Forum Replies

1. Hi AD,

   Link-local addresses are only used on the local link. These addresses are not routable and used only for things like neighbor discovery or to establish OSPF / EIGRP neighbor adjacencies and such.

   The idea behind IPv6 is that every device connected to the Internet should have a global unicast address. NAT/PAT for IPv4 were only “tricks” to get around the lack of available IPv4 addresses.

   On your own networks, you could use the unique local addresses in the fc00::/7 range. These are equal to IPv4 private range addresses.

   Rene

2. Hello Sanjiv.

   In order to clarify why you’re getting the error, first let’s look back on how a router chooses its router ID. A router ID is always in the format of an IPv4 address. The router ID is chosen in the following order:

   1. If a router ID is configured in the ospf configuration, this is used as the router ID.
   2. If no router ID is configured, then it uses the highest IP address of a loopback interface
   3. If no loopback interface exists, it will use the highest IP address of any physical interface in the “up” state.

   Now if you’re using IPv4, then one of the a

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3. Can I ask what is the difference between the following 2 commands?

   “ospfv3 1 ipv6 area 0”
   “ipv6 ospf 1 area 0”

   I just tried this and it shows up differently under the running config:

   interface Ethernet0/0
   no ip address
   shutdown
   ipv6 enable
   ospfv3 1 ipv6 area 0
   !
   interface Ethernet0/1
   no ip address
   shutdown
   ipv6 enable
   ipv6 ospf 1 area 0
   !

4. Hello Chris,

   Good question, this can be confusing. Originally, OSPFv3 was created only for IPv6:

   https://tools.ietf.org/html/rfc5340

   Later, OSPFv3 was updated to support address-families:

   https://trac.tools.ietf.org/html/rfc5838

   This means you can run it for IPv6 and IPv4 (and some other address families like multicast).

   The “ipv6 ospf” commands are the “old” commands and the “ospfv3” commands are the newer commands.

   If you use “ipv6 ospf” on an interface and later use “ospfv3” then you’ll see that the “ipv6 ospf” command will disappear.

   “ipv6 router ospf” is t

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5. something which is mentioned in other lessons but is still kind of cool to see is how OSPF uses the Link Local for all the management type data its sending…

   Since I am studying for the Tshoot I am trying to lab up the majority of the topics that is covered for the exam. So I am building a ton of GNS3 labs.

   I would say that really be familiar in how IPV6 OSPF is setup for example being able to identify if something was missing from the show running configuration could be paramount to passing.

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