IPv6

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IPv6

• DHCPv6
• DNS

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Implementing DHCP for IPv6

• http//tools.ietf.org/html/rfc3315

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Methods for Autoconfiguration in IPv6

• One of the many enhancements introduced in IPv6
  is an overall strategy for easier administration
  of IP devices, including host configuration.
• Two basic methods defined for autoconfiguration
  of IPv6 hosts
• Stateless Autoconfiguration
• A method defined to allow a host to configure
  itself without help from any other device.
• Problem it does not supply a DNS server address.
• Stateful Autoconfiguration
• A technique where configuration information is
  provided to a host by a server.

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Protocols and Addressing

• The operation of DHCPv6 is similar to that of
  DHCPv4, but the protocol itself has been
  completely rewritten.
• It is not based on the older DHCP or on BOOTP,
  except in conceptual terms.
• It still uses UDP but uses
• new port numbers,
• a new message format, and
• restructured options.
• DHCPv6 is not compatible with DHCPv4 or BOOTP.

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DHCP Message Exchanges

• DHCP servers receive messages from clients using
  a reserved, link-scoped multicast address.
• A DHCP client transmits most messages to this
  reserved multicast address, so that the client
  need not be configured with the address or
  addresses of DHCP servers.
• Two basic client/server message exchanges used in
  DHCPv6
• Four-message exchange
• Two-message exchange

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DHCP Message Exchanges- Four Message Exchange

• When a client needs to obtain an IPv6 address and
  other parameters ? Client sends a Solicit message
• Similar to the regular DHCP address allocation
  process
• The client sends a multicast Solicit message to
  all-DHCP-Agent Multicast address (FF0212) to
  find a DHCPv6 server and ask for a lease.
• Any server that can fulfill the client's request
  responds to it with an Advertise message.
• The client chooses one of the servers and sends a
  Request message to it asking to confirm the
  offered address and other parameters.
• The server responds with a Reply message to
  finalize the process.

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DHCP Message Exchanges Two-message exchange

• When a DHCP client does not need to have a DHCP
  server assign it IP addresses, the client can
  obtain configuration information such as a list
  of available DNS servers or NTP servers through a
  single message and reply exchanged with a DHCP
  server.
• To obtain configuration information the client
  first sends an Information-Request message to the
  All_DHCP_Relay_Agents_and_Servers multicast
  address.
• Servers respond with a Reply message containing
  the configuration information for the client.

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DHCPv6 Operations
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DHCPv6 Multicast Addresses

• All_DHCP_Relay_Agents_and_Servers (FF0212)
• A link-scoped multicast address used by a client
  to communicate with neighboring (i.e., on-link)
  relay agents and servers.
• All servers and relay agents are members of this
  multicast group.
• All_DHCP_Servers (FF0513)
• A site-scoped multicast address used by a relay
  agent to communicate with servers, either because
  the relay agent wants to send messages to all
  servers or because it does not know the unicast
  addresses of the servers.
• Note that in order for a relay agent to use this
  address, it must have an address of sufficient
  scope to be reachable by the servers.
• All servers within the site are members of this
  multicast group.

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DHCPv6 UDP Ports

• Clients listen for DHCP messages on UDP port 546.
  
• Servers and relay agents listen for DHCP messages
  on UDP port 547.

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DHCPv6 Basic Message Format Types

• SOLICIT
• ADVERTISE
• REQUEST
• CONFIRM
• RENEW
• REBIND
• REPLY

• RELEASE
• DECLINE
• RECONFIGURE
• INFORMATION-REQUEST
• RELAY-FORW
• RELAY-REPL

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DHCPv6 Option Format Base Options

• Authentication
• Server Unicast
• Status Code
• Rapid Commit
• User Class
• Vendor Class
• Vendor-specific Information
• Interface-Id
• Reconfigure Message
• Reconfigure Accept

• Client Identifier
• Server Identifier
• Identity Association for Non-temporary Addresses
• Identity Association for Temporary Addresses
• IA Address
• Option Request
• Preference
• Elapsed Time
• Relay Message

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Differences between DHCP for IPv4 and IPv6

• Hosts always have a link local address that can
  be used in requests (in IPv4 0.0.0.0 is used as
  source address)
• Uses special multicast addresses for relay agents
  and servers
• No compatibility with BOOTP, since no BOOTP
  support on IPv6.
• Simplified two-message exchange for simple
  configuration cases
• A client can request multiple IPv6 addresses
• Client can send multiple unrelated requests to
  the same or different servers
• There is a reconfigure message where servers can
  tell clients to reconfigure. This feature is
  optional.

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Domain Name System (DNS)
Paul Mockapetris invented the DNS in 1983.
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How important is the DNS?

