abhi.desai wrote:
Hi,
I am a newbie trying to understand CIDR.
from my understanding, CIDR was introduced to replace the classful networking scheme having Class A, B and C of network addresses. Does this mean that an organization can be assigned an IP network of the type 195.192.0.0/10 ?
OR
The IP network assigned to an organization can only be one of the classes eg. 195.192.0.0/24 and the CIDR is only used by the routers to group the networks to reduce the routing table ?
-abhi
If you can get a /10 out of any registrar these days you're a miracle worker. :-)
But yes - an organisation can be allocated assigned a CIDR block - my company was recently assigned a /23 when we upgraded our internet links - in fact, most NIC'd will use a /22 as a minimum "allocation" (destinct from an "assignment" range)[1] - but most big blocks are "allocated' to ISP's or carriers rather than companies - companies can only get "assignments' usually, either from their ISP if they're single-homed of the relavent NIC if they're multi-homed.
And CIDR is also used to "aggregate" routing addresses in core networks to reduce the BGP table size, but allocations or assignments are made based on CIDR, so your first question gets the "yes" answer.
Cheers.
[1] "Allocations" are made to organisations who can utilise those addresses as they please - re-asign them to clients, subnet them and assign across a lot of organisations - usually carriers. "Assignments" are only valid for the one organisation and can not be issued to anyone else by that organisation.
