CCIE – RS – L3 Technologies – Addressing Technologies – IPv6

Identify, Implement and Troubleshoot IPv6 Addressing and Subnetting


128 bit address

16 byte hexadecimal number, separated by colons :

  • Leading zeros in the address field are optional
  • Pair of colons :: represents successive field of zeros
    • Can only be used once in an address

Prefixes

  • Made up of leftmost bits and act as the network identifier
  • Use / prefix-length > decimal value
  • 2001:db8:8086:6502::/64

Address Types

  • Unicast
    • Address for a single interface
    • Packet sent to a unicast address is delivered to the interface identified with that address
  • Anycast
    • Address for a set of interfaces
    • Typically belonging to different nodes
    • Delivered to closest interface, defined by the routing protocols in use
  • Multicast
    • Address for a set of interfaces (in a given scope)
    • Typically belonging to different nodes
    • Packet is delivered to all interfaces identified by the multicast address

There is no concept of broadcast

Address Management and Assignment

  • Static configuration
    • Manually defined host address, mask and gateway
    • Disables autoconfiguration
  • Stateless Address Autoconfiguration (SLAAC)
    • Hosts autonomously configure its own address
    • Uses Router Solicitation, sent during booting up to request a Router Advertisement (RA) to configure its interface
    • RFC 2462
    • No DHCP server is needed
    • Address is formed by combining network prefixes with interface identifier
    • Information is provided to all nodes on local link
    • Makes renumbering a network easy
  • Stateful DHCPv6
    • Uses DHCP to get IPv6 address
    • Uses multicast for many of the messages
    • Clients use Neighbor Discovery to find routers on the link
      • RA responds if DHCP should be used
      • Client starts DHCP solicitation
  • Stateless DHCP
    • Host uses SLAAC and DHCP to get additional parameters, such as:
      • TFTP, WINS, etc.

Interface can have more than 1 IPv6 address per interface

Transitions

  • Dual Stack
    • Requires infrastructure to support IPv4 and IPv6
    • Applications choose between IPv4 and IPv6 based on response to DNS requests
  • Tunneling
    • Encapsulates IPv6 traffic within an IPv4 packet
    • Used between IPv6 sites over an IPv4 backbone
    • Tunneling Techniques
      • ISATAP
      • Teredo
      • 6PE
      • 6VPE
      • mGRE v6 over v4
    • Manual or automatically configured
  • Translation

 


Unicast, Multicast

Global Unicast – 2000::/3

Link Local Uniacst – FE80::/10

Unique Local – FC00::/8 , FD00::/8

Multicast – FF00::/8

  • All Nodes, Link Local: FF02::1
  • All Routers, Link Local: FF02::1
  • All OSPF Routers: FF02::5
  • All OSPF DR routers: FF02::6
  • All ISIS routers: FF02::8
  • All RIP Routers: FF02::9
  • All EIGRP routers: FF02::A
  • All PIM routers: FF02::D
  • MLDv2 Reports: FF02::16

https://tools.ietf.org/html/rfc2375

 


EUI-64

RFC 2373

  • Allows host to assign itself a unique 64bit v6 interface identifier
  • Obtained through 48bit MAC
    • MAC is separated into (2) 24bits (OUI and NIC)
    • 16bit value – FFFE is inserted between 2 fields

Screen Shot 2016-08-29 at 8.32.45 PM.png


ND, RS/RA

Neighbor Discovery

  • Uses ICMP messages and solicited node multicast
  • Neighbor Solicitation
    • Type 135
    • Sent on local link when node wants to determine link-layer address of another node on the same local link
    • Can also be used to verify reachability of a neighbor
    • Neighbor Advertisement
      • Sent when three is a change in the link-layer address of a node

Router Advertisement

  • Type 134 of ICMP packet header
  • Periodically sent out each configured interface
    • Sent using all-nodes multicast address
  • For Stateless autoconfiguration to work, advertised prefix length must always be 64bits
  • Ipv6 unicast-routing – enables RA automatically on ethernet and FDDI interfaces
  • No ipv6 nd ra suppress – enables RA on interface manually
  • Ipv6 nd ra suppress – disables RA on interface

Neighbor Redirect

  • Type 137
  • Inform host of better first-hop nodes on path to a destination

Autoconfig / SLAAC temporary addresses (RFC4941)

Stateless Address Autoconfiguration (SLAAC)

  • Hosts autonomously configure its own address
  • Uses Router Solicitation, sent during booting up to request a Router Advertisement (RA) to configure its interface
  • RFC 2462
  • No DHCP server is needed
  • Address is formed by combining network prefixes with interface identifier
  • Information is provided to all nodes on local link
  • Makes renumbering a network easy

Global Prefix Configuration Feature

Simplifies network renumbering and allows for automated prefix definition

Ipv6 general-prefix [name] [ipv6prefix/prefix-length]

Device(config)# ipv6 general-prefix my-prefix 2001:DB8:2222::/48

 

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipv6/configuration/15-2mt/ip6-15-2mt-book/ip6-generic-prefix.html


DCHP Protocol Operations

Stateful DHCPv6 – RFC3315

Enables DHCP server to send configuration parameters to IPv6 hosts, ex: DNS, NTP, etc.

DUID – DHCPv6 Unique Identifier, used to identify the device when exchanging DHCP messages

https://www.cisco.com/c/en/us/products/collateral/ios-nx-os-software/enterprise-ipv6-solution/whitepaper_c11-689821.html


SLAAC / DHCPv6 Operations

SLAAC

Device picks it’s own address based on the prefix being advertised by the connected interface.

Uses EUI-64 address format

  • Host sends a router solicitation message
  • Hosts waits for a Router Advertisement message
  • Hosts take the first 64 bits of the IPv6 prefix from the Router Advertisement message and combines it with the 64 bit EUI-64 address to createa global unicast message. The host also uses the source IP address, in the IP header, of the Router Advertisement message, as its default gateway
  • Duplicate Address Detection (DAD) is performed by IPv6 clients in order to ensure that random address is unique

SLAAC / DHCPv6 Interaction

RFC3736

Uses SLAAC for address assignment and DHCPv6 for additional parameters that are not assigned with SLAAC (DNS, NTP, TFTP, etc)

DHCPv6 server does not keep track of the address assignments


Stateful, Stateless DHCPv6

Stateful DHCPv6

  • Uses DHCP to get IPv6 address
  • Uses multicast for many of the messages
  • Clients use Neighbor Discovery to find routers on the link
  • RA responds if DHCP should be used
  • Client starts DHCP solicitation

Stateless DHCP

  • Host uses SLAAC and DHCP to get additional parameters, such as:
  • TFTP, WINS, etc.

DHCPv6 Prefix Delegation

RFC3633 – https://tools.ietf.org/html/rfc3633

Extension of DHCPv6

DHCPv6-PD assigns a set of IPv6 subnets

“These options would be used by a service provider to assign a prefix to a Customer Premise Equipment (CPE) device acting as a router between the subscriber’s internal network and the service provider’s core network.” from RFC

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