Address Allocation Q

It does not mean anything.

Class B addresses always use the first 16 bits for the network portion, and the remaining 16 bits may be allocated in any desired fashion for

The /27 notation is for Variable Length Subnet Masks (VLSM), which superceeds the Class structure. /27 indicates that at the address aggregation point, the first 27 bits are used to determine the network portion for routing purposes, and the remaining 5 bits are for internal routing purposes.

Ignorance or politics. Either the person who made the request did not know that the / numbering format replaces the class system, or else the person does know about routing and how a /27 would work technically, but wants the address to be in the 128.*.*.* to

An example of non-routing reasons: I did not check your posting headers to see where you posted from, but I notice that your email address appears to be Chinese. Most of China's well-known IPs start with somewhere near 200.*.*.* to 205.*.*.* -- addresses that fall into "Class C" under the old classification system. ISPs in China developed quite a bad reputation for permitting spam and of not bothering to respond to abuse reports of any kind; and the owners of many address blocks in that range simply could not be found (no-one would take responsibility for the ranges.) As a result, addresses in 200.*.*.* to 205.*.*.* appear on many formal and informal black-lists, and there are a lot of places that will simply not accept any packets from addresses in that range. The addresses in China in the 128.*.*.* to 191.*.*.* range were, generally speaking, better managed, and are less likely to be blocked. Thus, a request for a /27 allocation out of a Class B block could be a request for 32 IPs somewhere in the IP ranges that have a better reputation.