Thursday, January 20, 2011

CCIE Study Guide: IPv6 Notes

IPv6 is a very hot topic these days, as the availability of IPv4 is coming to an end. The third part of our CCIE Study Guide Series and provides useful notes about IPv6.

• 128 bit addresses – eight 16bit hex fields
• Native support for mobile IP and IPSec
• Headers – 8
Version = 6
Traffic class = equivalent to IPv4 type of service
Flow label = allows packet to be labeled as part of a particular flow
Payload length = equivalent to the IPv4 total length field
Hop limit = similar to TTL
Next header = similar to the IPv4 protocol field
Source address/destination address = 128 bits each!
• Zero Compression
A double colon can be written to represent a block of zeros within the IP address.
Can only be used once in a given IPv6 address
Ex: 1234:1234:0000:0000:0000:0000:3456:3456
Ex: 1234:1234::3456:3456
• Leading Zero Compression
Leading zeros in each field can be eliminated
Can be used as many times as you’d like in a given address
Ex: 1234:1234:0000:0000:0000:0001:3456:3456
Ex: 1234:1234:0:0:0:1:3456:3456
Leading Zero and Zero compression can be used together
  • Ex: 1234:1234:0000:0000:0000:0001:3456:3456
  • Ex: 1234:1234::1:3456:3456
• Address types
Aggregatable global unicast address
  • Equal to IPv4 public address. This is a world routable address
Link local address
  • These addresses are specific to the physical link. I’m thinking this works similar to APIPA addresses in IPv4
Site local address
  • This is equivalent to RFC 1918 addresses in IPv4
• Initial bit identifiers
001 – global addresses
1111 1111 – multicast (FF) ff00::/8
1111 1110 11 – site local (FEC0)
1111 1110 10 – link local (FE80)
1111 1110 1 – signifies private IP space
::x.x.x.x – IPv4 compatible address. The first 96 bits are set to 0
::1 – loopback addresses equivalent to
::/128 – unspecified address
::/0 – default route/address
• SLA – site level aggregator works similar to an IPv4 subnet address
16 bits offering up to 65,000 subnets
• Packet types
Unicast – one to one communication
Multicast – one to many or many to one communication
Anycast – anycast addresses are assigned to multiple interfaces. When a host sends an anycast packet, it is received by the nearest member of the group only.
• Address assignments
IPv6 auto configuration is equal to IPv4 DHCP
  • Two types – stateful and stateless
  • Stateful – DHCPv6
  • Stateless – no server is used
         • I believe this works by the host sending a request to the local router/gateway and getting certain information from there.
         • Router solicitation and advertisement messages similar to NS/NA messages below. Sent to FF02::2 (all routers multicast)

Neighbor solicitation message is sent to make sure there are no dupes on a local segment. NS is multicast to FF02::1 (all nodes multicast)
Neighbor advertisement message is sent in response to an NS to inform of any dupes
• IPv6 Routing
Ipv6 unicast-routing global configuration command must be entered to use IPv6 in Cisco IOS
OSPFv3 – RFC 2740
  • Router ID has to be manually set under the OSPFv3 process. This is still a 32 bit value
  • R1(config-if)# ipv6 ospf process id area 0
  • R1(config)# ipv6 router ospf 1
  • R1(config-rtr)# router-id x.x.x.x
  • R1(config-rtr)# Pay attention to the router config prompt!!!!
RIPng – RIP new generation
IS-IS for IPv6
EIGRP for IPv6
Static routing
Multi Protocol BGPv4 (MPBGP4 or just MPBGP)
• IPv6 and IPv4 playing together
Dual stack – equipment runs both IPv4 and IPv6 stacks. I never really thought of this, but is there a metric or preference for systems running dual stack? For instance, if host 1 and host 2 were both running dual stacks, would they prefer one over the other?

6 to 4 tunneling – automatic, scalable, not always up.
  • This is used to tunnel IPv6 traffic over an IPv4 link
  • Reserved prefix of 2002:IPv4inhex::/48
  • R1(config)#interface fa 0/1
  • # ip addr
  • # interface tunnel 0
  • # ipv6 addr 2002:dcc8:112a::/48
  • Allows IPv6 hosts to talk to IPv4 hosts using NAT between the two.

    We are preparing some notes about how to configure NAT and hope to bring them to you soon.
Previous posts in our CCIE Study Guide Series were:

1 comment:

  1. Great thoughts you got there, believe I may possibly try just some of it throughout my daily life.

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