"These Two devices are natted" = What does that mean?

Posted on 2013-12-18
Last Modified: 2013-12-22
What does it mean when two devices are natted?
I know that a router uses NAT to allow devices from outside the company to communicate to devices inside the company.  But I read a piece of documentation discussing two devices INSIDE of the company that are natted.  Why should two devices inside the company require NATTING?
Question by:brothertruffle880
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LVL 44

Accepted Solution

Darr247 earned 250 total points
ID: 39728310
Network Address Translation might need to occur anytime more than one subnet exists inside the company.

Even in the same computer, if Internet Connection Sharing is being used, NAT would occur between the 2 network adapters involved in the sharing.
LVL 11

Assisted Solution

Miftaul earned 250 total points
ID: 39728420
NAT is not required between the subnets if they are in private IP block RFC1318. As long as the routing is there, no NAT required.

NAT is required only when we have private IP and we want to communicate with the public internet IPs.

But in very few scenarios, NAT is done within the company subnets. Say you have a merger, your local internal subnet and the remote site internal subnet overlaps in a site to site connectivity.

eg, your office-a subnet and office-B subnet overlaps. You have to have NAT over VPN.
LVL 44

Assisted Solution

Darr247 earned 250 total points
ID: 39730511
If you work for a large company that was on the networked bandwagon early, such as HP, GM or IBM, nearly all their internal (L2) switches/routers/et al have public IPs (HP had an entire /8 public IPv4 block the last I knew), but they also have lots of different private IP subnets inside various buildings/plants where NAT'ing happens.  That's why I said, *might* need to occur.  :)
LVL 11

Assisted Solution

Miftaul earned 250 total points
ID: 39731249
I agree with you. the word *might* flipped your whole sentence to me, my mistake.

But the possibility of internal NAT is very limited now a days.

The place I am with happens to use Public block of IPs for individual devices including workstations. We also have private block of IP within the network, we hardly do NAT within LAN, rather solely use routing internally.

NAT is only done at the edge when traffic is destined for internet.

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