Address Autoconfiguration

1
Address Autoconfiguration

• Feng Zou
• SW2
• ZyXEL Communications Corp.
• 04/11/2006

2
Outline

• Why We Need Address Autoconfiguration?
• IPv6 Address Structure Review
• How to Autoconfiguration?
• Autoconfiguration Process
• Autoconfigured Address States
• Types of Autoconfiguration
• QA

3
Why We Need Address Autoconfiguration?

• The size of an address in IPv6 is 128 bits
• Each interface have multiple IPv6 addresses
• Its difficult to configure those IP addresses
  manually

MAC 00-B0-D0-23-47-33 FE802B0D0FFFE234733
(link-local address) FEC0F2822B0D0FFFE2347
33 (site-local address) 3FFE2900D005F2822B0D0
FFFE234733 (global address) FF021FF23
4733 (solicited-node address)
Host A
4
IPv6 Address Structure Review

• Link-local address
• FE80 XXXXXXXXXXXXXXXX
• (Fixed Prefix) (Interface ID)

5
IPv6 Address Structure Review

• Site-local address
• FEC0 SSSS XXXXXXXXXXXXXXXX
• (Fixed) (Subnet ID)
• Prefix
  (Interface ID)

6
IPv6 Address Structure Review

• Aggregatable global address
• Prefix Interface ID

7
IPv6 Address Structure Review

• Solicited-node address
• FF021FF XXXXXX
• (Fixed Prefix) (last 24 bits of Interface ID)

64 bits
64 bits
Interface ID
Unicast prefix
104 bits
24 bits
FF02
1FF
0000
XXXXXX
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How to Autoconfigure Address

• IPv6 address Prefix Interface ID
• Interface ID is converted from MAC
• Link-local address
• Prefix FE80 is fixed
• Can be determined even without a router and a
  DHCPv6 server
• Site-local address ,aggregatable global address
• Prefix can be determined by Prefix Information
  options in Router Advertisement message
• Other configuration parameters
• Other configuration parameters include hop limit,
  reachable time, retransmission timer, MTU
• Can be determined by Router Advertisement message

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Autoconfiguration Process

• For IPv6 node
• 1. Derive tentative link-local address based on
  FE80/64 and a EUI-64-derived Interface ID.
• 2. Using Duplicate Address Detection to verify
  the uniqueness of the tentative link-local
  address.
• 3. If a Neighbor Advertisement message is
  received, address auto-configuration stops.
  Manual configure or assign a new Interface ID
  (must do Duplicate Address Detection either) to
  this interface.
• 4. If NO Neighbor Advertisement message is
  received, the tentative link-local address is
  valid and the link-layer multicast address of the
  corresponding solicited-node address is
  registered.

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Autoconfiguration Process

• For IPv6 host
• 1. The host sends a Router Solicitation message.
• 2. If NO Router Advertisement messages are
  received, the host uses a stateful address
  auto-configuration protocol to obtain addresses
  and other configuration parameters.
• 3. If a Router Advertisement message is received,
  the host sets configuration parameters (hop
  limit, reachable time, retransmission timer,
  MTU).

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Autoconfiguration Process

• 4. For each Prefix Information option present
• If the On-Link flag is set to 1, the prefix is
  added to the prefix list.
• If the Autonomous flag is set to 1, the prefix
  and an appropriate Interface ID are used to
  derive a tentative address.
• Use duplicate address detection to verify the
  uniqueness of the tentative address.
• If the tentative address is in use, dont use the
  address to initialize the interface.
• If the tentative address is not in use, the
  address is initialized. If needed, registers the
  new link-layer multicast address of the
  corresponding solicited-node address.
• 5. If the Managed Address Configuration flag is
  set to 1, a stateful address auto-configuration
  protocol is used to obtain additional addresses.
• 6. If the Other Stateful Configuration flag is
  set to 1, a stateful address auto-configuration
  protocol is used to obtain additional
  configuration parameters.

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• Ethernet Header
• Destination MAC is 33-33-FF-23-47-33
• IPv6 Header
• Source Address is
• Destination Address is FF021FF234733
• Hop limit is 1
• Multicast Listener Report Header
• Multicast Address is FF021FF234733

? Send Multicast Listener Report
Multicast Listener Report
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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• Ethernet Header
• Destination MAC is 33-33-00-00-00-02
• IPv6 Header
• Source Address is
• Destination Address is FF022
• Hop limit is 255
• Router Solicitation Header

? Send Router Solicitation
Router Solicitation
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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• Ethernet Header
• Destination MAC is 33-33-FF-23-47-33
• IPv6 Header
• Source Address is
• Destination Address is FF021FF234733
• Hop limit is 255
• Neighbor Solicitation Header
• Target Address is FE802B0D0FFFE234733

? Send Neighbor Solicitation
Neighbor Solicitation
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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• Ethernet Header
• Destination MAC is 33-33-00-00-00-01
• IPv6 Header
• Source Address is FE80210FFFFFED658C0
• Destination Address is FF021
• Hop limit is 255
• Router Advertisement Header
• Current Hop Limit 64
• Router Lifetime 1800
• Source Link-Layer Address is 00-10-FF-D6-58-C0
• Prefix Information is for FEC000F282
• Valid Lifetime 2592000
• Preferred Lifetime 604800
• Prefix Information is for 3FFE2900D005F282

Router Advertisement
? Send Router Advertisement
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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• Ethernet Header
• Destination MAC is 33-33-FF-23-47-33
• IPv6 Header
• Source Address is
• Destination Address is FF021FF234733
• Hop limit is 255
• Neighbor Solicitation Header
• Target Address is FEC0F2822B0D0FFFE234733

? Send Neighbor Solicitation
Neighbor Solicitation
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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• Ethernet Header
• Destination MAC is 33-33-FF-23-47-33
• IPv6 Header
• Source Address is
• Destination Address is FF021FF234733
• Hop limit is 255
• Neighbor Solicitation Header
• Target Address is 3FFE2900D005F2822B0D0FFFE2
  34733

? Send Neighbor Solicitation
Neighbor Solicitation
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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? NO Neighbor Advertisement message received
MAC 0010FFD658C0 IP FE80210FFFFFED658C0 FE
C000F282210FFFFFED658C0 3FFE2900D005F28
2210FFFFFED658C0
Router
Host B
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Autoconfigured Address States

• Tentative
• The address is in the process of being verified
  as unique
• Valid
• An address from which unicast traffic can be sent
  and received
• Preferred state
• An address for which uniqueness has been
  verified, unrestricted use
• Deprecated state
• An address that is still valid, but is
  discouraged for new communication
• Invalid
• An address for which a node can no longer send or
  receive unicast traffic

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Autoconfigured Address States
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Types of Autoconfiguration

• Stateless
• Receipt of Router Advertisement messages with one
  or more Prefix Information options
• Stateful
• Use of a stateful address configuration protocol
  such as DHCPv6
• Both
• Receipt of Router Advertisement messages and
  stateful configuration protocol
• For all types, a link-local address is always
  configured automatically.

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• Q A

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IPv6 Training Courses
27
IPv6 Training Courses