Re: [Dnsmasq-discuss] Valid and Preferred lifetimes are not decreasing in RA's(captures)

[Buck Horn]

On 22.06.2022 at 06:52:13, Jagadeesh M via dnsmasq-discuss wrote:

So, as per our requirement we made dnsmasq to send only one prefix 
(clients should configure ipv6 address with only that prefix), we 
changed dhcp-range config in dnsmasq.


You haven't disclosed whether you'd run dnsmasq on your router or on a 
separate host.


Depending on your network setup, it may not be possible to fully address 
this by configuring dnsmasq alone.


If your dnsmasq would be running on a separate host in addition to your 
router, your router would remain a source of RAs for your clients, and 
quite likely the preferred one. If your router advertises a ULA prefix, 
your clients are going to consider that for IPv6 address construction as 
advertised.


I mean to say, always the valid and preferred lifetimes in RA(seen 
through captures) is constant at 86400. It is not decrementing and it 
is becoming a protocol violation.


Could you elaborate on that?

I do not see a protocol violaton here: RFC 4861 explicitly allows to 
advertise valid and preferred lifetimes as 'fixed time that stays the 
same in consecutive advertisements' as one of two ways, and it even 
defines that fixed time variant as a default.


Regards,
 Buck


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Re: [Dnsmasq-discuss] Valid and Preferred lifetimes are not decreasing in RA's(captures)

[Nothing New via Dnsmasq-discuss]

On Wed, Jun 22, 2022 at 10:22:13AM +0530, Jagadeesh M wrote:
> Hi,
> 
> Wanted your suggestion regarding a problem we are seeing with dnsmasq
> configuration.
> 
> At first, we had an issue where we did have dnsmasq sending RA's with
> multiple prefixes as we had multiple ipv6 addresses(with different
> prefixes) on the interface.
> So, as per our requirement we made dnsmasq to send only one prefix (clients
> should configure ipv6 address with only that prefix), we changed dhcp-range
> config in dnsmasq.
> 
> from
> *a. dhcp-range=::,constructor:eth0,ra-stateless,24*h (with this config,
> lifetimes are decrementing in clients properly)
> 
> to
> *b. dhcp-range=eth0,1234::,ra-stateless,24h*
> 
> But,* after changing configuration to type 'b'*, we observed that whenever
> the clients receive a new RA, the clients are updating lifetimes values
> back to 86400 seconds(valid and preferred lifetime values which we gave)
> I mean to say, always the valid and preferred lifetimes in RA(seen through
> captures) is *constant at 86400*. It is not decrementing and it is becoming
> a protocol violation.
> 
> Overall, our aim is to send only 1 ipv6 prefix in RA, even though we have
> multiple ipv6 addresses(with multiple prefixes) on the interface.
> Also, another question: Is there any dhcp-range configuration with which we
> can exclude sending ULA prefixes in RA ?
> 
> I tried to configure dhcp-range with other alternative ways, but nothing is
> working out.
> 
> Any help/suggestions would be highly helpful and appreciated.

Suggestion:  Try harder to explain the "problem".


-- 
Silence is hard to parse

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