question about bogon prefix

[Song Li <refresh.lsong () gmail com>]

Hi everyone,

I found many ISP announced bogon prefix, for example:

OriginAS Announcement Description
AS7018  172.116.0.0/24  unallocated
AS209   209.193.112.0/20 unallocated

my question is why the tier1 and other ISP announce these unallocated 
bogon prefixes, and another interesting question is:

If I am ISP, can I announce the same bogon prefix(172.116.0.0/24) with 
AS7018 announced? Will this result in prefix hijacking?

Thanks!

--
Song Li
Room 4-204, FIT Building,
Network Security,
Department of Electronic Engineering,
Tsinghua University, Beijing 100084, China
Tel:( +86) 010-62446440
E-mail: refresh.lsong () gmail com