CCNA Routing with IPv6

Chapter 1 – Static Routing

IPv6 is routable, just as IPv4 is. This means that static routing and dynamic routing protocols can still be used.

OSPF has even had an upgrade to support IPv6. We’ll see how that works very soon.

Let’s start by configuring a few simple static routes. These are very similar to IPv4, so it will feel familiar.

Step 1 is to enable IPv6 routing on the router. Some Cisco routers have this enabled by default, and some don’t. 

We use the ‘ipv6 route’ command, followed by the destination network, and the next-hop IP.

It’s the same idea if we want to add a host route. The only difference is that the prefix length is 128-bits.

We can easily add a default route too. In IPv6, ::/0 is the default route.

And of course, floating static routes are still available. These are backup routes that have a higher metric than any dynamic routing protocol.

We look at the routing table with ‘show ipv6 route’. Please understand that this is an entirely different routing table to IPv4. We can have both, but they’re independent of each other.

Here’s an advanced tip: We don’t strictly need to use global unicast IPs on point-to-point links. The alternative is to use link-local addresses only.

If you want to do this, don’t configure the interface with an IPv6 address. Instead, configure the interface with the ‘ipv6 enable’ command.

Unfortunately, there are drawbacks. It’s harder to monitor and troubleshoot interfaces that are configured this way.

Chapter 2 – OSPFv3

In another part of the series, we covered OSPF. That was OSPF version 2; The most popular version of OSPF.  The downside is, it’s IPv4 only.

When IPv6 was created, OSPF needed to be updated. The result was OSPF version 3, which can be used with both IPv4 and IPv6 at the same time.

Or, you could use OSPFv2 and OSPFv3 side by side if you want to.

Now, don’t panic. Nearly all of the OSPF concepts you’ve already learned still apply. There are still neighbours, areas, hello messages, timers, and so on.

In fact, OSPFv3 won’t even be heavily tested in the CCNA exam. But I feel it’s too important not to give it a good mention.

The main difference is in the configuration. The confusing part is, on a Cisco router, there are two completely different ways to configure OSPFv3.

The older method is very similar to the way you already know. We just use ‘ipv6 router ospf 10’ to start the process, and then add enable OSPF on the interfaces.

It used to be done like this when it was common to use OSPFv2 for IPv4 and OSPFv3 for IPv6.

In the newer way, Cisco added address families. Other routing protocols, like BGP, use them too.

An address family is just the protocol that we’re configuring. In our case, this is IPv4 and IPv6. Address families allow us to configure OSPF to support both versions of IP.

Let’s try out the new method of configuration. R2 is already done, so we’re going to configure R1.

This is fresh config, so we’ll need to enable ipv6 unicast-routing again.

As normal, we have to start the process and assign a process number. If we want to apply special configuration to areas, such as authentication, we can do that here. We won’t bother with that this time.

We should also change the reference bandwidth. This is measured in megabits per second.

And of course, the router-id. Notice that it’s still in IPv4 format? Remember this isn’t an IP address, it’s a 32-bit number that looks like an IP address.

In OSPFv3, we don’t use the network command anymore. Instead, we enable OSPF on interfaces.

Here, we’re adding this interface to OSPF process 10, in area 0. This will enable hello messages, and advertise the network on this interface.

Back under the OSPFv3 process, we can try out address families. ‘IPv6 unicast’ will be our address family. ‘Ipv6 multicast’ is another option. 

We’ll now advertise a default route. As this is in the ipv6 address family, it will advertise the IPv6 default route. This won’t affect IPv4 in any way.

Looking at the IPv6 routing table now, we can see the OSPF routes that R2 is advertising.

It’s likely you’ve noticed something interesting about OSPF routes…

In this lab, we have four routers in a square topology. Each router has two loopback interfaces, and two links to other routers.

You need to allocate and /127 networks to the links between routers, and /64s to the loopbacks. Then you need to configure OSPFv3 on all four routers.

That brings us to the end of our IPv6 collection of videos. In the next section, we’ll start looking at network architecture, which, in my opinion, is one of the most interesting topics.