Understanding Basic Concepts and Addressing

Rationale for IPv6

There is an IP address shortage
  • USA is still sitting pretty
  • Asia and Africa received single class C for entire country
Current IP address poorly allocated
  • Agencies needing class C asked for class B
  • Estimates on IPv4 exhaustion largely debated (2009 - 2041)
New Network Devices on the rise
NAT (our current solution) is now seen as a hinderence to innovation
Potential Future features:IPSec everywhere, Mobility, Simpler Header

These features are cool but not business motivator.

IPv6 Addressing Format

  • Address size moved from 32bit (IPv4) to 128bits (IPv6)
  • To make addresses more manageale, divided into 8 groups of 4 hex characters each
  • Rule1 : eliminate groups of consecutive zeros
  • Rule2 : drop leading zeros

IPv6 headers and Address Types

Types of Communication

  • Unicast: one-to-one
  • Multicast : one-to-many
  • Anycast : one-to-closest

Types of Addresses

  • Link-local scope address : Layer 2 domain
  • Unique/site-local scope address : organization - equivalent to private IPv4 address
  • Global scope address : internet
Link Local Addresses
  • Assigned automatically as an IPv6 host comes online
  • Similar to the 169.254.x.x addresses of IPv4
  • Always begin with FE80 (first 10 bits : 1111 1110 10) followed by 54 bits of zeros
  • Last 64 bits is the 48 bit mac address with FFFE squeeze in the middle.
MAC ADDRESS : 0019.D122.DCF3


Unique-local (RFC4193) / Site-local (RFC3512) Addresses
  • Unique Local is the new name of Site Local address
  • The purpose of this address has been argued extensively
  • Used within enterprise networks to identify the boundary of their networks
  • Uses the following format:
    • begin with FC00::/7 = 1111 110(L)
    • bit 8 is :
      • 1 = Locally Assigned
      • 0 = Future Use
    • 40 bits : Global ID
    • 16 bits : Subnet ID
    • 64 bits : Interface ID
  • Currently, the site addresses begin with FD00::/8.
Global Addresses
  • Have their high-level 3 bits set to 001 (2000::/3)
  • Global routing prefix is 48 bits or less
  • Subnet ID is comprised of whatever bits are left over after global routing prefix
  • The primary addresses expected to comprise the IPv6 Internet are from the 2001::/16 subnet.
Multicast Addressing
  • Unlike IPv4, Multicasting is huge in IPv6
  • First 8 bits are always FF
  • Flag currently has 4 bits defined (ORPT)
  • Scope Defines how fare the multicast goes
    • 1 - interface
    • 2 - link
    • 3 - subnet
    • 4 - admin
    • 5 - site
    • 8 - organization
    • E - global
  • Some Well Know (permenant) Multicast Addresses
    • FF02::1 - All nodes (on link)
    • FF02::2 - All routers (on link)
    • FF02::9 - All RIP routers (on link)
    • FF02::1:FFxx:xxxx - an IPv6 "ARP" message (on link)
    • FF05::101 - All NTP servers (within site)

Configuring, Routing, and Interoperating

Assigning IPv6 addresses

R1(config)# int s0/0.4
R1(config-subif)# ipv6 address 2001:210:10:1::1/64
R1(config-subif)# ipv6 enable

Check the configuration

R1# show ipv6 int brief
Serial0/0.4                                 [up/up]

Serial interface does not have mac address, so it stole it from an Ethernet interface.

Test connectivity

R1# ping ipv6 2001:210:10:1::2

Check the routing table

R1# show ipv6 route

IPv6 routing protocols

In addition to static routing, nearly every routing protocol has been updated to support IPv6
  • RIPng
  • OSPFv3
  • EIGRP for IPv6
  • IS-IS for IPv6
  • MP-BGP4
OSPFv3... What's new ?

1. Smaller header (16 vs 24 bytes) - no authentication. Aunthentication is done thanks to IPSec.
2.No network statement
3. All neighbor communication through Link-local address (this communication now seperate)
4. Multiple OSPF "instances" per link... In odd network designs, one link could belong to multiple area
5.New multicast addresses : FF02::5 - FF02::6
6.No authentication

Base configuration of OSPFv3

Start OSPFv3. There is no more network command on the router config mode.
R3(config)# ipv6 unicast-routing
R3(config)# ipv6 router ospf 10
R3(config-rtr)# router-id
Configure OSPv3 per interface
R3(config)# int fa0
R3(config-if)# ipv6 ospf 10 area 0
R3# show ipv6 ospf
R3# show ipv6 ospf neighbor
R3# show ipv6 ospf interface
R3# show ipv6 route
O   1FE0:1111::/32 [110/65]
     via FE80::201:42FF:FE2C:4DEE, Serial0

IPv4 to IPv6 migration strategies

Technology exists to provide a smooth, non-pressured transition
  • Dual-Stack routers
  • Tunneling (6to4 and 4to6)
  • NAT Protocol Translation (NAT-PT)