Sending ARP request to unicast MAC instead of broadcast MAC address?

Steven King sking at kingrst.com
Thu Jun 17 21:14:45 CDT 2010


I believe they call this a Gratuitous ARP Request. It is used
automatically when interfaces are brought up to detect IP conflicts.

On 6/17/10 5:45 PM, Chris Woodfield wrote:
> Looks like all the replies I got were private, so thanks all - to summarize, I got everything from "Read The Fine Kernel Source" to "Read The Fine RFC" to "Read RFC 1122, Section 2.3.2.1, it's quite a Fine read". 
>
> So for other folks out there like me who obviously can't read RFCs, the answer is "yes". :)
>
> -C
>
> On Jun 16, 2010, at 3:57 51PM, Chris Woodfield wrote:
>
>   
>> OK, this sounds Really Wacky (or, Really Hacky if you're into puns) but there's a reason for it, I swear...
>>
>> Will typical OSS UNIX kernels (Linux, BSD, MacOS X, etc) reply to a crafted ARP request that, instead of having FF:FF:FF:FF:FF:FF as its destination MAC address, is instead sent to the already-known unicast MAC address of the host? 
>>
>> Next, what would be your utility of choice for crafting such a packet? Or is this something one would need to code up by hand in a lower-level language?
>>
>> Thanks,
>>
>> -C
>>     
>
>   

-- 
Steve King

Senior Linux Engineer - Advance Internet, Inc.
Cisco Certified Network Associate
CompTIA Linux+ Certified Professional
CompTIA A+ Certified Professional





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