How to Configure IPv6 on Cisco Routers

We know that the devices on a network require a unique identification number called IP address. We have been using the IPv4 addressing scheme for a long time. But the addresses provided by the IPv4 addressing scheme are not sufficient as the demand of the Internet is increasing day-by-day. Hence, we require an addressing scheme that can provide more IP addresses along with the security features. Internet Protocol version 6 (IPv6) comes as a solution for this.

The IPv6 addressing scheme is an upgraded version of the IPv4 addressing scheme. It provides more IP addresses in comparison to the IPv4 addressing scheme. In the post “IPv6 Address Types and Features“, we have discussed a lot about the IPv6 addressing scheme. Please read it if you missed that one. In this post, we will discuss how to configure IPv6 on Cisco Routers.

Before configuring IPv6, let’s have a quick look of some of the key features of IPv6 address.

  • An IPv6 address is 128-bit in length.
  • An IPv6 address is divided into 8 blocks and each block contains 16 digits.
  • Colon (:) is used to separate a block from other blocks.
  • An IPv6 address is written in the hexadecimal format.
  • The types of IPv6 addresses include unicast, multicast, and anycast.
  • An IPv6 address uses the prefix ID to define the Network ID (NID).
  • An IPv6 address can be configured either through the manual method or through the autoconfigure method.

Steps to Configure IPv6 on Cisco Routers

We will use the following network topology to learn how to configure IPv6 addresses between Router1 and Router2 using the manual method. In addition, we will also learn how to configure an IPv6 address using the IPv6 Autoconfiguration feature on Router3.

  1. First, you need to create the following network topology either using Cisco Packet Tracer or GNS3 depending on your choice.Configure IPv6 on Cisco Routers
  2. Once you have prepared the preceding network topology, configure the following IPv6 address on Router1.
    • IPv6 Address: 2001:ABCD:0123:1::1/64
    • Method: Manual
    • Interface: Fa0/0
  3. To configure the preceding IPv6 address, execute the following commands on Router1.
    Router1(config)#ipv6 unicast-routing 
    Router1(config)#interface fa0/0 
    Router1(config-if)#ipv6 address 2001:1bcd:0123:1::1/64 
    Router1(config-if)#no shut 
    Router1(config-if)#exit
  4. After configuring the appropriate IPv6 address on Router1, move on to Router2 and configure the following IPv6 address.
    • IPv6 Address: 2001:ABCD:0123:2::1/64
    • Method: Manual
    • Interface: Fa0/0
  5. To configure the preceding IPv6 address, execute the following commands on Router2.
    Router2(config)#ipv6 unicast-routing 
    Router2(config)#interface fa0/0 
    Router2(config-if)#ipv6 address 2001:1bcd:0123:1::2/64 
    Router2(config-if)#no shut 
    Router2(config-if)#exit
  6. Once you have manually configured the appropriate IPv6 addresses on Router1 and Router2, execute the following command on Router2 to verify the configured IPv6 address.
Router2#show ipv6 interface brief

Manually Configure IPv6 Addresses

In the preceding figure, you can see that 2001:ABCD:123:1::1 IPv6 address is configured on the FastEthernet0/0 interface of Router2.

Configure IPv6 Using Autoconfiguration

The IPv6 Autoconfiguration feature converts the MAC address of a device, such as a router into an IPv6 address. But the length of the MAC address is 48-bit then how is it possible to generate a 128-bit IPv6 address? In order to configure an IPv6 address using the autoconfiguration feature, first, you need to define the 64-bit subnet ID. For example, we use 2002:ABCD:0123:1::/64 as a subnet ID. The second portion (interface ID) of an IPv6 address still requires the 64-bit unique value. This portion can be filled using the device’s MAC address. We know that each device has a unique 48-bit MAC address written in hexadecimal. To generate a unique 64-bit interface ID, we add a fixed block called FFFE between the MAC address. It allows us to make it a unique 64-bit EUI (Extended User Interface) address.

IPv6 Autoconfiguration Example

The following figure explains how to generate a unique IPv6 address using the IPv6 Autoconfiguration feature. Let’s assume that your MAC address is 0001.43BB.7C02.
Generate an IPv6 Address Using Autoconfigure Feature

Hope you have understood the basics of the IPv6 Autoconfiguration feature. Now, let’s configure an IPv6 address on the Fa0/1 interface of Router2. First, we will manually configure an IPv6 address on Router2 to define a subnet. Then, we will use this subnet to configure an IPv6 address on Router3 using the IPv6 Autoconfiguration feature.

  1. To manually configure an IPv6 address on Router2, execute the following commands.
    Router2(config)#ipv6 unicast-routing 
    Router2(config)#interface fa0/1 
    Router2(config-if)#ipv6 address 2002:abcd:0123:1::1/64 
    Router2(config-if)#no shut 
    Router2(config-if)#exit
  2. In the preceding commands, you have defined a subnet and configured an IPv6 address on Router2. Now, execute the following commands on Router3 to generate a unique IPv6 address using the IPv6 Autoconfiguration feature.
Router3(config)#ipv6 unicast-routing
Router3(config)#interface fa0/1
Router3(config-if)#ipv6 address autoconfig
Router3(config-if)#no shutdown
Router3(config-if)#exit
Router3(config)#exit

Verifying IPv6 Configuration

Execute the following commands to verify that a new IPv6 address is configured on Router3 automatically within the subnet you defined on the fa0/1 interface of Router2.

Router3#show ipv6 interface brief

IConfigure IPv6 using Autoconfigure Feature

In the preceding figure, you can see that a unique IPv6 address has been generated on Router3 using the IPv6 Autoconfiguration feature. Once you have configured the appropriate IPv6 addresses on each router, you can use the ping command to verify your configuration. However, you have not configured any of the IPv6 routing methods, hence, you will only be able to communicate within the same subnet.

To verify the connectivity between Router3 and Router2, type the following command on Router3.

Router3#ping 2002:abcd:123:1::1

You should be able to communicate to Router2 because its fa0/1 interface’s IPv6 address is configured within the same subnet.

Router3#ping 2001:abcd:123:1:1

You should not be able to communicate to Router1 because its fa0/0 interface’s IPv6 address is configured in the different subnet and we have not configured IPv6 routing yet.

Verifying IPv6 Connectivity

In this post, we have explained how to configure IPv6 on Cisco routers using the manual and as well the IPv6 Autoconfiguration method. Hope, you have enjoyed it. Please let me know if you have any suggestions to improve this article. We would love to hear you.

Posted in IPv6 Tagged with: , ,
2 comments on “How to Configure IPv6 on Cisco Routers
  1. Sujit Dhumal says:

    Nice one Article..

    Thanks

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