Magoo's Wise Words
CCNP Study guides

Posted:
23 Aug 07

 

 

 


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IPv6

 

  1. Features

    1. Larger address space

      1. 128 bits

      2. Allows large allocations - leads to better summarization

    2. Simplified header

      1. 40 octets (compared to 20)

      2. fewer fields - 7 compared to 12

      3. next header extension field

    3. mobility and security

    4. stateless auto-configuration

    5. MTU auto-discovery - performed every 5 minutes

    6. transition mechanisms

  2. Addresses

    1. 3 main types

      1. Unicast

        1. Global unicast (or global aggregateable) - 2001::/16 currently being allocated

        2. link-local - FE80::/10

        3. identifies a single interface

      2. Anycast - delivered to closest interface configured with that anycast address

      3. Multicast

      4. No broadcast addresses

    2. Each interface has multiple addresses

      1. At least one loopback (::1) and one link-local address

      2. may also have other global or local addresses

    3. Interface identifier (EUI-64 format)

      1. based on Layer2 information

      2. On Ethernet:

        1. Based on MAC address

        2. Insert 0xFFFE between upper 3 bytes (OUI) and lower 3 bytes

        3. 7th bit in high -order byte set to 1 to indicate uniqueness (Universal/Local bit)

    4. Global Unicast Addresses

      1. 48-bit global routing prefix - Assigned by IANA through local registries (ex ARIN)

      2. 16-bit subnet ID - Assigned by organizations to create addressing hierarchy

      3. 64-bit interface ID - usually the Interface identifier

    5. Link-Local

      1. limited scope (local link)

      2. dynamically created on all IPv6 interfaces

      3. uses FE80::/10 and 64-bit interface ID

      4. used for neighbor discovery, auto address configuration, router discovery, and routing protocols

    6. Multicast addresses

      1. Subset of global unicast with FF00::/8 prefix

      2. second octet defines the lifetime or scope

        1. Flag - first nibble

          • 0 for permanent and well-know addresses

          • 1 for temporary addresses

        2. Scope - second nibble

          • 1 - interfaces

          • 2 - link-local

          • 3 - subnet-local

          • 4 - admin-local

          • 5 - site-local

          • 8 - Org local

          • E - Global

      3. Some Well-known addresses

        1. FF02::1 - All nodes on a link

        2. FF02::2 - All routers on a link

        3. FF02::1:FFXX:XXXX - Solicited-node

          • XX:XXXX is the least significant 24-bits of IP of a node.

          • Used to determine link layer address of solicited node, as in Ipv4 ARP

    7. Stateless Auto-configuration

      1. Routers periodically sent “router advertisements” to the “all nodes” multicast address. Clients can use the router's source address to determine the link prefix and the router address to use as a gateway

      2. clients can also send a “router solicitation” to the “all routers” multicast ip to request a router solicitation.

      3. Hosts combine the link prefix with their 64-bit interface ID to make a full IP address

  3. Header

    1. Fields

      1. version - 6

      2. Traffic class - similar to T0S. Used for QOS.

      3. Flow Label

        1. new to v6

        2. 20 bits

        3. tagged by source of the packet

        4. allows multilayer switches to handle traffic per-flow rather than per-packet and provides QOS

      4. Payload length

      5. Next header

        1. Similar to Protocol field in v4

        2. Points to a transport-layer packet or an extension header

      6. Hop limit

        1. same as TTL

        2. no checksum in v6 header, so routers can decrement hop limit without recomputing a checksum

      7. source address

      8. Destination add

      9. Extension headers

        1. Processed in the order they appear in the packet

        2. usually only processed by destination except hop-by-hop header

        3. Types

          • Hop-by-hop

          • destination options - used in mobile IPv6

          • Routing header - used for source routing and mobile IPv6

          • Fragment header

          • Authentication header and ESP header

          • Upper-layer header (TCP or UDP)

  4. Mobility

    1. Normal “home address” maintained while moving

    2. “care-of” address bound to home address while moving between mobile nodes

    3. uses IPv6 mobility extension header

    4. dynamic home agent address discovery mechanism returns a single reply to the mobile node. directed broadcast in Ipv4 returns separate replies from each home agent

