[Dibbler] DHCPv6 Client DUID question

Schauer, Paul E Paul_Schauer at cable.comcast.com
Thu Jan 25 21:19:51 CET 2007


I am using the Dibbler DHCPv6 client to request a static IPv6 address
from an ISC DHCPv6 server. The client is running on Red Hat Linux. I am
seeing the following issue on eth0:

/var/lib/dibbler/client-duid
00:01:00:00:45:b6:70:0a:00:06:5b:29:f4:9a

tcpdump of a DHCPv6 lease request from the dibbler client:

tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size
65535 bytes
00:23:10.131702 IP6 (hlim 64, next-header: UDP (17), length: 88)
fe80::206:5bff:fe29:f49a.dhcpv6-client > ff02::1:2.dhcpv6-server: [udp
sum ok] dhcp6 solicit (xid=f3b9e6 (client ID hwaddr/time type 0 time
1169584138 00065b29f49a0000b00f0409) (IA_NA IAID:1 T1:4294967295
T2:4294967295 (IA_ADDR :: pltime:4294967295 vltime:4294967295)) (elapsed
time ?))
        0x0000:  6000 0000 0058 1140 fe80 0000 0000 0000
`....X. at ........
        0x0010:  0206 5bff fe29 f49a ff02 0000 0000 0000
..[..)..........
        0x0020:  0000 0000 0001 0002 0222 0223 0058 36c0
.........".#.X6.
        0x0030:  01f3 b9e6 0001 0014 0001 0000 45b6 700a
............E.p.
        0x0040:  0006 5b29 f49a 0000 b00f 0409 0003 0028
..[)...........(
        0x0050:  0000 0001 ffff ffff ffff ffff 0005 0018
................
        0x0060:  0000 0000 0000 0000 0000 0000 0000 0000
................
        0x0070:  ffff ffff ffff ffff 0008 0004 0000 0000
................

The DUID reported in the packet dump contains the client DUID in the
message starting at position 0x0038. There is additional information
starting at position 0x0046 (0x0000b00f0409) in the DUID construct. This
information plus the client DUID equals the correct length (0x0014)
listed in the packet, but I cannot find a reference in RFC3315 for what
this information might represent.

This information changes between restarts of the client. Therefore,
making a static IP reservation in the DHCPv6 server is impossible
because the client DUID changes each time the client restarts.

Has anyone seen this behavior? Is there an explanation for the extra
part of the client DUID in the message?

Thank you,
Paul Schauer


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