Question about DHCPv6 Lease Selection

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Question about DHCPv6 Lease Selection

John W. Blue

https://www.isc.org/wp-content/uploads/2017/08/dhcp43clientconf.html

 

“In the DHCPv6 protocol the client will wait a small amount of time to allow ADVERTISE messages from multiple servers to arrive.”

 

If only one server responds and the dhclient gives it a score of zero, what options do you have to force to accept?


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RE: Question about DHCPv6 Lease Selection

John W. Blue

And here is the advertise packet in question that is generating a score of zero.  Any thoughts as to why it got a zero?

 

Frame 13: 182 bytes on wire (1456 bits), 182 bytes captured (1456 bits)

Ethernet II, Src: Cisco_6d:28:d9 (e0:2f:6d:6d:28:d9), Dst: Vmware_ba:a7:4c (00:0c:29:ba:a7:4c)

Internet Protocol Version 6, Src: fe80::e22f:6dff:fe6d:28d9, Dst: fe80::20c:29ff:feba:a74c

User Datagram Protocol, Src Port: 547, Dst Port: 546

DHCPv6

    Message type: Advertise (2)

    Transaction ID: 0xc28475

    Client Identifier

        Option: Client Identifier (1)

        Length: 14

        Value: 0001000123bd8128000c29baa74c

        DUID: 0001000123bd8128000c29baa74c

        DUID Type: link-layer address plus time (1)

        Hardware type: Ethernet (1)

        DUID Time: Dec 31, 2018 19:38:48.000000000 Central Standard Time

        Link-layer address: 00:0c:29:ba:a7:4c

    Server Identifier

        Option: Server Identifier (2)

        Length: 14

        Value: 0001000155d45514f8bc123d6ca8

        DUID: 0001000155d45514f8bc123d6ca8

        DUID Type: link-layer address plus time (1)

        Hardware type: Ethernet (1)

        DUID Time: Aug 18, 2045 05:06:12.000000000 Central Daylight Time

        Link-layer address: f8:bc:12:3d:6c:a8

    DNS recursive name server

        Option: DNS recursive name server (23)

        Length: 32

        Value: 20010578003f0000000000000000001020010578003f0001...

         1 DNS server address: 2001:578:3f::10

         2 DNS server address: 2001:578:3f:1::10

    Identity Association for Non-temporary Address

        Option: Identity Association for Non-temporary Address (3)

        Length: 40

        Value: 29baa74c0000a8c000010e000005001820010579ff010100...

        IAID: 29baa74c

        T1: 43200

        T2: 69120

        IA Address

            Option: IA Address (5)

            Length: 24

            Value: 20010579ff01010028d37d19b1c2def60001518000015180

            IPv6 address: 2001:579:ff01:100:28d3:7d19:b1c2:def6

            Preferred lifetime: 86400

            Valid lifetime: 86400

 

From: dhcp-users [mailto:[hidden email]] On Behalf Of John W. Blue
Sent: Friday, January 04, 2019 9:38 AM
To: [hidden email]
Subject: Question about DHCPv6 Lease Selection

 

https://www.isc.org/wp-content/uploads/2017/08/dhcp43clientconf.html

 

“In the DHCPv6 protocol the client will wait a small amount of time to allow ADVERTISE messages from multiple servers to arrive.”

 

If only one server responds and the dhclient gives it a score of zero, what options do you have to force to accept?


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Re: Question about DHCPv6 Lease Selection

Simon Hobson
John W. Blue <[hidden email]> wrote:

> And here is the advertise packet in question that is generating a score of zero.  Any thoughts as to why it got a zero?

Probably not related since DUIDs are supposed to be treated as blobs, and the client shouldn't really have a reason to look inside and decode them ...

>     Server Identifier
>         Option: Server Identifier (2)
>         Length: 14
>         Value: 0001000155d45514f8bc123d6ca8
>         DUID: 0001000155d45514f8bc123d6ca8
>         DUID Type: link-layer address plus time (1)
>         Hardware type: Ethernet (1)
>         DUID Time: Aug 18, 2045 05:06:12.000000000 Central Daylight Time

That date is "quite a long time" into the future. Not impossible that it's being rejected as impossible - but as I say, there isn't really any reason for the client to be inspecting this.


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