Hi all,

Am upgrading to a leased line form NTL. The engineer is configuring the routers and suggested that we change our current internal IP range from 192.x.x.x to something like 10.x.x.x. When I asked why he said that the 192.x.x.x range is accessable over the internet whereas the other ranges are not. This has confused me, I thought it did not really matter whatt range your internal network was as long as it was sufficiently protected from the outside.

Any input would be a great help!

Nell

192.168.xxx.xxx is reserved for private networks.  See http://www.faqs.org/rfcs/rfc1918.html

The RFC specifies 3 address ranges for private networks that are not routable across the Internet.  One Class A network, 16 Class B networks and 255 Class C networks.  They are:

10.xxx.xxx.xxx    - Class A
172.16-31.xxx.xxx - Class B
192.168.xxx.xxx   - Class C

All of these network address classes have to use either Network Address Translation (NAT) or must be tunneled in another protocol using routable address (like a VPN) to transit the Internet.

pansophic

Many thanks for the reply guys!

Cleared alot up!

Nell1

Wow! The NTL engineer is an idiot!

Chris.

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Chris A.C, CCNA, CCSA
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Technically speaking there is nothing stopping you using any private address scheme you want - if you are using a router with firewall and using NAT then there is nogreater risk of using a non RFC specified address range for private use.

Personally I would always stick to RFC defined private ranges but it isn't essential in a networked environment where NAT is used. Obviously you can't just directly assign any public address you feel like using to a machine that is directly connected to the internet (eg with a DSL modem, not using a router).

Systems Administrator
BSc Network Computing, CCNA. Both in training! :)