CCIE R&S Written Overview: IPv6

IPv6 Overview

• Main motivation for IPv6 is lack of IPv4 address space

• IPv4 uses 32-bits (4 bytes)

– 2^32 = 4,294,967,296 max addresses

• IPv6 uses 128-bits (16 bytes)

– 2^128 = 34,028,236,692,938,463,463,374,607,431,770,00 0,000+

IPv4 vs. IPv6 Addressing Format

• IPv4 Dotted Decimal

– 1.2.3.4

– Each place denotes 1 byte

• IPv6 Hexadecimal

– XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX:XXXX

– Two characters = one byte

IPv6 Address Space

• Four main address types

– Global Unicast

• 2000… – 3FFF…

– Unique Local

• FC00…

• Deprecates Site Local (FEC0)

– Link Local

• FE80…

– Multicast

• FF…

Modified EUI-64 Addressing

• IPv6 host addresses are generated from interface MAC address

• MAC address is 48-bits

• IPv6 host address is 64-bits

• Extra 16 bits derived as follows:

– MAC 1234.5678.9012

– Invert 7th most significant bit

• 1034.5678.9012

– Insert “FFFE” in middle

• 1034:56FF:FE78:9012

IPv6 Address Resolution

• Ethernet

– ICMPv6 ND replaces ARP

• NBMA

– Static resolution on multipoint interfaces

– Inverse Neighbor Discover not implemented

ICMPv6 Neighbor Discovery

• ICMPv6 ND

• Replaces IPv4 ARP

• NS – Neighbor Solicitation

– Ask for information about neighbor

• NA – Neighbor Advertisement

– Advertise yourself to other neighbors

• RS – Router Solicitation

– Ask for information about local routers

• RA – Router Advertisement

– Advertise yourself as an active router

• Send neighbor solicitation to solicited node multicast

– FF02:0:0:0:0:1:FF00::/104 + 24 low-order bits

• If no reply address is unique

– Duplicate Address Detection (DAD)

• Send unsolicited neighbor advertisement to announce yourself

– Sent to all hosts multicast

• FF02::1

• Essentially the same as 255.255.255.255

IPv6 Routing Overview

• IPv6 unicast routing off by default

– ipv6 unicast-routing

• Dynamic routing through

– RIPng

– OSPFv3

– EIGRPv6

– IS-IS

– BGP

• Dynamic information recurses to remote link-local address

– Layer 3 to layer 2 resolution on multipoint NBMA medias

IPv6 Static Routing

• Same static routing implications as IPv4

– To next-hop

• Resolve next-hop

– To multipoint interface

• Resolve final destination

– To point-to-point interface

• No resolution required

IPv6 Routing

• RIPng, OSPFv3, & EIGRPv6

– Use separate processes

• BGP & IS-IS

– Use the same process

– Different Address families

RIPng Overview

• RFC 2080 – RIPng

• Similar in operation to RIPv1 / RIPv2

• UDP port 521 multicast to FF02::9

• Configuration

– Interface level ipv6 rip [process] enable

– Automatically enables global process

• Split-horizon enabled globally

– no split-horizon on multipoint NBMA

EIGRPv6 Overview

• Similar in operation to IPv4 EIGRP

• IP protocol 88 multicast to FF02::A

• Configuration

– Interface level ipv6 eigrp [ASN]

– Process level no shutdown

OSPFv3 Overview

• RFC 2740 – OSPFv3

• Similar in operation to OSPFv2

• Router-id is IPv4 address

– Use router-id command if no IPv4 configured

• Configuration

– Interface level ipv6 ospf [process-id] area [area-id]

– Automatically enables global process

OSPFv3 LSAs

• Most LSAs are the same as in OSPFv2

– LSA 1 – Router LSA

– LSA 2 – Network LSA

– LSA 3 – Inter-Area-Prefix-LSA

• Same as OSPFv2 Summary LSA

– LSA 4 – Inter-Area-Router-LSA

• Same as OSPFv2 ASBR Summary LSA

– LSA 5 – AS-External-LSA

– LSA 7 – Type-7-LSA

• Two new LSAs

– LSA 8 – Link-LSA

• Link-Local scope

• Used for link-local next-hop calculation

– LSA 9 – Intra-Area-Prefix-LSA

• Area scope

• Used to advertise global addresses of connected links

• LSA 1 & 2 are still used to build the graph of the network, but are now decoupled from the actual addresses on the links

OSPFv3 Network Types

• Same network types as OSPFv2

– Broadcast

• DR/BDR Election

– Non-broadcast

• DR/BDR Election

• Unicast updates to link-local address

– Point-to-point

– Point-to-multipoint

– Point-to-multipoint non-broadcast

• Unicast updates to link-local address

BGP for IPv6 Overview

• Same process for IPv4 and IPv6

– Uses address-family configuration

• Normal BGP rules apply

– Requires underlying IGP transport

– iBGP loop prevention

• Don’t advertise iBGP learned routes to other iBGP neighbors

• Exception through route-reflection / confederation

– EBGP loop prevention

• Don’t accept routes with your own AS in the path

– Same best-path selection process

Tunneling IPv6 over IPv4

• Static tunnels

– GRE

• Default tunnel mode

– IPv6IP

• Less overhead, but no CLNS transport

• Automatic tunnels

– IPv4 Compatible Tunnel

• IPv6 next-hop is IPv4 address, e.g. ::192.168.1.1

– Automatic 6to4

• Imbeds IPv4 address into IPv6 prefix to provide automatic tunnel endpoint determination

– ISATAP

• Automatic host to router and host to host tunneling

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