Subnetting
Last updated
Last updated
Although client subnets are /64, we can allocate blocks of these /64 subnets, just like we did with IPv4. For example,
A /63 would be two /64 subnets.
Every University in Ireland has a /48. This means there are 64-48 or 16 bits for local subnetting.
ATU Letterkenny has 2^16 networks of 2^64 nodes. The 2^16 networks can then be used for hierarchical subnet planning.
On a large-scale basis, the
/12-23 for a registry
/19-32 for an ISP
/48-56 for a single site, the recommendation is /48
/64 per final subnet
The scheme works like this.
Define parts of the IP address as p1, p2 , p3, ... pN in order, so that an IP address is composed of these parts contiguously. Boundaries between each part are based on the prefix assigned by the next level authority.
Part p1 is the leftmost part probably assigned to a registry.
Part p2 can be allocated to a large internet service provider or to a national registry.
Part p3 can be allocated to a large customer or a smaller provider, etc.
Each part can be of different length. We define l(pX) the length of part X. The algorithm for allocating addresses is as follows:
For the leftmost part (p1), assign addresses using the leftmost bits first
For the rightmost part (pN), assign addresses using the rightmost bits first
For all other parts (centre parts), predefine an arbitrary boundary (prefix) and then assign addresses using the centre bits first of the part being assigned.
This algorithm grows assigned bits in such way that it keeps unassigned bits near the boundary of the parts. This means that the prefix between any two parts can be changed forward or backward, later on, up to the assigned bits.
There is no such a thing as ownership of IPv6 addresses, this concept is different from IPv4 which has;
PI space (Provider Independent)
PA space (Provider Aggregable)
Additionally, IPv6 addresses allocation is funnelled through the Local Internet Registry (LIR) as opposed to direct request from the Regional Internet Registry (RIR). Only LIR can make IPv6 allocation requests. The LIR do not have ownership rights over the ranges allocated to them.
