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DEMO: SLAAC

Enabling IPv6 unicast routing on a Cisco Layer 3 switch activates SLAAC, allowing connected devices to automatically generate their own IPv6 addresses from router advertisements. This configuration also provides default gateway assignment across all VLANs through the switch's link-local address.

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About this video

Stateless Address Autoconfiguration (SLAAC) for IPv6 is activated on a Cisco Layer 3 switch by entering the ipv6 unicast-routing command in global configuration mode. Because the switch serves as the default gateway for all VLANs on the network, enabling this single command causes it to immediately begin sending router advertisements to every connected segment, effectively extending IPv6 routing capability across the entire infrastructure at once. Once router advertisements are transmitted, client devices process the network prefix information they contain and autonomously construct their own global unicast IPv6 addresses by appending self-generated host bits. This can be verified on a Windows client using ipconfig, which will display both any statically assigned IPv6 addresses and the newly autoconfigured address derived from the router advertisement. The switch's link-local address is also automatically recognized and populated as the IPv6 default gateway on client devices, requiring no additional manual configuration. The end result is a fully functional IPv6 environment across all VLANs, where clients can route traffic to other network segments using their autoconfigured addresses and the switch's link-local address as the gateway. Connectivity can be confirmed by pinging IPv6 addresses on other VLANs from a client device, validating that inter-VLAN IPv6 routing is operating correctly through the Layer 3 switch.

What you'll learn

What's covered

Enabling IPv6 Routing on Switch

Aligned to

Cisco CCNA
1.8 Configure and verify IPv6 addressing and prefix
1.9 Describe IPv6 address types
1.10 Verify IP parameters for Client OS
3.3 Configure and verify IPv4 and IPv6 static routing

Key terms

Virtual LAN
VLAN
A logical grouping of network devices that behave as if they are on the same network regardless of physical location.
Default Gateway
The router that a device uses to send traffic to destinations outside its local network.
Layer 3
The Network layer of the OSI model, responsible for logical addressing and routing packets between networks.
IPv6 Unicast Routing
A Cisco IOS command configuration that enables a router to forward IPv6 unicast packets between interfaces.
Stateless Address Autoconfiguration
SLAAC
An IPv6 mechanism that allows devices to automatically generate a globally unique IPv6 address using the network prefix from a Router Advertisement combined with a locally generated interface identifier, without requiring a DHCP server. SLAAC uses the EUI-64 process or a random interface ID to create the host portion of the address.
Router Advertisement
RA
An ICMPv6 message periodically broadcast by IPv6-enabled routers to announce their presence, advertise network prefixes, and provide default gateway information for SLAAC. Hosts also request RAs immediately on startup by sending a Router Solicitation.

Topics

Ipv6 Slaac Router Advertisements Cisco Ios Layer 3 Switching Vlan Configuration Networking

Transcript

Turning SLAAC On

To turn SLAAC on, I have chosen to do this on switch one. That's my layer 3 switch that's on my network, and so it is the default gateway for all my VLANs.

I'm on my switch one. I'm going to get into global configuration mode and use the command ipv6 unicast-routing and hit enter. That's it, it's turned on. Now this device is starting to send out router advertisements for the rest of the devices on the network.

Checking the Switch

Let's take a look at some of the IPv6 addresses that are associated with it now. What I'm going to do is get out of my global configuration mode and take a look at show ipv6 interface, and I want VLAN 10, so that's the one that we'll take a look at.

You can see now that it's got the global unicast address, the GUA. This is the one that we assigned it, so that's not a surprise at all. But it's joined now to the all nodes group — it was joined before, actually, to the all nodes group — and it's joined to this router group now, so it can send out or receive these router solicitations. So it's joined that, and then it's got some other networks that it is joined on as well.

Checking the Client

Now let's take a look at the client side. I'm going to open up a command prompt on my demo laptop and type in ipconfig. With ipconfig we can see it has gotten some additional information here. This is the network that we're talking about, and on here we can see that it's got the statically assigned address that was on here, and it also has a new address here.

What's happened is it has taken the router advertisement network that it received and then generated its own host bits on here. So we can see that it's already receiving the information in the RA and generating. Now I have this set up where it's already receiving these router advertisements and then creating its own IPv6 address on this network.

The last thing to note about this is the default gateway here, FE80::219 and the rest of this right here. We can also see that that is one of the addresses here on the switch, so that lines up as well, that it now has the default gateway in here for that device right there, so I can send traffic in that direction. So that exists on here as well.

The last thing we can also check is, I can bring up another command prompt and see if now I can ping one of the pies in another VLAN using IPv6. I'll hit that, and sure enough, I can now ping IPv6 addresses in other networks as well.

So there you have it. We have now set up SLAAC on our networks and it's affecting all of our VLANs at this point in time. They're all getting default gateways.

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