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From: "Martin Petraschek" <petraschek@ftw.at>
To: "Lowell Gilbert" <freebsd-questions-local@be-well.ilk.org>
Date: Thu, 07 Apr 2005 16:20:24 +0200
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cc: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org>
Subject: Re: IPv6 ICMP multicast response
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On 07 Apr 2005 09:30:29 -0400, Lowell Gilbert wrote:

>"Martin Petraschek" <petraschek@ftw.at> writes:
>
>> By default, FreeBSD does not reply to ICMP multicast echo 
>>requests. For IPv4 this behaviour  can be changed with
>> 
>> sysctl  net.inet.icmp.bmcastecho=0|1
>> 
>> Is there a similar control for IPv6?
>
>No.  That would violate RFC 2463, section 2.4(e.2).
>As well as being a bad idea.

The section you are referencing in RFC 2463 is concerning ICMP 
ERROR messages. Echo requests/responses are informational 
messages, therefore this section does not apply.

The same RFC 2463, section 4.2 states:

   An Echo Reply SHOULD be sent in response to an Echo 
   Request message sent to an IPv6 multicast address.  The 
   source address of the reply MUST be a unicast address 
   belonging to the interface on which the multicast Echo Request 
   message was received.

Therefore, the OS _should_ respond to a multicast echo request!

Martin