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Registered: ‎12-30-2017
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i *thought* i understood IPv6 Prefix Deligation... can somebody set me straight?

I have a question about IPv6 addressing on my Edge Router and the prefixes that are being handed out.

 

My ISP gives me a /56. This means that the first three and a half blocks must all be identical if my ISP is going to send traffic to _my_ edge router.

 

The second half of the 4th block is up to me to configure. AKA the sub-net ID. So I can do network 00 through ff which would be 256 unique (2^16) subnets.

 

So far, so good, right?

 

So.  If my eth0/WAN interface displays

 

2604:5100:c224::573/128

2604:5100:c224:0:dead:beef:f00d:babe/64

 

Then this would mean that my IP ranges are in the

 

2604:5100:c224:0 
through 
2604:5100:c224:ff

 

Range, right?

 

 

I have set up one interface to use prefix delegation, and the first address in the sub-net is assigned to the router.  The interface has this address:

2604:5100:c225:9501::1/64

 

My question is _why_ and _how_ ?

 

Where did 9501 come from? That seems … arbitrary?

Also, where did `c225` come from? Shouldn't it be `c224`?

 

Am I going crazy or is my edge router smarter than me?


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Emerging Member
Posts: 57
Registered: ‎03-26-2017
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Re: i *thought* i understood IPv6 Prefix Deligation... can somebody set me straight?

your router asks ISP for 2 thigs:

 

1) non-temporary association (NA or in simple words WAN side IP) for your OUTSIDE interface

2) prefix delegation (PD) for your INSIDE network.

 

WAN side IP can be given from the totally different subnet.

 

take a look at your /var/run/dhcp6c-eth0-pd.conf - you'll see 2 things you requesting (id-na and ia-pd)

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Emerging Member
Posts: 57
Registered: ‎03-26-2017
Kudos: 5
Solutions: 2

Re: i *thought* i understood IPv6 Prefix Deligation... can somebody set me straight?

your router asks ISP for 2 thigs:

 

1) non-temporary association (NA or in simple words WAN side IP) for your OUTSIDE interface

2) prefix delegation (PD) for your INSIDE network.

 

WAN side IP can be given from the totally different subnet.

 

take a look at your /var/run/dhcp6c-eth0-pd.conf - you'll see 2 things you requesting (id-na and ia-pd)

New Member
Posts: 20
Registered: ‎12-30-2017
Kudos: 2
Solutions: 1

Re: i *thought* i understood IPv6 Prefix Deligation... can somebody set me straight?

Doh!.

of course the eth0/WAN side would be a different network number from eth0/LOCAL.

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