DHCPv6 and MAC Address inclusion
Michael Dean Pugh
mdpugh at hotmail.com
Thu Jan 26 01:56:10 UTC 2012
At the risk of stating the obvious, here is a Wireshark capture of a DHCPv6
Solicit from host Charm:
No. Time Source Destination Protocol
Length Info
109 20.586056 fe80::204:23ff:fea5:e1f4 ff02::1:2 DHCPv6
167 Solicit XID: 0xed672f CID: 0001000113777c7300d0b7e8ce8f
Frame 109: 167 bytes on wire (1336 bits), 167 bytes captured (1336 bits)
Ethernet II, Src: Intel_a5:e1:f4 (00:04:23:a5:e1:f4), Dst:
IPv6mcast_00:01:00:02 (33:33:00:01:00:02)
Internet Protocol Version 6, Src: fe80::204:23ff:fea5:e1f4
(fe80::204:23ff:fea5:e1f4), Dst: ff02::1:2 (ff02::1:2)
User Datagram Protocol, Src Port: dhcpv6-client (546), Dst Port: dhcpv6-server
(547)
DHCPv6
Message type: Solicit (1)
Transaction ID: 0xed672f
Elapsed time
Option: Elapsed time (8)
Length: 2
Value: 0000
elapsed-time: 0 ms
Client Identifier: 0001000113777c7300d0b7e8ce8f
Option: Client Identifier (1)
Length: 14
Value: 0001000113777c7300d0b7e8ce8f
DUID type: link-layer address plus time (1)
Hardware type: Ethernet (1)
Time: May 7, 2010 21:35:47 Eastern Daylight Time
Link-layer address: 00:d0:b7:e8:ce:8f
Identity Association for Non-temporary Address
Option: Identity Association for Non-temporary Address (3)
Length: 12
Value: 0a0004230000000000000000
IAID: 0a000423
T1: 0
T2: 0
Fully Qualified Domain Name
Option: Fully Qualified Domain Name (39)
Length: 27
Value: 0005436861726d0e436f6d50756768546572576f72780363...
0000 0... = Reserved: 0x00
.... .0.. = N bit: Server should perform DNS updates
.... ..0. = O bit: Server has not overridden client's S bit preference
.... ...0 = S bit: Server should not perform forward DNS updates
Domain: Charm.ComPughTerWorx.com
Vendor Class
Option: Vendor Class (16)
Length: 14
Value: 0000013700084d53465420352e30
Enterprise ID: Microsoft (311)
vendor-class-data: "MSFT 5.0"
Option Request
Option: Option Request (6)
Length: 8
Value: 0018001700110027
Requested Option code: Domain Search List (24)
Requested Option code: DNS recursive name server (23)
Requested Option code: Vendor-specific Information (17)
Requested Option code: Fully Qualified Domain Name (39)
And here is the ipconfig/all output after it gets the IPv6 addresses:
PS C:\Windows\system32> ipconfig /all
Windows IP Configuration
Host Name . . . . . . . . . . . . : Charm
Primary Dns Suffix . . . . . . . : ComPughTerWorx.com
Node Type . . . . . . . . . . . . : Hybrid
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : ComPughTerWorx.com
Ethernet adapter Local Area Connection 2:
Connection-specific DNS Suffix . : ComPughTerWorx.com
Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Dual Port Server
Adapter #2
Physical Address. . . . . . . . . : 00-04-23-A5-E1-F5
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : fd00:a00::5(Preferred)
Lease Obtained. . . . . . . . . . : Wednesday, January 25, 2012 8:12:47 PM
Lease Expires . . . . . . . . . . : Monday, February 06, 2012 8:12:46 PM
Link-local IPv6 Address . . . . . : fe80::204:23ff:fea5:e1f5%18(Preferred)
IPv4 Address. . . . . . . . . . . : 10.0.0.5(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Monday, January 23, 2012 1:28:22 AM
Lease Expires . . . . . . . . . . : Thursday, February 02, 2012 4:21:47 AM
Default Gateway . . . . . . . . . : fe80::215:17ff:fe7c:d101%18
fe80::204:23ff:fea9:5b83%18
10.0.0.100
DHCP Server . . . . . . . . . . . : 10.0.0.1
DHCPv6 IAID . . . . . . . . . . . : 452985891
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-77-7C-73-00-D0-B7-E8-CE-
