[Dnsmasq-discuss] Difference between SLAAC and RA-ONLY mode

Simon Kelley simon at thekelleys.org.uk
Thu Dec 19 15:48:44 GMT 2013


On 18/12/13 15:21, Shixiong Shang wrote:
> Hi, Simon:
> 
> This is very helpful! Thanks a lot for your confirmation!
> 
> A quick question, is there any way we can set M-bit to 1 and set
> A-bit to 0? In other words, I am trying to force VM to use DHCPv6
> only, but not SLAAC?

Yes, configure the dhcp-range _only_ for DHCPv6 ie


dhcp-range=<prefix>::1,<prefix>::200

and set the --enable-ra flag

That will do RA just to support the DHCPv6, ie MO bits set, A bit clear.


Cheers,

Simon.

> 
> Thanks again!
> 
> Shixiong
> 
> 
> 
> 
> 
> 
>> On Dec 17, 2013, at 1:08 PM, Simon Kelley<simon at thekelleys.org.uk>
>> wrote:
>> 
>>> On 17/12/13 17:34, Shixiong Shang wrote: Hi, Simon:
>>> 
>>> Thanks a lot for your quick clarification! Just want to make sure
>>> I clearly understand what you mean….if the dhcp-range contains a
>>> range of IPv6 address, then slaac should enable dhcpv6 + ra; if
>>> the dhcp-range contains the single IPv6 address, then slack will
>>> only do ra, but not dhcpv6…..Same as ra-only. In other words,
>>> how slaac/ra-only set MOAL bits depends on dhcp-range…..Is my 
>>> understanding correct?
>> 
>> That's correct.
>> 
>> 
>> Simon.
>> 
>>> 
>>> Shixiong
>>> 
>>> 
>>> 
>>> On Dec 17, 2013, at 11:55 AM, Simon
>>> Kelley<simon at thekelleys.org.uk> wrote:
>>> 
>>>>> On 17/12/13 12:29, Shixiong Shang wrote: Hi, guys:
>>>>> 
>>>>> I tried both “slaac” mode and “ra-only” modes with dnsmasq 
>>>>> version 2.66. One thing I noticed was, both modes set the
>>>>> same bit value in the RA:
>>>>> 
>>>>> M-bit = 0, O-bit = 0, A-bit = 1, L-bit = 1.
>>>>> 
>>>>> I am wondering what’s the difference between these two modes 
>>>>> then? Would you please shed some light on it?
>>>> 
>>>> There's no difference: "slaac" and "ra-only" have exactly the
>>>> same effect. Reading back the manpage, the description is very
>>>> confusing and should be re-written.
>>>> 
>>>> The reason for having two different keywords is that they can
>>>> be used with and without DHCP
>>>> 
>>>> dhcp-range = 1234::1, 1234::100, slaac
>>>> 
>>>> will do RA with MOAL bits all set, and provide DHCPv6
>>>> 
>>>> dhcp-range = 1234::1, slaac
>>>> 
>>>> will do RA with only AL bits set, and not DHCP. It's maybe
>>>> clearer to be able to be able to write.
>>>> 
>>>> dhcp-range = 1234::1, ra-only
>>>> 
>>>> in this case.
>>>> 
>>>> Cheers,
>>>> 
>>>> Simon.
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> 
>>>>> Thanks!
>>>>> 
>>>>> Shixiong _______________________________________________ 
>>>>> Dnsmasq-discuss mailing list 
>>>>> Dnsmasq-discuss at lists.thekelleys.org.uk 
>>>>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>>>>
>>>>
>>>>
>>>>> 
_______________________________________________ Dnsmasq-discuss
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>>
>



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