Extraneous Reply to Information Request for Stateless DHCPv6

[Paul Fitzgerald]

I may have identified the culprit. There were additional dhcpd daemons
running unnoticed.

On Sun, Mar 18, 2018 at 10:00 AM, Paul Fitzgerald <pgf at pgf.org> wrote:

> Hi all,
>
> I am working to configure stateless DHCPv6 on my network to provide DNS
> recursive name servers to Windows clients who have obtained their IPv6
> addresses using SLAAC.
>
> I am running into an issue that is introducing an inconsistency into the
> process that leads to an undesirable outcome. Basically, I'm seeing an
> extra Reply message from the DHCP server that doesn't include the DNS
> recursive name servers. If that Reply message is sent/received first, the
> client's DNS servers are not set properly.
>
> I'm currently using ISC DHCP Server 4.1-ESV-R8.
>
> I've tried various permutations, but this is my current dhcpd.conf
>
> option dhcp6.name-servers 2001:4860:4860::8888, 2001:4860:4860::8844;
>
> shared-network LANv6 {
>     subnet6 2603:xxxx:xxxx:d0e0::/64 {
>     }
> }
> shared-network WLANv6 {
>     subnet6 2603:xxxx:xxxx:d0e1::/64 {
>     }
> }
>
> I am seeing the Information-Request message from the client:
>
> DHCPv6
>     Message type: Information-request (11)
>     Transaction ID: 0xf4de56
>     Client Identifier
>         Option: Client Identifier (1)
>         Length: 14
>         Value: 0001000121c9bf4c0056cd39a752
>         DUID: 0001000121c9bf4c0056cd39a752
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Dec 17, 2017 17:50:36.000000000 Central Standard Time
>         Link-layer address: 00:56:cd:39:a7:52
>     Option Request
>         Option: Option Request (6)
>         Length: 4
>         Value: 00170018
>         Requested Option code: DNS recursive name server (23)
>         Requested Option code: Domain Search List (24)
>     Elapsed time
>         Option: Elapsed time (8)
>         Length: 2
>         Value: 0000
>         Elapsed time: 0 ms
>
> Then I see *two* Reply messages from the server. If the first message
> contains the DNS recursive name servers, all is well. Otherwise, the name
> servers are not configured as expected.
>
> DHCPv6
>     Message type: Reply (7)
>     Transaction ID: 0xf4de56
>     Client Identifier
>         Option: Client Identifier (1)
>         Length: 14
>         Value: 0001000121c9bf4c0056cd39a752
>         DUID: 0001000121c9bf4c0056cd39a752
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Dec 17, 2017 17:50:36.000000000 Central Standard Time
>         Link-layer address: 00:56:cd:39:a7:52
>     Server Identifier
>         Option: Server Identifier (2)
>         Length: 14
>         Value: 00010001223e067e44d9e79e3682
>         DUID: 00010001223e067e44d9e79e3682
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Mar 15, 2018 23:37:18.000000000 Central Daylight Time
>         Link-layer address: 44:d9:e7:9e:36:82
>     DNS recursive name server
>         Option: DNS recursive name server (23)
>         Length: 32
>         Value: 200148604860000000000000000088882001486048600000...
>          1 DNS server address: 2001:4860:4860::8888
>          2 DNS server address: 2001:4860:4860::8844
>
> DHCPv6
>     Message type: Reply (7)
>     Transaction ID: 0xf4de56
>     Client Identifier
>         Option: Client Identifier (1)
>         Length: 14
>         Value: 0001000121c9bf4c0056cd39a752
>         DUID: 0001000121c9bf4c0056cd39a752
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Dec 17, 2017 17:50:36.000000000 Central Standard Time
>         Link-layer address: 00:56:cd:39:a7:52
>     Server Identifier
>         Option: Server Identifier (2)
>         Length: 14
>         Value: 00010001224015df44d9e79e3683
>         DUID: 00010001224015df44d9e79e3683
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Mar 17, 2018 13:07:27.000000000 Central Daylight Time
>         Link-layer address: 44:d9:e7:9e:36:83
>
> Any idea why I'm getting the extra Reply message or how I can eliminate it?
>
> Thanks!
>
> Paul Fitzgerald
>
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