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Re: classful routes redux

  • From: Stephen J. Wilcox
  • Date: Wed Nov 02 19:59:38 2005

On Wed, 2 Nov 2005, Fred Baker wrote:

> A class A gives you 16 bits to enumerate 8 bit subnets. If you start  
> from the premise that all subnets are 8 bits (dubious, but I have  
> heard it asserted) in IPv4, 

not according to my view of the internet.. 
 
/8: 18 /9: 5 /10: 8 /11: 17 /12: 79 /13: 179 /14: 335 /15: 651 /16: 8553 
/17: 2855 /18: 4793 /19: 10791 /20: 11877 /21: 9990 /22: 13168 /23: 14299 
/24: 93293

> and that all subnets in IPv6 are 16 bits > (again dubious, given the recent
> suggestion of a /56 allocation to an edge network), a /48 is the counterpart
> of a class A. We just have a lot more of them.

well, /56 /48 /32 seem to have resonance but are not special in any way

> All of which seems a little twisted to me. 

you think? :)

> While I think /32, /48, / 56, and /64 are reasonable prefix lengths for what
> they are proposed for, I have this feeling of early fossilization when it
> doesn't necessarily make sense.

classes are bad. but recognise v6 is a bit different, /48 or /56 is the per site 
bit which is not comparable to v4. then /32 is is largest generally accepted 
prefix for bgp. this suggests anything can happen from 0-32 in bgp and anything 
can happen in provider igp for 32-48 or 32-56 and again anything in end user igp 
for 48/56-128

repeat 3 times, twice daily. classes are bad, v6 is not v4

Steve





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