[Dnsmasq-discuss] Sending RA without dhcp-range

[Shixiong Shang]

Hi, Simon:

Truly appreciate your further clarification!

The use case I am dealing with now is, there is another DHCPv6 server (stateful or stateless) on the same link. Dnsmasq only needs to send RA to trigger DHCPv6 Solicit in the same way router does. 

Being said, is it possible that we can shutdown the DHCPv6 port, so dnsmasq won’t listen to DHCPv6 message? Or change it from different port?

Thanks again!

Shixiong




On Jan 17, 2014, at 9:32 AM, Simon Kelley <simon at thekelleys.org.uk> wrote:

> On 17/01/14 14:21, Shixiong Shang wrote:
>> Hi, Simon and Albert:
>> 
>> Thank both of you for quick response!
>> 
>> According to the man page online, the mode like “ra-only”, and
>> “ra-stateless” are only used as part of “dhcp-range” option. However,
>> this will also turn dnsmasq to DHCPv6 server, which I try to avoid.
> 
> It confusing, I agree but
> 
> dhcp-range=<1234:5678::,ra-only
> 
> _doesn't turn on the DHCPv6 server, and least for that prefix, and
> 
> dhcp-range=<1234:5678::,ra-stateless
> 
> turns on the DHCPv6 server only to replt to information-requests, not address allocation.
> 
> 
> Cheers,
> 
> Simon.
> 
> 
> 
>> Would you please help me clarify how I can send RA on specific
>> interfaces with the right flags? The only thing I can think of is
>> leveraging “—ra-param”, but it doesn’t have place to put in mode
>> keywords…..
>> 
>> Thanks again!
>> 
>> Shixiong
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Jan 17, 2014, at 5:49 AM, Simon Kelley <simon at thekelleys.org.uk>
>> wrote:
>> 
>>> On 17/01/14 06:10, Albert ARIBAUD wrote:
>>>> Le 17/01/2014 05:30, Shixiong Shang a écrit :
>>>>> Hi, experts:
>>>>> 
>>>>> Is it possible that dnsmasq can send out RA with either A=0,
>>>>> MO=1 (i.e. for DHCPv6 Stateful), or AO=1, M=0 (i.e. for DHCPv6
>>>>> Stateless) WITHOUT dhcp-range? What I am trying to achieve here
>>>>> is using dnsmasq to send out RA to trigger DHCPv6 Stateful or
>>>>> DHCPv6 Stateless mode without acting as DHCPv6 server. Based on
>>>>> my reading, I am under the impression that “—enable-ra” must be
>>>>> used with “—dhcp-range”. Otherwise, dnsmasq will not send
>>>>> RA…..
>>>> 
>>>> You are right about having to add enable-ra.
>>>> 
>>>> However there is a syntax of dhcp-range which will not cause
>>>> DHCPv6.
>>>> 
>>>> As per 'man dnsmasq' (search for 'dhcp-range'), the possible
>>>> modes for IPv6 ranges include 'ra-only', which will previsely
>>>> enable RAs without enabling any DHCP.
>>>> 
>>> 
>>> Neither of you are completely right.
>>> 
>>> enable-ra causes RA with A=0 and M = 1  O = 1 on every interface
>>> that's doing DHCP, just to instruct the clients to do stateful
>>> DHCP. It's intended as a simple option for systems which don't use
>>> RA at all.
>>> 
>>> You don't need to set enable-ra at all to do RA on specific
>>> interfaces with other flag combinations, ie
>>> 
>>> ra-only A=1 M=0 O=0 slaac   A=1 M=1 O=1 ra-stateless A=1 M=0 O=1
>>> 
>>> Cheers,
>>> 
>>> Simon.
>>> 
>> 
>