From: Bob Sinclair (bob@bobsinclair.net)
Date: Tue Dec 20 2005 - 18:31:05 GMT-3
YUP! IPv6 provides PLENTY of address space. The 128 bits can be broken down
many ways, but a lot of the benefits of IPv6 autoconfiguration are built
around the EUI-64 address. This is the MAC address with 16 bits of padding.
Using EUI-64 addressing the router can supply the subnet and the host can
auto-configure the host portion. Basic idea would be 48 bits from ISP, 16
bits for enterprise subnetting, and 64 bits for host address.
So, the benefit of the /64 is not that you can have 2 to the 64th addresses in
a subnet, but auto-configuration.
Hope that helps,
Bob Sinclair
CCIE #10427, CCSI 30427
www.netmasterclass.net
----- Original Message -----
From: CCIEin2006
To: lab
Sent: Tuesday, December 20, 2005 3:45 PM
Subject: IPv6 Address Allocation Excessive?
According to the Cisco Press book "Implementing Cisco IPv6 Networks", RIR's
allocate /32 prefixes to ISP's. ISP's allocate /48 prefixes to each
customer
site. Each customer site uses /64 prefixes for each subnet.
Isn't that a little excessive?
Why does every subnet need a /64?!? Isn't that 1.8 quintillion addresses
per
subnet?!? What a waste!
On the other hand If the average ISP has a /32 and he is allocating /48
that
means he only has 2^16 or 65536 prefixes to allocate. Doesn't seem that
much
at all.
I know IPv6 is supposed to provide plenty of addresses, but aren't these
large allocations reminiscent of the 1980's when IPv4 registries were
handing out Class A and Class B subnets to every Tom, Dick and Harry that
asked for one?
What I'm saying is that even though the IPv6 address space can accommodate
3.4*10^38 addresses, if the registries keep handing out such large chunks
of
address most of the addresses will be wasted.
I'm just concerned that in the future there won't be any addresses left to
assign to my wireless electric toothbrush!
Any thoughts?
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