Config Lab: IPv6 Static Routes 1

Wendell Odom
By Wendell Odom September 28, 2021 13:05

Ever get tired of sifting through the details of seemingly random IPv6 addresses? Well, today’s lab gives you yet another quick config exercise while using very easy-to-remember IPv6 addresses and prefixes. The task today: configuring static IPv6 routes. All the IPv6 addresses and subnets are purposefully short (when abbreviated). Enjoy!

All about Config Labs

The blog has a series of lab exercises called “Config Labs.” Each lab presents a topology with the relevant initial configuration for each device. The lab also lists new requirements, after which you should create the additional configuration to meet those requirements. You can do the lab on paper, in a text editor, or use software tools like Cisco Packet Tracer or Cisco Modeling Labs.

Once you have created your answer, you can click various tabs at the bottom of this post to see the lab answers, comments about the lab, and other helpful information.

The Lab Exercise

Requirements

The network shown in the figure uses IPv6. However, it will not use a routing protocol at all. This lab begins with all the IPv6 addresses configured. Your job: add static IPv6 routes so that each device can ping each other. The specific rules for this lab are:

  • None of the routers use a dynamic routing protocol
  • Configure your static routes to use global unicast addresses as next-hop addresses, rather than link local addresses.
  • Assumptions:
    • All router interfaces shown in the lab are up, working
    • All routers and hosts have correct IPv6 addresses assigned
    • All routers have IPv6 routing enabled

Figure 1: Simple Hub and Spoke Topology

 

Initial Configuration

Examples 1, 2, 3 and 4 show the beginning configuration state of Core, Branch1, Branch2 and Branch3.

 

Example 1: Core Config

 

Example 2: Branch1 Config

 

Example 3: Branch2 Config

 

Example 4: Branch3 Config

Answer Options - Click Tabs to Reveal

You can learn a lot and strengthen real learning of the topics by creating the configuration – even without a router or switch CLI. In fact, these labs were originally built to be used solely as a paper exercise!

To answer, just think about the lab. Refer to your primary learning material for CCNA, your notes, and create the configuration on paper or in a text editor. Then check your answer versus the answer post, which is linked at the bottom of the lab, just above the comments section.

You can also implement the lab using the Cisco Packet Tracer network simulator. With this option, you use Cisco’s free Packet Tracer simulator. You open a file that begins with the initial configuration already loaded. Then you implement your configuration and test to determine if it met the requirements of the lab.

(Use this link for more information about Cisco Packet Tracer.)

Use this workflow to do the labs in Cisco Packet Tracer:

  1. Download the .pkt file linked below.
  2. Open the .pkt file, creating a working lab with the same topology and interfaces as the lab exercise.
  3. Add your planned configuration to the lab.
  4. Test the configuration using some of the suggestions below.

Download this lab’s Packet Tracer File

You can also implement the lab using Cisco Modeling Labs – Personal (CML-P). CML-P (or simply CML) replaced Cisco Virtual Internet Routing Lab (VIRL) software in 2020, in effect serving as VIRL Version 2.

If you prefer to use CML, use a similar workflow as you would use if using Cisco Packet Tracer, as follows:

  1. Download the CML file (filetype .yaml) linked below.
  2. Import the lab’s CML file into CML and then start the lab.
  3. Compare the lab topology and interface IDs to this lab, as they may differ (more detail below).
  4. Add your planned configuration to the lab.
  5. Test the configuration using some of the suggestions below.

Download this lab’s CML file!

 

Network Device Info:

The interfaces used in the lab exercise match the interfaces used in CML.

The switch used in the lab is a Cisco IOS layer 2 switch. Note that if you happen to have a layer 3 switch, to use the initial configurations as shown in this lab, issue to no ip routing command on the switch. This command will disable the routing of IPv4 packets, making the layer 3 switch act only as a layer 2 switch.

Lab Answers Below: Spoiler Alert

Lab Answers: Configuration (Click Tab to Reveal)

Answers

Figure 1: Simple Hub and Spoke Topology

Example 1: Core Config

 

Example 2: Branch1 Config

 

Example 3: Branch2 Config

 

Example 4: Branch3 Config

Commentary, Issues, and Verification Tips (Click Tabs to Reveal)

Commentary

When configuring static routes, it is important to ensure that you have all of the correct IPv6 subnet information, just a little difference in subnet mask can make a big difference in routing behavior.

For this lab you were tasked with configuring static routes to all remote subnets on all routers. The figure shows six different subnets. The Core router connects to three subnets, so it will need three static routes. Each branch router connects to two subnets, so each branch router will need static routes for four different subnets.

For Core, the three remote LAN subnets are 2000::/64,2001::/64 and 2002::/64. Just to help us get our bearings, Table 1 lists the three destination subnets, with router Core’s outgoing interface and next-hop global unicast address:

Destination Subnet Off of Router… Core’s Outgoing interface Core’s Next-Hop Address
2000::/64 Branch1 G0/1 3000::2
2001::/64 Branch2 G0/2 3001::2
2002::/64 Branch3 G0/0 3002::2

Table 1: Data to Use in Router Core’s Static IPv6 Routes

 

The configuration, shown in Example 1, repeats the ipv6 route command three times. Each time it lists the destination subnet per the first column of the table, and the next hop address per the last column. For example, the complete command to configure one static route would be ipv6 route 2000::/64 3000::2.

