[Dnsmasq-discuss] IPv6 dhcp strangeness

Tue May 3 18:48:31 BST 2016

Hi Simon,

Thanks for getting back to me.  Kermit is a Windows Home Server box and
is definitely not net or dual booted.  Here's the relevant 'log dhcp'
extract from a clean boot of it. 

dhcp-host=id:00:01:00:01:1b:75:4c:36:e0:3f:49:a1:d4:aa,[::4],Kermit
dhcp-host=E0:3F:49:A1:D4:AA,192.168.219.4,kermit

Before booting:

nslookup kermit
nslookup: can't resolve '(null)': Name does not resolve

Name:      kermit
Address 1: 2001:470:183f:da2b::4 kermit.darbyshire-bryant.me.uk
Address 2: 192.168.219.4 kermit.darbyshire-bryant.me.uk

No entries in dhcp.leases.

Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
available DHCP range: 192.168.219.2 -- 192.168.219.253
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
vendor class: MSFT 5.0
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
client provides name: Kermit
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
DHCPREQUEST(br-lan) 192.168.219.4 e0:3f:49:a1:d4:aa
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
tags: lan, known, br-lan
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
DHCPACK(br-lan) 192.168.219.4 e0:3f:49:a1:d4:aa kermit
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
requested options: 1:netmask, 15:domain-name, 3:router, 6:dns-server,
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
requested options: 44:netbios-ns, 46:netbios-nodetype, 47:netbios-scope,
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
requested options: 31:router-discovery, 33:static-route,
121:classless-static-route,
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
requested options: 249, 43:vendor-encap
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 next
server: 192.168.219.1
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837
broadcast response
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  1 option: 53 message-type  5
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 54 server-identifier  192.168.219.1
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 51 lease-time  12h
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 58 T1  6h
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 59 T2  10h30m
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option:  1 netmask  255.255.255.0
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 28 broadcast  192.168.219.255
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option:  3 router  192.168.219.1
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option:  6 dns-server  192.168.219.1
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size: 23 option: 15 domain-name  darbyshire-bryant.me.uk
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size: 33 option: 81 FQDN  03:ff:ff:6b:65:72:6d:69:74:2e:64:61:72:62...
Tue May  3 18:40:57 2016 daemon.info dnsmasq-dhcp[2862]: 1035611837 sent
size:  4 option: 44 netbios-ns  192.168.219.1
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055
available DHCP range: 2001:470:183f:da2b::2 -- 2001:470:183f:da2b::ffff:ffff
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055 vendor
class: 311
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055
DHCPCONFIRM(br-lan) 00:01:00:01:1b:75:4c:36:e0:3f:49:a1:d4:aa
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055
DHCPREPLY(br-lan) 2001:470:183f:da2b::9f93:7b6a
00:01:00:01:1b:75:4c:36:e0:3f:49:a1:d4:aa Kermit
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055 tags:
known, dhcpv6, br-lan
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055 sent
size: 14 option:  1 client-id  00:01:00:01:1b:75:4c:36:e0:3f:49:a1:d4:aa
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055 sent
size: 14 option:  2 server-id  00:01:00:01:1e:b7:72:d8:14:cc:20:be:89:33
Tue May  3 18:40:58 2016 daemon.info dnsmasq-dhcp[2862]: 9972055 sent
size: 29 option: 13 status  0 all addresses still on link

Only Entry in dhcp.leases related to kermit

1462340457 e0:3f:49:a1:d4:aa 192.168.219.4 kermit 01:e0:3f:49:a1:d4:aa

Kermit thinks it has 2001:470:183f:da2b::9f93:7b6a as per the dhcp
reply, which is fair enough but I don't understand why the UID was
ignored.  Also, nslookup replies from dnsmasq still only return the
configured addresses for kermit and no sign of the dhcpv6 allocated one.

Ideas?

Kevin

On 02/05/2016 17:24, Simon Kelley wrote:
> On 30/04/16 11:32, Kevin Darbyshire-Bryant wrote:
>> Further clues maybe:  So initially when kermit comes up it grabs an IPv4
>> address and I see this entry in dnsmasq's lease database:
>> 1462055024 e0:3f:49:a1:d4:aa 192.168.219.4 Kermit 01:e0:3f:49:a1:d4:aa
>>
>> Which looks pretty normal to me.  Then a little while later, presumably
>> after a dhcpv6 request it gets changed to
>> 1462055060 e0:3f:49:a1:d4:aa 192.168.219.4 Kermit
>> 01:52:41:53:20:e0:3f:49:a1:d4:aa:00:00:09:00:00:00
>>
>> There are also syslog messages of "abandoning lease to e0:3f:49:a1:d4:aa
>> of 192.168.219.4" which I don't get at all.
>>
>>
> Are you dual-booting Kermit, or netbooting it, or doing anything else
> which may cause it to run more than one DHCP client? From the
> information given it looks like the host with MAC address
> e0:3f:49:a1:d4:aa is presenting two different client-ids at different
> times. Since client-id trumps MAC address as a unique host identifier,
> that could explain what's going on. (the client-id is the last field in
> the leases database).
>
> Setting log-dhcp and posting the logs showing this sort of thing
> happening would be useful.
>
> Cheers,
>
> Simon.
>
>
>> On 29/04/16 12:27, Kevin Darbyshire-Bryant wrote:
>>> Hi All,
>>>
>>>
>>> I've just noticed some strange/different behaviour with regard to
>>> dhcpv6 address allocation.  I've a couple of 'internal' machines that
>>> I'd like to have fixed ip addresses.  To that end, and it used to work
>>> I've got lines similar to: 
>>> dhcp-host=E0:3F:49:A1:D4:AA,192.168.219.4,[::0:4],Kermit   - In theory
>>> kermit gets 192.168.219.4 and the ipv6 address 'constructed prefix::0:4'
>>>
>>>
>>> Instead, these lines appear to be partially ignored with the host
>>> getting the usual pseudo random address constructed from the ipv6
>>> prefix/range.  An nslookup pointing to dnsmasq does return the '0:4'
>>> address, unfortunately that's not the address handed out by dhcp.  
>>> I'm also seeing ' abandoning lease to e0:3f:49:a1:d4:aa of
>>> 192.168.219.4' type warnings which is odd.  Also the entry in the
>>> leases database looks odd to me: 1461971298 e0:3f:49:a1:d4:aa
>>> 192.168.219.4 Kermit
>>> 01:52:41:53:20:e0:3f:49:a1:d4:aa:00:00:09:00:00:00 - that almost looks
>>> like an ipv6 type entry.
>>>
>>>
>>> Confused!
>>>
>>>
>>> Kevin
>>>
>>>
>>>
>>> _______________________________________________
>>> Dnsmasq-discuss mailing list
>>> Dnsmasq-discuss at lists.thekelleys.org.uk
>>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>>
>>
>> _______________________________________________
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-- 
Thanks,

Kevin at Darbyshire-Bryant.me.uk
M: +44 7947 355344 H: +44 1256 478597

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