Private IP address?

Hi,
I have a doubt on the utility of the private IP
address range 172.16/16 to 172.31/16, 192.168.0/24 to
192.168.255/16 etc.

AFAIK, these IP addresses are given to the sys admins
to assign inside their AS and these must be not
advertised to the world outside. For communication
with the outside world we must use some well defined
unique IP address. 

Is that so?

This leads to a doubt .. 

If i have a switch with say, two routers in it having
private IP addresses assigned as 172.31.1.1 and
172.31.1.2. I can then not have these IP addresses
outside in my network. Right?

regards,
mareline s.



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