For Branch1, before thinking about the configuration command, think about the topology in the figure. Branch1 has two connected subnets. Then, to send packets to the other four subnets, router Branch1 will always send the packets out its G0/1 interface to the Core router next. As a result, and as seen in Example 2, all four of Branch1’s routes list 3000::1 as the next hop address. The four commands each list a different destination subnet: 3001::/64, 2001::/64, 3002::/64 and 2002::/64.

Branch2 uses the same basic logic as router Branch1. Branch2 has two connected subnets, four remote subnets, and all four static routes for the remote subnets points to router Core next. In Branch2’s case, the next-hop address of the Core router is 3001::1. As seen in Example 3, the four ipv6 route commands list 3001::1 as the next-hop address, with subnets 3000::/64, 2000::/64, 3002::/64 and 2002::/64 in the four different commands.

As you probably guess by now, Branch3 uses the same basic logic as routers Branch1 and Branch2. Branch3 has two connected subnets, four remote subnets, and all four static routes for the remote subnets points to router Core next. In Branch3’s case, the next-hop address of the Core router is 3002::1. As seen in Example 4, the four ipv6 route commands list 3002::1 as the next-hop address, with subnets 3000::/64, 2000::/64, 3001::/64 and 2001::/64.

Known Issues in this Lab

This section of each Config Lab Answers post hopes to help with those issues by listing any known issues with Packet Tracer related to this lab. In this case, the issues are:

# Summary Detail
1 None No known issues related to this lab.

 

Why Would Cisco Packet Tracer Have Issues?

(Note: The below text is the same in every Config Lab.)

Cisco Packet Tracer (CPT) simulates Cisco routers and switches. However, CPT does not run the same software that runs in real Cisco routers and switches. Instead, developers wrote CPT to predict the output a real router or switch would display given the same topology and configuration – but without performing all the same tasks, an actual device has to do. On a positive note, CPT requires far less CPU and RAM than a lab full of devices so that you can run CPT on your computer as an app. In addition, simulators like CPT help you learn about the Cisco router/switch user interface – the Command Line Interface (CLI) – without having to own real devices.

CPT can have issues compared to real devices because CPT does not run the same software as Cisco devices. CPT does not support all commands or parameters of a command. CPT may supply output from a command that differs in some ways from what an actual device would give. Those differences can be a problem for anyone learning networking technology because you may not have experience with that technology on real gear – so you may not notice the differences. So this section lists differences and issues that we have seen when using CPT to do this lab.

Beyond comparing your answers to this lab’s Answers post, you can test in Cisco Packet Tracer (CPT) or Cisco Modeling Labs (CML). In fact, you can and should explore the lab once configured. For this lab, once you have completed the configuration, try these verification steps. 

 

  1. Connect to the command line of each of the PCs and attempt to ping the other PCs. If each of the static routes was configured correctly everyone should have connectivity to each other.
  2. Also try the traceroute6 command on each PC, referencing another PC’s address, to see the various next-hop IPv6 addresses.

More Labs with Related Content!

Config Lab: IPv6 Global Unicast Addressing 1
Config Lab: IPv6 Static Routes 2
Wendell Odom
By Wendell Odom September 28, 2021 13:05
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2 Comments

  1. Raed March 1, 15:40

    Hello Wendell

    I try to use defualt route on all branch routers consider they have one Ethernet WAN link ,
    but it dose not work the , PCs at branches can not reach each other
    I use packet tracer V8

    thank you

    Reply to this comment
    • certskills March 4, 08:59

      Hi Raed,
      Interesting. Sometimes w/ static route labs I didn’t write them so that pings would work at the end of the lab, so I wondered if that was the case with this lab. But I re-read the lab, and it looks like all the routes are there in the answer so that pings should work.
      So, I implemented the lab in PT (V 8.0), and a ping from PC1 to PC2 and PC3 work for me. I assume that’s what you mean by “can not reach each other”.
      So, from PC1:
      ping 2001::100
      and
      ping 2002::100
      work.

      Try tracert instead, and let me know what those show. That’s a great command to troubleshoot routing issues. Here’s what I see from PC1:

      C:\>tracert 2001::100

      Tracing route to 2001::100 over a maximum of 30 hops:

      1 0 ms 0 ms 0 ms 2000::1
      2 0 ms 0 ms 0 ms 3000::1
      3 0 ms 0 ms 0 ms 3001::2
      4 0 ms 0 ms 0 ms 2001::100

      Trace complete.

      C:\>tracert 2002::100

      Tracing route to 2002::100 over a maximum of 30 hops:

      1 0 ms 0 ms 0 ms 2000::1
      2 0 ms 0 ms 0 ms 3000::1
      3 0 ms 0 ms 0 ms 3002::2
      4 0 ms 0 ms 0 ms 2002::100

      Trace complete.

      C:\>

      Reply to this comment
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