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.


Show interface tunnel
show ipv6 interface brief

  • Create a loopback interface
  • assign an IPv4 adress
  • create an ‘interface tunnel’ with logical number
    • tunnel source
    • tunnel mode ipv6ip
    • add IPv6 adress to the tunnel


  • difference is tunnel mode
    • If you don’t configure a tunnel mode command it falls back to GRE
    • tunnel mode gre ip

6to4 tunnels

  • 6to4 tunnels do no support IPv6 iGP.
  • 6to4 tunnels are multipoint


  • Intra-Site Automatic Tunnel Addressing Protocol
  • ISATAP is designed for transporting IPv6 packets within a site
  • Can use any unicast IPv6 prefix (/64) and the IPv4 adress is encoded in the last 32bits of the IPv6 address
    • First 32bits contain the value 0000:5RER to indicate it’s an ISATAP adress.
    • Last 32bits contain the IPv4 adress.
    • FE80::000:5efe::32bitIPv4Addr

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