel: Feb 21 20:56:51 bellona dhcpd:
>> icmp_echorequest 192.168.20.249: Operation not permitted
>> Feb 21 20:56:52 bellona dhcpd: DHCPOFFER on 192.168.20.249 to
>> 00:18:de:a4:b8:6a (lp4) via aue0
>>
>>
>> 7.0-PRERELEASE FreeBSD 7.0-PRERELEASE #8: Sun Feb 17 19:13:08 CET  
>> 2008
>>
>> The network the dhcp client was requesting (192.168.178.20) is not  
>> mine,
>> dhcpd rejected that address and offered another one. But why does
>> FreeBSD complain about the bad hardware address?
>>
>> Any explanations?
>>
>> Volker
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>>
>
>
> ---
> Jan Sebosik
> sebosik at demax.sk
>
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>