IPv6 Address Assignment Example

This topic is to discuss the following lesson:


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Rene, just to be clear, they aren’t the same right?
2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

Hi John,

That’s right.


Subnet prefix Network engineer 2001:41f0:4060:1234::/48

shouldn’t this be /64 ?

Yes that’s right, just fixed it. Thanks!

Why are these not the same

2001:41f0:4060:10::/64 and 2001:41f0:4060:A::/64 ?

Hi Itai,

IPv6 addresses are hexadecimal so we count from 0 to F. There is no “hexadecimal 10” so be aware not to read it as a decimal 10, it’s a one and zero.

The first part (2001:41f0:4060:) is the same so let’s ignore that. Let’s look at 1 and A in binary:

1 = 0001
A = 1010

Hope this helps!


Yes, excellent - Thanks!!

Rene, reading further in this course on IPv6 address assignment it appears to me you are suggesting the above addresses are the same? - see your notes below:

In the example above I used some numbers some make sense, for example on VLAN 10 we use 2001:41f0:4060:10::/64, another good option would be 2001:41f0:4060:A::/64 since the A in hexadecimal equals 10 in decimal. For the VLANs it’s best to use a /64 so that you can use autoconfiguration for hosts.

If 10 ( 1 0 ) and A in hex are not the same or are u just suggesting you would recognize the 1,0 as 10 literally? This Topic give me headache so in my studies decided to start with it. Thanks!

When looking at an IPv6 address assignment of say for example /64. is there an assumption we should make. Reason for question is that in an example, you advised
IPv6 Global Unicast Subnet Assignments

Our customer received prefix 2001:41f0:4060::/48 and they want to use it to configure IPv6 on their entire network. Where do we start?

Then on the address assignments, we are using a /64. Do we have to have been given the information above 1st - the /48. It appears we are using 2 prefixes but only referencing the /64 at the customer end. What would be a typical test question look like given/or not given this information? looks like I need 1 on 1 :slight_smile:

Hi Itai,

It’s probably best to stick to use “A” instead of “10” as it can be confusing. It’s easy to read it as 10 while in reality it’s one, zero.

About the subnets…the ISP will give you a /48 global prefix that you can use for your network. You should use /64 subnets since it’s convenient for autoconfiguration which leaves you with 16 bits you can use to create different subnets.

A typical exam question could be something like:

“The ISP has given you global prefix 2001:41f0:4060::/48. You have five VLANs that require connectivity. What subnets will you use? Also, for each subnet what IPv6 address will you assign to your default gateway?”


You are he greatest Rene and thank you for taking your time. Be blessed and rewarded always!

Is this the correct answer for the questions regarding: The ISP has given you global prefix 2001:41f0:4060::/48. You have five VLANs that require connectivity. What subnets will you use? Also, for each subnet what IPv6 address will you assign to your default gateway?”

Network ID

Default Gateway

Hi Jeeva,

This looks valid yes. For the subnet you can use anything between 0000 - FFFF in the 4th hextet.

For the default gateway, it might be easier to use ::1 everywhere (first address in the subnet).


Thank you.

Hi Rene,
Very helpful and clearly explained.
Thank u

Hi Rene,

With reference to the example in your notes, after 2001:41f0:4060:0014::/64 will the subnets go till 2001:41f0:4060:001F::/64 and the next would be 2001:41f0:4060:0020::/64 ? Is this correct?

Thank you.

Hello Srikanth.

The network addresses of the series of subnets starting with 2001:41f0:4060:0014::/64 will follow the following sequence:


So yes, you are exactly correct.

I hope this has been helpful!


hello , do we need any licenses to do ipv6 IP assignment and other IPv6 configurations on a cisco router???

Some (older) routers require a feature set for IPv6 yes. You can look them up in the feature navigator.