Category: IPv6

IPv6 Review

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


  • Link-local scope address:  layer2 domain
  • Unique / Site-local scope address: Organization
  • Global scope address: Internet



  • Transition technique designed to allow native IPv6 hosts to access IPv4-only content.
    • (Translation technique not a tunneling technique).
  • Primarily used to allow v6 hosts to initiate connections to IPv4 content.
    • Mechanisms do exist to allow the reverse.
  • Stateful and stateless versions.
    • stateful can use any prefix
    • stateless has restriction on prefix

NAT64 and DNS64 co-existance.

  1. IPv6 host sends AAAA DNS Query
  2. DNS64 server tries AAAA lookup and fails
  3. DNS64 server successfully resolves IPv4 address
  4. DNS64 server generates AAAA DNS response of <IPv6 prefix:IPv4 adress> and sends it back to the client.


IPv6 Tunnels

  • point-to-point tunnels
  • MCT ( manually configured tunnel )
  • GRE ( Generic Routing Encapsulation )
  • Virtual point-to-point between two IPv4 routers
  • IPv6 iGP routing protocols can run over these virtual links.


IPv6 iGP redistribution

Similarities to IPv4

  • Redistribution takes routes from the IP routing table, not from the iGP databases.
  • Route maps can be used for filtering, metrics, route tags.
  • Admnistrative distance has not changed.
  • Options to prevent routing loops; Administrative distance, route tags, filtering.
  • Syntax is the same.

Differences to IPv4

  • Supported “match” commands in route-maps vary on iGP
    • OSPF/RIP cannot match op “route-type” with a Route-map
      • EIGRP has no problems using “route-type”
    • Route-map matching IPv6 ACLs must have IPv6 prefix as source portion and “any” as destination of ACL.
  • IPv6 redistribute connected does not include interfaces running the iGP;
    • redistribute include-connected






  • UPD port number 521
  • No autosummarization for IPv6
  • Destination address FF02::9
  • Link-Local next-hops
  • IPv6 uses IPv6 AH/ESP Authentication
  • Enable it on the interface
    • ipv6 rip CCNP enable fa0/0
  • No network command


  • EIGRP uses the neighbor’s link local address as the next-hop
  • Destination FF02::AA
  • Authentication relies on the IPv6 built-in authentication nad privacy
  • IPv4 defaults to auto summarization, IPv6 doesn’t
    • ipv6 unicast-routing
    • ipv6 route eigrp 100
    • (config-if)#ipv6 eigrp 100
    • eigrp router-id RID