• Getting the IP address of the remote endpoint is
  necessary for every communication between TCP/IP
  applications
• Humans are unable to memorize millions of IP
  addresses (specially IPv6 addresses)
• To a larger extent DNS provides applications
  with several types of resources (domain name
  servers, mail exchangers, reverse lookups, )
  they need DNS design
• hierarchy
• distribution
• redundancy

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Approximate geographical position of all DNS root
name servers in February 2007
http//www.icann.org/maps/board-staff.htm http//w
ww.icann.org/maps/root-servers.htm
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TLDs and IPv6

• One of IANAs functions is the DNS Top-Level
  Delegations (TLDs)
• Changes in TLDs (e.gccTLDs) has to be approved
  and activated by IANA
• Introduction of IPv6-capable name servers at
  ccTLDs level has to be made through IANA

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DNS Lookup
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DN structure

• Resource Record (RRs) Data records stored by
  name servers.
• Types of RRs
• Start of Authority (SOA)
• Marks the beginning of a DNS zone
• Name Servers (NS)
• Doma name of a server in a DNS zone
• Canonical Names (CNAMEs)
• Aliases for FQDN
• Pointer (PTR)
• Aliase for another location in the domain name
  space.
• Resolver
• Host resovling a Ip address-to-name mapping

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DNS Lookup
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DNS for IPv6

• To expand the functionality of DNS to IPv6, three
  aspects to be considered
• Define a new record to store the 128-bit IPv6
  address
• Define IPv6 equivalent for in-addr.arpa.com
  domain for IPv4 PTR
• Define changes to Query messages and method of
  transporting them between Resolver and NS

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The Quad A Record(AAAA)

• Similar to A Resource Record for IPv4 (RFC3596)
• Holds the IPv6 Record for a host
• Entered into zone file in standard representation
• Backward compatible with (most) non-IPv6 aware
  resolvers (ignored RR type)

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Configuring AAAA record on Cisco IOS
Configuring router to query DNSv6 server
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Reverse DNS lookup

• Reverse DNS lookups for IPv6 addresses use
  similarly the special domain ip6.arpa which is
  special Top-Level Domain (TLD).
• An IPv6 address is represented as a name in the
  ip6.arpa domain by a sequence of nibbles in
  reverse order, represented as hexadecimal digits,
  separated by dots with the suffix .ip6.arpa.

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DNS software changes

• BIND 8 AAAA Resource records, no native IPv6
  transport (patch available)
• BIND 9 All currently defined IPv6 record types,
  native IPv6 transport
• djbns AAAA RR only, IPv6 transport only with
  patch
• NSD as per BIND 9

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IPv6 DNS and root servers

• DNS root servers are critical resources!
• 13 roots aroundthe world (10 in the US)
• Not all the 13 servers already have IPv6 enabled
  and globally reachable via IPv6.
• Need for (mirror) root servers to be installed in
  other locations (EU, Asia, Africa, )
• New technique anycastDNS server
• To build a clone from the master/primary server
• Containing the same information (files)
• Using the same IP address
• Such anycastservers have already begun to be
  installed
• F root server Ottawa, Paris(Renater), Hongkong,
  Lisbon (FCCN)
• Look at http//www.root-servers.org for the
  complete and updated list.

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DNS IPv6-capable software

• BIND (Resolver Server)
• http//www.isc.org/products/BIND/
• BIND 9 (avoid older versions)
• On Unix distributions
• ResolverLibrary ( (adapted) BIND)
• NSD (authoritative server only)
• http//www.nlnetlabs.nl/nsd/
• Microsoft Windows (Resolver Server)

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DNSv6 Operational Requirements Recommendations

• The target today IS NOT the transition from an
  IPv4-only to an IPv6-only environment
• How to get there?
• Start by testing DNSv6 on a small network and get
  your own conclusion that DNSv6 is harmless, but
  remember
• The server (host) must support IPv6
• And DNS server software must support IPv6
• Deploy DNSv6 in an incremental fashion on
  existing networks
• DO NOT BREAK something that works fine
  (production IPv4 DNS)!

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Host Name-to-Address Mappings Configuration
Example

• Defines two static host name-to-address mappings
  in the host name cache
• Establishes a domain list with several alternate
  domain names to complete unqualified host names,
• Specifies host 3FFEC002508BFFFEE8F800 and
  host 3FFE80A00F0041 as the name servers, and
  re enables the DNS service

• ipv6 host cisco-sj 3FFE70020112
• ipv6 host cisco-hq 2002C01F7681
  3FFE70020122
• ip domain-list csi.com
• ip domain-list telecomprog.edu
• ip domain-list merit.edu
• ip name-server 3FFEC002508BFFFEE8F800
  3FFE80A00F0041
• ip domain-lookup

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Q A