Host Autoconfiguration
ALTTC, Ghaziabad
IPv4 Address and IPv6 equivalents
IPv4 Address
IPv6 Address
Internet address classes
Not application in IPv6
Multicast addresses (224.0.0.0.0/4)
IPv6 multicast addresses (FF00::/8)
Broadcast addresses
Not applicable in IPv6
Unspecified addresses is 0.0.0.0
Unspecified address is ::
Loopback address is 172.0.0.1
Loopback address is ::1
Public IP addresses
Global unicast addresses
Private IP addresses
(10.0.0.0/8,172.16.0.0/12)
Unique local (FD00::/8) or site-local
addresses (FEC0::/10) (deprecated)
APIPA addresses ( 169.254.0.0/16)
Link-Local addresses (FE80::/64)
Text representation: Dotted-decimal notation Text representation: colon hexadecimal
format with suppression of leading zero
and zero compression
Prefix representation: subnet mask in
dotted-decimal notation or prefix length
notation.
Prefix representation: prefix length
notation only.
ALTTC, Ghaziabad
Methods of Configuration of the Host
Manual
Host
Configuration
Auto
ALTTC, Ghaziabad
Autoconfiguration
Stateful
Stateless
Types of the Autoconfiguration
Autoconfiguration
Option
Stateless
Stateful
DHCPv6
Both
ALTTC, Ghaziabad
IPv6
IPv6 Address Example
An IPv6 address can have different states
Tentative address- This is an address that has not
yet been defined ie the state prior to the
assignment
Preferred Address-This is an address that has been
defined to an interface & can be used without any
restriction.
Deprecated address-The address whose life time is
about to expire & no longer be used as a source
address for newly established connection
IPv6
IPv6 Address Representation EUI 64
IPv6 uses the extended universal identifier (EUI)-64
format to do stateless autoconfiguration.
This format expands the 48-bit MAC address to 64 bits by
inserting “FFFE” into the middle 16 bits.
To make sure that the chosen address is from a unique
Ethernet MAC address, the universal/local (U/L bit) is set
to 1 for global scope (0 for local scope).
IPv6
IPv6 Address Representation EUI 64
IPv6
Stateless Autoconfiguration Example
MAC address: 00:0A:AC:01:C9:1C
EUI 64 Address: 20A:ACFF:FE01:91C
Some OS compute random number using MAC to
create 64bit unique Interface Id (masking MAC)
The prefix for link-local addresses is FE80::/64.
Local Link Address becomes
FE80::20A:ACFF:FE01:91C/64
Stateless Autoconfiguration Example
If Unique Local Network Prefix given by Router is
FC00::1/64,
The Unique Local Address Becomes:
FC00::1 :20A:ACFF:FE01:91C/64
Stateless Autoconfiguration Example
Router Solicitation is sent on FF01::2 (All Router
Multicast Address) and Advertisement sent on
FF01::1 (All Node Multicast Address)
Source : FE80::20A:ACFF:FE01:91C/64
Destination: FF02::2
Source : Router Interface Address
Destination: FF02::1
Stateless Autoconfiguration Example
Following steps are performed , when node is
autoconfigured.
A link local address is generated by using link local prefix
FE80::/64 & an EUI-64 derived interface identifier. It is in
tentative state.
The node joins the multicast group (FF02::1) the all node
multicast group & the solicit node multicast groupfor the
tentative address
A neighbor solicitation message is sent out with the tentative
address as the target address
If a neighbor advertisement message is received , indicates
that another node is on the local link is using the tentative
address & the address autoconfiguration stop & manual
configuration must be performed.
Stateless Autoconfiguration Example
If no neighbor advertisement message is received
,the tentative link local address is assumned to be
unique & valid & then asssigned to the interface. The
state of the address changes to “PREFFERED”
In order to determine the Router ,the host sends a
router solicitation message to the all router multicast
group FF02::2 ie request all routers connected to the
link to send a router advertisement message for prefix
information
All routers on the link reply with a router
advertisement & host generate an address by
combining the prefix with the interface identifier.
Stateless Autoconfiguration Example
Router periodically send RA. Host senda a
router solicitation message to request an
immediate RA rather than waiting the next
RA
If no RA message is received, the host uses the
address configuration protocol to obtain
address & other configuration parameters.
If RA is received , the hop limit, MTUreachacle
time etc. parameters are set.
Stateless Autoconfiguration
Stateless Address Configuration (IP Address, Default
Router Address)
Routers sends periodic Router Advertisement
Node gets prefix information from the Router
advertisement and generates the complete address
using its MAC address
Global Address=Link Prefix + EUI 64 Address
Router Address is the Default Gateway
Stateless Autoconfiguration Example
Using Link-Local Address, Router Solicitation is sent by
Host on FF02::2 (All Router Multicast Address)
Router sends Advertisement on FF02::1 (All Node
Multicast Address)
If Global Unicast Network Prefix given by Router is
2001:db8::23:1/64,
The Global Unicast Address Becomes:
2001:db8::23:1 :20A:ACFF:FE01:91C/64
IPv6
DHCPv6
Stateful Configuration
Provides not only IP address, also other configuration
parameters like DNS
IPv6
DHCPv6
DHCP uses the following multicast address.
All_DHCP_Relay_Agents_and_Servers)
FF02::1:2
All DHCP agents (server & relay) are
member of this multicast group. DHCP
client use this multicast address to reach
DHCP agent
DHCPv6
Client
Initiates requests on a link to obtain
configuration parameters
use its link local address to connect the server
Send requests to FF02::1:2 multicast address
(All_DHCP_Relay_Agents_and_Servers)
DHCPv6
Relay Agent/ DHCPv6 Server
node that acts as an intermediary to deliver
DHCP messages
between clients and servers
is on the same link as the client
Is listening on multicast addresses:
All_DHCP_Relay_Agents_and_Servers (FF02::1:2)
DHCPv6
The following UDP ports are used with DHCPv6:
UDP port 546 (client port)
DHCP servers use this port as the destination
port to reach DHCP relays or DHCP client. Used
by DHCP relay agents as the destination port to
reach DHCP clients.
UDP port 547; Agent port
DHCP clients use this port as the destination
port to reach DHCP agents. DHCP relays use this
port as the destination port to reach DHCP
server.
Client Server Message Exchange


Typical 4 message exchange sequence
 Solicit from client
 Advertise from server
 Request from client
 Reply from Server
Typical 2 message exchange sequence
 Information Request from client
 Reply from server
ALTTC, Ghaziabad
DHCPv6 Client Messages





Solicit (1)- Used by the clients to locate DHCP server
Advertise(2)- Used by the server as a response to
Solicit
Request (3)- Used by the clients to get information
from server
Confirm (4)- Used by the clients to verify that their
addresses & configuration parameters are still valid
Renew (5)- Used by the client to renew the
configuration
ALTTC, Ghaziabad
DHCPv6 Client Messages




Rebind (6)- Used bye the client to extend the
lifetime of their addresses
Reply(7)- Used by the DHCP server responding to
Request, Confirm, Rebind , Release & decline
messages
Release (8)- Used by the client to release their
addrerssses.
Decline (9)
ALTTC, Ghaziabad
DHCPv6 Server Messages



Reconfigure (10)- Used by the DHCP sever to inform
clients that server has new or updated information
Information(11)
Relayed messages
– Relay Forward (12)
Used bye the DHCP relay to forward client
messages to server.
– Relay Reply (13)
Used by DHCP server to send messages to client
through relay.
ALTTC, Ghaziabad
Thanks!
ALTTC, Ghaziabad