  5. Transitioning

    1. Dual stack

      1. node chooses stack based on destination address - prefers IPv6

      2. ipv6 unicast-routing global command enables forwarding of IPv6

      3. ipv6 address address/prefix-length [eui-64] interface command assigns IP

    2. Tunneling

      1. IPv6 is tunneled over IPv4 using IPv4 protocol 41

      2. manual tunnel

        1. configure a dual-stack edge router on each end

        2. manually build a tunnel with an IPv6 address and “tunnel mode ipv6ip”

      3. 6to4 tunneling

        1. 2002::/16 + hex of IPv4 address assigned to edge router

        2. routers recognize the meaning of these IP's and automatically tunnel packets when next hop is IPv4

      4. ISATAP - treats IPv4 link as a virtual IPv6 link and maps addresses between versions

      5. Teredo - automatic UDP tunneling technique that claims to be able to cross NAT

    3. IPv4 addresses in IPv6

      1. IPv4 Compatible IPv6 addresses

        1. embeds IPv4 address in lower 32 bits (::/96) ex - ::192.168.1.1

        2. these addresses are deprecated

      2. IPv4 mapped IPv6 IP addresses

        1. ::ffff:0:0/96 w/IPv4 address in lower 32 bits. ex - ::ffff:192.168.1.1

        2. represented in either dotted decimal or colon hex notation

        3. dual stack nodes sending traffic to IPv4 hosts recognize the meaning of these addresses and send IPv4 packets (no encapsulation)

    4. Translation

      1. NAT-PT can be used to connect an IPv4 network to an IPv6 network

      2. Stateless IP/ICMP Translation translates header fields

      3. translations can be mapped statically or dynamically using dns and a DNS-application layer gateway

      4. Bump-in-the-API and Bump-in-the-Stack can translate on an IPv6 host for IPv4 upper-layer applications (although this is know to be unreliable)

  6. Routing Protocols

    1. Static

      1. specify next-hop add using link-local address, not global unicast

      2. ipv6 route prefix/prefix-length global configuration command

    2. RIPng

      1. 15 hop limit, split-horizon, poison reverse

      2. uses link-local addresses as source address

      3. multicast add FF02::9 as destination

      4. UDP port 521

    3. OSPFv3

      1. permits multiple sessions per interfaces

      2. supports authentication using IPsec within IPv6

      3. runs on a link rather than a subnet

      4. runs directly over IPv6 rather than TCP

      5. uses link-local addresses for protocol communication

      6. router ID and area ID remain 32 bits in dotted decimal format

      7. header

        1. includes Instance ID to support multiple instances per link

        2. eliminates authentication fields and relies on IPv6 for authentication

        3. 16 bytes vs 24 in v2

        4. addresses moved to the payload

      8. multicast addresses

        1. FF02::5 - all spf routers

        2. FF02::6 - All DR's

      9. LSA's

        1. Types

          • 1 - Router-LSA - 0x2001

          • 2 - Network-LSA - 0x2002

          • 3 - Inter-Area-Prefix-LSA - 0x2003

          • 4 - Inter-Area-Router-LSA - 0x2004

          • 5 - Autonomous system-external-lsa

          • 6 - group-membership-lsa

          • 7 - type-7-lsa (nssa)

          • 8 - link-lsa

            • show ipv6 ospf [process-id] database link

          • 9 - intra-area-prefix-lsa

            • show ipv6 ospf [process-id] database prefix

        2. characteristics

          • 32 bit router ID, area id, and link-state id in dotted decimal format

          • link-local, area, and AS flood scopes

          • support for forwarding of unknown LSA's based on flood scope (useful in NSSA)

      10. Configuration

        1. ipv6 cef global command (recommended)

        2. ipv6 router ospf process-id global command

        3. router-id router-id(required)

        4. ipv6 ospf process-id area area-id [instance instance-id] interface command (not “network x.x.x.x area x.x.x.x”)

        5. area area-id range prefix/prefix-length router configuration command (summarization)

        6. most other commands are the same - just change “ip” to “ipv6”

    4. IS-IS

      1. 2 new TLV's

        1. IPv6 reachability

        2. IPv6 interface address

    5. EIGRP

    6. MP-BGP4

      1. includes a new identifier for the IPv6 addresses

      2. NEXT_HOP attrib contains a global IPv6 address and also has a link-local address when there is local link connection between peers

  7. Sources

    1. Cisco BSCI Authorized Self-Study Guide

    2. Sybex CCNP Complete

    3. Wikipedia

    4. RFC 4291

    5. Cisco BSCI Official Exam Certification Guide

Back to BGP - Up to index - Next to Multicast
Updated:
23 Aug 07

 

 

 


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