Ipv6 delegation/track interface explanation?

[dopey]

Can someone either provide me with an short primer on how ipv6 prefix delegation works, or provide me with a pointer to a good explanation of it?

Also, what exactly does track interface do in the LAN ipv6 configuration?

[dopey]

Perhaps i can explain what it is I'm running into as well to see if people have any ideas.

i'm using comcast business class, and the comcast router (I have a /29 static ipv4 block) is configure to request a /56 from comcast.

If I have pfsense request a /64, my WAN gets a /64:
inet6 xxx prefixlen 64 autoconf

And the LAN interface is tracking the WAn interface and it gets:
inet6 xxx prefixlen 60
a 60, so the local lan clients can't autoconfigure an IP address.

If I set the prefix delegation size to /60, everything works, both WAN and LAN get a /64 and all is good.

I really can't wrap my head around why this would be.

[hda]

@dopey:

…
If I set the prefix delegation size to /60, everything works, both WAN and LAN get a /64 and all is good.

I really can't wrap my head around why this would be.

A prefix /60 gives you a collection of 2^4-1 subnets for your site. Each LAN, WAN node has its own unique subnet value, and such address has mask /64 …

[dopey]

@hda:

A prefix /60 gives you a collection of 2^4-1 subnets for your site. Each LAN, WAN node has its own unique subnet value, and such address has mask /64 …

Thanks for confirming that.  That's what i had guessed was occurring. 
But how would something like this work of the ISP does'nt provide you a /56.  For example, if their router only requested a /60, how would one allocate IPv6 addresses to WAN/LAN?

Also, why is this occurring when I try to request a /64:
And the LAN interface is tracking the WAn interface and it gets:
  inet6 xxx prefixlen 60

Where is the LAN interface getting this /60?

Thanks.