Join Greg Sowell for an in-depth discussion in this video Network Address Translation (NAT), part of Foundations of Networking: Network Media (WANs).
- [Voiceover] Network Address Translation was introduced to allow separately managed networks to translate and understand each others IP addressing scheme. It was then quickly adopted as a method to preserve public IP addresses. NAT takes either a source or destination address in a packet and translates that same source or destination address. Basic NAT or One-to-One NAT will always take IP 1 and translate it to IP 2. If traffic is returning back to IP 2, it will in turn be translated back to IP 1.
This type of NAT is seen when an organization is migrating IP schemes or if two organizations are merging but have overlapping IP addressing schemes in use. You will also see this used when a privately addressed server has a public IP dedicated specifically to it. Source NAT-ing is a method to specifically adjust source information while Destination NAT-ing is a method to specifically adjust destination information. When using either Destination NAT or Source NAT I can alter both the IP address as well as the layer four port number.
I could, for example, Destination NAT TCP Port 8080 on the outside to my local web server on Port 80 on the inside. I can also pick and choose which IP address to translate to based on TCP or UDP Port numbers. For example, I can Destination NAT Port 80 to my web server on internal IP 1, but if traffic were to enter on Port 21, that could translate over to my FTP server on internal IP 2.
This allows an admin to flexibly use a handful of public IP's. Many-to-One is also called Port Address Translation, NAT overload, or masquerading. When a host inside a network attempts to access resources on the outside of the network, NAT will create an entry in a table, Source NAT the packet, and send it on its way. When the packet returns to the router, it will reference the NAT table for this connection and destination the packet back to the proper inside host.
This allows multiple hosts behind a router to share a single public IP address, though each manufacturer and often model of router will have differing capabilities most can support around 65,000 simultaneous translations on a single IP. Virtually every network in the world utilizes NAT, from the connections at your house to the largest of enterprises.
He discusses different WAN technologies and features such as speeds, spans, and price points—including inexpensive options such as VPN. He then covers switches (the devices that connect computers in your building) and routers (devices that control the transmission of network data). Along the way, Greg shows how to build private connections, implement free networking over the Internet, build switch networks, and overlay-routed networks. He'll also introduce different routing protocols, such as OPSF link-state routing and distance-vector routing with RIPv2, EIGRP, and BGP.
Note that this course maps to domains 1 and 2 of the Microsoft Technology Associate (MTA) Networking Fundamentals certification exam (98-366).
- Understanding the technology: from dial-up to VPNs
- Working with hubs, bridges, and switches
- Ensuring hardware redundancy
- Using switching types and MAC tables
- Preventing bridge loops with STP
- Routing with routing tables
- Using NAT
- Securing your switches and routers
- Setting up firewalls
- Working with different routing protocols: RIPv2, OSPF, EIGRP, and more