8F
DNS Servers . . . . . . . . . . . : fd00:a00::2
fd00:a00::1
10.0.0.1
10.0.0.2
NetBIOS over Tcpip. . . . . . . . : Enabled
Connection-specific DNS Suffix Search List :
ComPughTerWorx.com
Ethernet adapter Local Area Connection:
Connection-specific DNS Suffix . : ComPughTerWorx.com
Description . . . . . . . . . . . : Intel(R) PRO/1000 MT Dual Port Server
Adapter
Physical Address. . . . . . . . . : 00-04-23-A5-E1-F4
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IPv6 Address. . . . . . . . . . . : fd00:ac10::5(Preferred)
Lease Obtained. . . . . . . . . . : Wednesday, January 25, 2012 8:13:03 PM
Lease Expires . . . . . . . . . . : Monday, February 06, 2012 8:13:03 PM
Link-local IPv6 Address . . . . . : fe80::204:23ff:fea5:e1f4%16(Preferred)
IPv4 Address. . . . . . . . . . . : 172.16.0.5(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Sunday, January 22, 2012 6:07:23 PM
Lease Expires . . . . . . . . . . : Monday, January 30, 2012 6:02:51 PM
Default Gateway . . . . . . . . . : fe80::203:47ff:fe72:33fc%16
fe80::207:e9ff:fe1b:5516%16
172.16.0.100
DHCP Server . . . . . . . . . . . : 172.16.0.1
DHCPv6 IAID . . . . . . . . . . . : 167773219
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-13-77-7C-73-00-D0-B7-E8-CE-
8F
DNS Servers . . . . . . . . . . . : fd00:ac10::1
fd00:ac10::2
172.16.0.1
172.16.0.2
NetBIOS over Tcpip. . . . . . . . : Enabled
Connection-specific DNS Suffix Search List :
ComPughTerWorx.com
Tunnel adapter IP6Tunnel:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . :
Description . . . . . . . . . . . : Microsoft Direct Point-to-point Adapater
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
Tunnel adapter isatap.ComPughTerWorx.com:
Media State . . . . . . . . . . . : Media disconnected
Connection-specific DNS Suffix . : ComPughTerWorx.com
Description . . . . . . . . . . . : Microsoft ISATAP Adapter
Physical Address. . . . . . . . . : 00-00-00-00-00-00-00-E0
DHCP Enabled. . . . . . . . . . . : No
Autoconfiguration Enabled . . . . : Yes
PS C:\Windows\system32>
Notice that the DUID is the same in each case (0001000113777c7300d0b7e8ce8f--
Wireshark calls it "client identifier"), but the MAC address that Wireshark
extracts from it (00:d0:b7:e8:ce:8f) does NOT match either MAC address
returned by ipconfig (00-04-23-A5-E1-F5 and 00-04-23-A5-E1-F4). This is
because Windows (2008 R2 in this case) created the DUID when a different
physical adapter was installed in the machine. When I replaced the adapter,
the DUID remained the same. So it seems the DUID is useless for getting the
accurate MAC.
Now, look at the IAIDs returned by Wireshark and ipconfig for Local Area
Connection (second one listed). 167773219 (decimal) is 0a000423 (hex) and
000423 is the first 24 bits of the MAC address of Local Area Connection.
Also, the IAID of LAC2 is 452985891, which is 1b000423 in hex, and the same
relationship exists between IAID and MAC. This is an example of how the
manufacturer portion of the MAC doesn't vary between interfaces.
Nevertheless, Windows distinguishes between them with the first 8 bits of the
IAID (0a vs. 1b). The reason I'd like to know how these bits are derived is
that they may be a function of the remaining 24 bits of the MAC. If this is
the case, it won't be in one-to-one correspondence with the MAC in general but
is highly likely to be so within a given host. I don't know if this will
solve any of the problems mentioned in this thread, but I thought I'd throw it
out there.
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