MicroNugget: What is IPv6 PreFix Delegation?

In this video, Keith Barker covers why IPv6 Prefix Delegation is useful. In addition to assigning individual IP addresses, ISPs can assign entire networks to customers. He’ll walk through all of the steps to configure it effectively, as well as verify that it’s working correctly.

If an internet service provider has a customer who needs a hundred subnets, the ISP could assign them individual IP addresses, or they could choose to assign an entire network. One of the methods of delivering that information is through prefix delegation. Keith discusses the theory behind this capability, then gives an example in which prefix delegation would be useful. Once you understand the overall concept, he’ll walk through each step of configuring a range of addresses to assign to a fictional customer. By the end of the video, you should feel comfortable with not only the various applications of IPv6 prefix delegation but also how to set it up when you need it.

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[vladislavkaras]

I could not find a better video about how ISPs allocate their IPv6 and how local devices gets an actual GUA IPv6 address.
Thanks for the video!

[KeithBarker]

Hi Russdog-

The global unicast address range begins with 2000 through 3fff (inclusive). The reason for that is that the specification for the global unicast address is 2000::/3 (so there is an example of the /3).

Each of the characters in 2000 are Hex, and really represent 4 bits.

In binary, the 2000 would look like this: 0010 0000 0000 0000

The /3 means only pay attention to the first 3 bits, leaving us with 0010 (2) or 0011 (3) as the first character.

Hope that helps,

Keith

[egg]

Thanks for having such a detailed video. It helped me way more than the Cisco site's tutorials did.

[MystikIncarnate]

Thank you very much Keith, you're my hero. I love these straight forward tutorials. off to my lab to do some testing!!

[Aghabalayev]

Thanks a lot Keith. I love your lessons very much!

[KeithBarker]

Hi Russdog-

In the demonstration, I didn't use the command "address prefix 200...." to assign IP addresses for this pool to hand out, I only configure the DHCP pool for prefix delegation.

The command: "show ipv6 local pool" should show the network block from which PD is occuring.

If you follow the example in the video, and do the show command at about the 4 minute mark, are you getting different results than shown in the video?

Keith

[aamirsadiq]

HI Keith, i wish you could demo how to add a DHCPv6 relay agent in the same mix

[dumbledor]

This is a great video if you need to know how to setup your router at home. Thank you!

[mattwilson]

Thanks Keith, great MicroNugget. If the link between PE & CE goes down, all the global unicast addresses on all interfaces on the CE router are lost. Is this the case? How would that affect the internal network WRT routing, as all the internal IPv6 addresses would only be link-local ones which aren't routable?

[serggarcia]

Outstanding info! So, for a home network, our router configuration should have prefix delegation selected, correct?

[Russdog]

I saw a question on the ICND2 test practice that had an IPV6 address with a /3 on the end! What would that mean?

[Mi_Fa_Volare]

Your tone reminds me of LinusTechtips.

[Russdog]

When I configure the first router.. When i type Show IPV6 DHCP pool it doesnt show anything except the CUST-POOL. And no address ranges.

[BoiseTriathlete]

Hi Keith - I am working my way through your IPv6 course, and I have a bit of a PD misunderstanding.  I wanted to vary your example (to reinforce IPv6 subnetting for me).  In my implementation, I wanted R4 (the ISP) to have a /50 prefix pool which would be carved up into /61 subnets for customers (11 bits so I could have 2048 such subnets to hand out).  

When I tell R4 to use a local pool of 2001:db8:2:c::/50 61, the IOS ignores that I specified the "c" and instead shows the prefix of 2001:db8:2::/50.  If my math is right, 2001:db8:2:c::/50 is a different subnet than 2001:db8:2:0::/50.  Why is the IOS ignoring my "C"?  I am trying to set the 49th and 50th bit to be 1 in binary, hence the hex of C (but I am sure you picked up on that).

[Russdog]

When I do the "Show ipv6 local pool" I get nothing displayed

[cbtnuggets]

Could you be a little more specific? What are you having trouble with?

[vijgai]

Please slow down a bit while talking and typing. Other than that all good.

[tahersadeghi]

It looks like you are repeating to yourself rather than teaching. You talk too fast and type too fast and then say it was so easy!