DNAT/SNAT Confusion + Network+ frustration

CertifiedMonkey

I've been using CBT nuggets n10-006 and Keith barkers cert guide to study for the N+. In his cert guide he says that SNAT is static NAT but in his nugget he says its source NAT. DNAT is dynamic NAT in his cert guide but destination NAT in his nugget. Here are the definitions he gives for each.

Static NAT: 1 to 1 mapping between private and public address. Used if you have a server that needs to be accessed by the public.

Source NAT: Translates a private IP to a public IP (selects 1 from a pool)

Dynamic NAT - Translates a private IP into a public IP from a pool of addresses.

Destination NAT- Translates a public IP to anot internal device with a private IP.

Can't destination NAT be considered as static nat and can't dynamic NAT be considered the same thing as source NAT. Reason I ask is I don't want to get a question like:

What type of NAT is used when you have an internal server (with a private IP) that must be accessed by the public.

A. Snat or b. Dnat.

Well, it could be destination nat (dnat) or static nat (snat).

I'm starting to get frustrated with net+ as authors have different POVs on terms. Other examples include SCADA, virtualization terms and 802.11a-ht/802.11g-ht

Phillies8607

If it seems confusing that's because it is lol. I"ll try to explain it but CompTIA is a little weird with their NAT terms so I could be a little off. So here goes. In this example we have an internal pool of addresses on the 10.0.0.0 network which connect to the NAT router with a pool of public IP's on the 100.0.0.0 network. Static NAT and dynamic NAT are 2 different ways you could configure your NAT router while Source NAT and Dynamic NAT are more general terms. So if we configured static NAT we'd have a 1 to 1 mapping where 10.0.0.1 always maps to 100.0.0.1 from inside the router to the outside world and from the outside world (using 100.0.0.1) back to the internal address (10.0.0.1) also we'd have a static mapping with 10.0.0.2 to 100.0.0.2 from the internal network to the outside world and vice versa.

Now, for dynamic NAT this is a little different.Static NAT is no longer configured. You can only configure your network for either static or dynamic NAT. You might only have 5 public addresses and 10 internal addresses. So when a host needs to connect to the internet it uses its private IP whatever it may be 10.0.0.7 let's say it maps to a public IP 100.0.0.3. Now once all 5 public IP's are in use and a 6th host needs to connect to the internet, he'll have to wait until one of the public IP's is no longer in use.

In this example, we'll say that network with 10.0.0.0 had host A connecting to Router A (100.0.0.0). And now there is another network host A and Router are connecting to (Router B and host . Router B has public IP 200.0.0.1 and host B has internal IP 192.168.1.1. From host A's point of view he is the source NAT device connecting to the destination NAT device on the other side (host . But from hosts B's point of view, he is the source NAT device connecting to host A who is the destination NAT device.

So to recap, source NAT and dynamic NAT are how you configure the NAT router and source and destination NAT are how you would describe the hosts that are connecting to each other in this example. Also I believe destination NAT wold be how you would describe port forwarding since it is set up to have data forwarded to that destinated address. HTH!

Phillies8607

edit* I meant Static NAT and dynamic NAT are 2 different ways you could configure your NAT router while Source NAT and Destination NAT are more general terms