MicroNugget: What is a Solicited Nodes Multicast Group in IPv6?

In this video, Keith Barker covers solicited node multicast groups, what they are, how they're created and how they can be used in a network. IPv6 and IPv4 networks act differently, and solicited node multicast groups sit at the heart of IPv6's improved speed and efficiency.

A device on a network doesn't know, by default, the Layer 2 address of its gateway. In IPv4, an ARP request would get broadcast, and the device could glean the Layer 2 address from the response that came back. But in IPv6, there's no ARP, and there's no Layer 2 broadcast.

But IPv6 does have solicited node multicast groups, so a device can send a request to that group, and if the router is configured properly and listening, it'll respond with the Layer 2 address. Learn what it takes for a device on an IPv6 network to join these special multicast groups and other ways that using them can improve your network performance.

Start learning with CBT Nuggets:

[umershakil]

Love the way he explains in every video, never getting bored.

[tedvarias]

Keith Barker has a teaching gift. His explanations are clear and his delivery is engaging. I wish my college professors were this good.

[matthewcardinal]

What I enjoy the most about Keith is that you can hear that he is excited to teach others and he is enjoying what he is doing. Thank you Keith!!!

[KeithBarker]

Thanks for the feedback. I appreciate it.

Best wishes,

Keith

[NoTySir]

Keith you're the man! This was super helpful for clarification.

[naveedahmedchaudhry]

Scott Morris at CBTNuggets, he needs to fix his CCIE all in one video series about IPV6, he described last 32 bits are used for SNM, I had to research and find out that only 24 bits are used. I really enjoy watching and learning from Keith Barker, massive respect for your Sir, if you're listening. God bless you!

[kimberly]

This thing just wouldn't click in my head untill I watched the video! Thanks Keith!

[alexeifarinas]

Thanks, very clear explanation and very positive teaching attitude!

[poochey]

Why does PC1 not just send the packet direct to the L3 R1:G2/0 IPv6 Address configured as its default gateway? 
And isn't the whole point of an ARP request/Neighbor Discovery Protocol to obtain the L2 address of the destination?
Won't it just have a L2 broadcast MAC when sending the Solicited Nodes Multicast anyway so it will be delivered to all the devices on that layer 2 segment? 
I think this example would be better with more layer 2 information. I'm just as confused as i was before i watched it...

[lean.rp_]

It helped me a lot to understand. Thanks you man!

[MrVecheater]

This helped me a lot
Your explanation is well structured and I don't need to watch some kind of previous video to understand it. Just like Tech quckie

Maybe in a live presentation you should speak a tiny bit more slowly than here but it's perfectly fine for a video

[lohphat]

But how are multicast group members enumerated and who decides who is a valid member to receive packets for that group? Is it the router? All routers? The switches? Otherwise is it the client who decides which group traffic to listen to?

It's unclear where the group memberships are "brokered" and who permits joining.

[marcosvita]

It helped me a lot! Thanks for this explanation.

[digitaldistancerecords]

So this means the router is going to join that multicast group to, so it can send a message to that group so the PC can see if there was an request for the router's mac address?

[ar-tsji]

But if the PC already knows it's gateway's IP address, why not just send the request to find the mac to that address instead of the solicited-node multicast address? Am I missing something? I understand how this all works just wondering if there is something I am not understanding here.

[emanuelsantos]

This is very helpful. Thank you so much!

[whomptalosis]

How does PC1 get R1s Solicited Node Multicast address without knowing its MAC address?

[MrEnterainment]

Very good explanation, thank you very much for this :)

[loztagain]

something I'm confused about is how this works with privacy extensions. Is the multicast L3 IPv6 packet, also sent to a multicast L2 ethernet address for instance? And, if so, am I to assume that the corresponding device has made a corresponding mac address to its randomly generated IPv6 privacy address?

[tango]

Keith why is the link local address not 128 bits why so short?