IPV6 link local address

Guys could any tell that why link local address is configured in Lab 6 task 6.2 while it is not mention in the task?

Also the frame-relay mapping is already been configured between R1, R2 & R5 in previous task using the global address.

Comments

  • the reason con fingure explicitly FE80::x in an interface is for ease of configuration and troubleshooring.

    Dynamic routing protocols user the link local address and not the global unicast address thats why you have to map also de link local address in frame relay besided of the global unicast address. There is no Inverse-ARP for IPV6 so you need to map both , global unicast address and link local.

    HTH

     

    Santiago E

     

     

  • ok. If dynamic routing protocol uses ths link local address, then whats the need  to configure global unicast address.

  • The link-local address can only be used between directly connected network nodes. The same link-local address can be used on multiple links, which would cause confusion if the link-local address were used across the network - which interface was the packet destined for?, etc.

    It would also be permissible for a different device to use the same link-local address on a different link, as long as the same address is not used by more than one device on the same link. Router A could use FE80::1 on a link to Router B and Router C  could use FE80::1 on a different link connected to Router A, as long as Router A used some different link-local address for communication with Router C.

    If you look at show ipv6 route you will see:

    L   FE80::/10 [0/0]
         via ::, Null0

    Each router will route to null0 all packets addressed to any link-local address that cannot be processed locally by the router. Non-link-local addresses (global or site-wide) addresses are required for IPv6 packets to be forwarded by routers.

  • Is it neccessary to map both Link-local address and Globally unicast address in frame-relay map command. Isnt it sufficient enough to map only globally unique address? Why mapping link-local address is important ?

     

  • Dear Experts,

    Perhaps I have got the answer, could you pls verify:

    Yes, its important to map link-local address also, as the next hop to reach the destination across frame-relay is the link-local address.

    One more point, I beleive in IPv6 frame-relay, its not important to you broadcast key word in the frame-relay map command, as there is no concept of broadcast in IPv6.

    Kindly correct if I am wrong...

  • ASHSE - But there is multicast in IPv6. How are you planing to
    establish a neighbor adj over NBMA without "neighbor" command?

    -Andrius
  • ashe,

    If you are using static routing, the unicast IPv6 address mapping to the frame-relay DLCI would be sufficient.

    However, OSPFv3 uses the link-local address for peering/next-hop, so if there is no mapping to a DLCI, either through a specific frame-relay map statement, or using a point-to-point subinterface, which requires no mapping, the OSPF routers will not form adjacencies, and no routes will be learned or propagated over the frame-relay links.

    This link points to an OSPFv3/NBMA example in the 12.4 documentation: http://www.cisco.com/en/US/docs/ios/ipv6/configuration/guide/ip6-ospf.html#wp1071230

    Is it neccessary to map both Link-local address and Globally unicast address in frame-relay map command. Isnt it sufficient enough to map only globally unique address? Why mapping link-local address is important ?

     

     

  • ashe,

    Multicast over frame-relay for IPv6 is handled similarly to broadcast/multicast over frame-relay for IPv4 - the broadcast keyword needs to be configured on one frame-relay map statement per DLCI per protocol.

    As in IPv4 configuration, if multiple frame-relay map statements are used for the same DLCI, only one map statement needs the "broadcast" keyword.

    This means that you can configure the broadcast keyword either on the global unicast mapping, or on the link-local mapping - it is not needed on both.

    Dear Experts,

    One more point, I beleive in IPv6 frame-relay, its not important to you broadcast key word in the frame-relay map command, as there is no concept of broadcast in IPv6.

    Kindly correct if I am wrong...

     

  • Thnx Darell, for a clear and nice explanation. Appreciate much

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