Re: ICMP6 redirect

Andrew McGregor <> Wed, 25 July 2012 07:12 UTC

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Subject: Re: ICMP6 redirect
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From: Andrew McGregor <>
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Date: Wed, 25 Jul 2012 19:11:53 +1200
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To: Hesham Soliman <>
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On 24/07/2012, at 4:45 PM, Hesham Soliman wrote:

>>> => The router doesn't need to know the host's route table, it knows which
>>> address it included in its RAs, which is what the host records.
>>> I'm not sure why you think that there is no way the router can construct
>>> that message reliably. If it uses the same address it uses for its RAs,
>>> it
>>> can construct the message.
>> Ah.  Well, that will certainly help, but consider a situation where there
>> are no RAs, 
> => Where is that situation possible/deployed? It's hard to consider
> something that is against the spec you're commenting on :)

Sure, it is not a situation contemplated by the ND spec.  So, do you mean to say it is incorrect configuration for a router to have forwarding on and not be sending RAs, and therefore you should not send redirects if you are not sending RAs?  That works as a resolution for me, in terms of specs.

However, if it is not a misconfiguration, and you wish to redirect traffic that has a better first hop, or is on-link but the host for whatever reason does not know that, is that possible?  Should it be?

I suspect it is a common situation, no matter that it's completely broken.