IPv6 Special Addresses 2

By certskills August 22, 2016 09:05

This latest config lab takes a backwards approach to configuration. In this case, it starts with a bunch of show commands, and asks you to derive some of the key configuration items on several routers. The theme: IPv6 addressing. By doing this lab, you will need to think hard about the unicast and multicast addresses listed in the output of the show ipv6 interface command.


This lab begins with a partially-complete configuration. It has some IPv6 configuration, but it is missing some. Your job is as follows:

  • Predict what the current IPv6 configuration of each router is based on the show command output listed in Examples 1 through 6.

For this lab, you can make these assumptions:

  • All router interfaces shown in the lab are up and working.
  • IPv6 routing (ipv6 unicast-routing) is enabled
  • The figure shows the planned IPv6 subnets, with plans to use OSPF process 10 on all routers and area 0 throughout the design. However, some of those features may not as of yet be configured.

Figure 1 shows the topology. Examples 1 through 6 then list the output of the show ipv6 interface command on the routers for various interfaces. Finally, Examples 7, 8, and 9 show some of the initial configuration on the three routers.

Figure 1: Three Router Topology


Example 1: R1 Gi0/1 interface


Example 2: R1 Gi0/2 subinterfaces


Example 3: R2 Gi0/1 Interfaces


Example 4: R2 Gi0/2 Interface


Example 5: R3 Gi0/1 Interface


Example 6: R3 Gi0/2 Interface


Initial Configuration

Examples 7, 8, and 9 show the beginning configuration state of R1, R2, and R3.

Example 7: R1 Config


Example 8: R2 Config


Example 9: R3 Config


Answer on Paper, or Maybe Test in Lab

Next, write your answer on paper. Or if you have some real gear, or other tools, configure the lab with those tools.

For this lab, you need to play detective. If you do build this in lab, experimenting can help a lot. So, build the topology, and add the initial configuration. Then add just one IPv6 interface subcommand, and issue a show ipv6 interface command and look for the notes about unicast and multicast addresses. Keep doing that until you get a sense for which commands make which unicast and which multicast addresses begin to show up in the output.


Do this Lab with Cisco’s VIRL

You can do these labs on paper and still get a lot out of the lab. As an extra help, we have added files for the Virtual Internet Routing Lab (VIRL) software as well. The .VIRL file found here is a file that when used with VIRL will load a lab topology similar to this lab’s topology, with the initial configuration shown in the lab as well. This section lists any differences between the lab exercise and the .VIRL file’s topology and configuration.

Download this lab’s VIRL file!

All interfaces in topology match the lab figure.

Answers: IPv6 Static Routes 3
SNMPv3 1
By certskills August 22, 2016 09:05
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  1. Ruben December 27, 17:21

    Hello again Wendell!
    A little side question that came into my mind when thinking about this exercise. Please bear in mind that I’m still only at chapter 30 of your 100-105 book, so I have no idea if this explained ahead, but here goes:

    I noticed that both sub-interfaces on R1 (G0/2.1 and G0/2.2) have the same link-local address.
    Since link-local is used by NDP, DHCP, Routing protocols and whatnot, with both being the same address, how does the router know that a specific trafic is meant to either of those VLANs, or how does he know from which VLAN the NDP/routing_protocol_trafic came from?

    I’m having trouble expressing my thoughts into a fully clear question, but hopefully you will try to help me out! Again, sorry to go a little bit offtopic!

    Reply to this comment
    • CCENTSkills December 29, 14:42

      Hi Ruben,
      Huh. I commented on your comment yesterday, and it didn’t show up. Hmmm….
      Link Local IPv6 addresses are used on a single link only. As a result, they have meaning only in the context of the link.
      So, another way to think (which might help in this case) is:
      A link local address, alone, does not identify a link nor identify a router’s interface connected to the link.
      Keeping that last bit in mind, consider the case of a single router that uses the same link local IPv6 address value on multiple interfaces. Everything the router does with that address is done “with that address… on that interface”. So the logic used when processing received frames destined to the receiving device’s link local address is filtered with “is this packet destined to my link local address on this interface”.
      Hope this helps,

      Reply to this comment
      • Ruben December 30, 08:33

        Yes, it does help with getting that mechanic in my head, however we were going offtopic, but I thank you none the less for your help!

        Reply to this comment
  2. Bav March 23, 12:32

    Great question. The bits I forgot to add were the area 0 command for OSPF and also setting the encapsulation dot1q vlan command on the subinterface – I put them on the interface. Doh!

    I’m taking the 2 exam approach, so haven’t yet covered OSPF properly.

    Reply to this comment
  3. Willis November 7, 18:31

    Hi Guys,

    I am new to CCENT/CCNA. I want to know how to open Virl file in Cisco Packet tracer so that I can do some labs.

    Much appreciated!

    Reply to this comment
    • CCENTSkills November 12, 10:56

      Hi Willis,
      You can’t open a VIRL file in PT. You would need to use VIRL to open the VIRL file. But if you don’t mind doing a little work, you could:
      – use PT to build an identical or near-identical topology
      – open the VIRL file with a text editor
      – look in the VIRL file to find the configuration of each device. It’s really obvious. You can even copy each device’s configuration out into separate files, and use those as initial configuration for your PT devices.
      – note that you may have to use different interface IDs in PT, so you’d want to change those.

      Hope this helps…

      Reply to this comment
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