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TechKnowSurge Catalog Videos DEMO: Dual Stack Configuration, Router
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DEMO: Dual Stack Configuration, Router

Dual stack router configuration enables a single device to handle both IPv4 and IPv6 traffic simultaneously. This covers enabling IPv6 unicast routing, assigning IPv6 addresses to an interface, and understanding how Cisco devices automatically generate EUI-64 link-local addresses.

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About this video

Dual stack routing is a transition strategy that allows a single router to process both IPv4 and IPv6 packets without requiring a full cutover to the newer protocol. Before any IPv6 configuration can take effect, the global command ipv6 unicast-routing must be entered, which instructs the router to forward IPv6 packets between interfaces. Without this step, IPv6 addresses can be assigned but the router will not route traffic between networks. Once global IPv6 routing is enabled, an IPv6 address is assigned to an active interface using a /64 prefix length, which is the standard for most IPv6 subnets. Cisco routers automatically generate a link-local address for any interface with IPv6 enabled, and by default they use the EUI-64 method, which derives the address from the interface's 48-bit MAC address by inserting the hex value FFFE at the midpoint and flipping a specific bit. This link-local address is required for IPv6 to function on the interface and is created automatically whenever a global unicast address is configured. The EUI-64 format can also be explicitly applied to a global unicast address assignment, allowing the router to use the same MAC-based derivation for a routable address rather than a manually specified host portion. After configuration, the show ipv6 interface brief command confirms both the assigned unicast address and the auto-generated link-local address are present and active. A successful ping to another IPv6 host on the network validates that the interface is correctly configured and that the router is forwarding IPv6 traffic as expected.

What you'll learn

What's covered

Router Dual Stack Configuration

Aligned to

Cisco CCNA
1.8 Configure and verify IPv6 addressing and prefix
1.9 Describe IPv6 address types
Cisco CCST Networking
2.3 Identify IPv6 addresses and prefix formats

Key terms

IP Address
A numerical label assigned to each device connected to a network that uses the Internet Protocol.
Router
A network device that forwards data packets between networks based on IP addresses.
Media Access Control
MAC
A sublayer of the Data Link layer that controls how devices on a network gain access to a medium and transmit data.
Dynamic Host Configuration Protocol
DHCP
A network protocol that automatically assigns IP addresses and other configuration parameters to devices on a network.
Dual Stack
A network configuration that enables a device to operate with both IPv4 and IPv6 addresses simultaneously on the same interface.
IPv6 Unicast Address
An IPv6 address that identifies a single network interface, with packets delivered to that specific interface.
Extended Unique Identifier 64-bit
EUI-64
A method for automatically generating the 64-bit interface identifier portion of an IPv6 address by inserting 0xFFFE into the middle of a device's 48-bit MAC address and flipping the Universal/Local bit. EUI-64 is used by SLAAC and stateless DHCPv6 to create host-specific IPv6 addresses.
Link-Local Address
An IPv6 address in the FE80::/10 range that is automatically assigned to every IPv6-enabled interface and used only for communication within a single network link. It cannot be routed beyond the local Layer 2 segment and is required for Neighbor Discovery and router communication.
Global Unicast Address
GUA
A publicly routable IPv6 unicast address beginning with the prefix 2000::/3, equivalent in role to a public IPv4 address, used to identify a device uniquely across the internet. GUAs are assigned by ISPs and regional internet registries and are the addresses used for internet-facing communication in IPv6.
IPv6 Unicast Routing
A Cisco IOS command configuration that enables a router to forward IPv6 unicast packets between interfaces.

Topics

Dual Stack Ipv6 Eui 64 Cisco Ios Router Configuration Networking

Transcript

Checking the Current Configuration

Dual stack means that it can operate both with IPv4 addresses and IPv6 addresses. I'm on this router, and the first thing that I'm going to do is take a look at the interfaces and see if there are any configurations for IP version 6 on it at this point.

So I'm going to do a show ipv6 interface brief, to take a look at the interfaces and any association with IPv6 addresses. We can see that these are unassigned, first of all, and that two of the interfaces are administratively down, so the shutdown command is on there, and we have one interface up. It's this one interface that we're actually going to configure.

The first thing that we're going to do is take a look at the running config of this, so I'm going to do a show run interface fa00. We hit enter, and there is the configuration of this interface right there. We can see that there is no IPv6 on there.

Enabling IPv6 Routing

The first thing that we'll do is set this router up to actually route IPv6 packets. To do that I have to be in global configuration mode, so I'm going to get into global configuration mode, and the thing I'm going to type in is ipv6 unicast routing, and hit enter. That will configure this router to be able to route unicast traffic for IPv6.

Adding an IPv6 Address

The next thing that I'm going to do is attach an IPv6 address to this machine. What I can do is type in interface fa00 to get into the interface, and then I can type in ipv6 and see what commands are associated with IPv6.

I see here I can actually pick up a DHCP address if I wanted to pick up a DHCP address. If I want to enable the IPv6 interface, I just type in enable. What that will do is create a local link address, so at least it can communicate on the line. So I can just enable it. What we're going to see is that the local link address is going to automatically be created when we do these other commands, because an IPv6 port needs to have a local link address — it's part of the way IPv6 functions. We could just enable IPv6 at this point in time, but I want to show you how it will automatically add that.

We also see now that we can add an address to this. That's what we're going to do in this case right here, so let's add an address to it. The address that we're going to add is fc:1::1 — we're going to actually add a couple of zeros in there — slash 64. So it's going to be the address that we're trying to add plus the prefix length. Then we can hit enter.

The Local Link Address

Let's now take a look at show. I'll have to put the do at the front of it: do show ipv6 interface brief. I hit enter, and now we see the IPv6 address associated with fa00.

The other thing that we see here is that the local link address is added as well. We see that ffe is in the middle of this, so that should give us a clue that this is a EUI-64 address right there. So it automatically added a local link address, and for Cisco devices it added the EUI-64.

This right here is associated with the MAC address of the switch, and if I wanted to see that I could do show interfaces and take a look at the interfaces. We see that the MAC is 0026 777f 468c. So, 468c — it is the same, 468c, it's the same thing. So it's taken the MAC address to form the local link address on this, so that gives us once again a clue that this is a EUI-64. Now, by default Windows will not use EUI-64, but by default Cisco does use EUI-64.

Adding a Unicast Address with EUI-64

That's the local link address. The next thing that we'll do — let's break out of here — is let's also add a unicast address to this that uses the EUI-64. To do that I'm going to type in ip address — well, it's going to be a version 6, right? So ipv6 address, and then we'll type in our fc 1::1, it is going to be a slash 64, and we want EUI-64 in there. So we hit enter.

Now let's take a do show ipv6 interface brief. We hit enter, and now we see that it's added that EUI-64 IP address in there as well.

Testing It

So now we've configured this device to be able to route IPv6 addresses, and we've also configured one of the ports to have IPv6 addresses on it. If I wanted to test it out, the other thing I could do is a ping, and I can ping another device on this network to test it out. So let's do 1::, let's try pinging 3 — and it's successful.

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