Network Address Translation (NAT) Flashcards
Characteristics of IPv4 Address Space (mcq) REF IMAGE FOR CLASSES
Commonly implemented using
private IPv4 addresses, as defined in RFC 1918.
- Private IPv4 addresses cannot be routed over the internet and are used within an organization or site to allow devices to communicate locally
- To allow a device with a private IPv4 address to access devices and resources outside of the local network, the private address must first be translated to a public address.
- NAT provides the translation of private addresses to public addresses.
What is NAT used for
Conserve public IPv4 addresses
Why is NAT useful
Allows networks to use private IPv4
addresses internally and translates them to a public address when needed.
How does NAT operate
- A NAT router typically operates at the border of a stub network.
- When a device inside the stub network wants to communicate with a device outside of its network, the packet is forwarded to the border router which performs the NAT
process, translating the internal private address of the device to a public, outside, routable address.
How NAT Works (btr go watch video)
NAT Terminology - Inside
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- Inside local address
The address of the source as seen from inside the network. This is
typically a private IPv4 address. The inside local address of PC1 is
192.168.10.10.
- Inside global addresses
The address of source as seen from the outside network. The inside
global address of PC1 is 209.165.200.226
NAT Terminology - Outside
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- Outside global address
The address of the destination as seen from the outside network.
The outside global address of the web server is 209.165.201.1
- Outside local address
The address of the destination as seen from the inside network. PC1
sends traffic to the web server at the IPv4 address 209.165.201.1.
While uncommon, this address could be different than the globally
routable address of the destination.
What is Static NAT
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Static NAT uses a one-to-one mapping of local and global addresses configured by the network administrator that remain constant.
Why is Static NAT useful
Static NAT is useful for web servers or devices that must have a consistent address that is accessible from the internet, such as a company web server.
It is also useful for devices that must be accessible by authorized personnel when offsite, but not by the general public on the internet.
What is Dynamic NAT
Dynamic NAT uses a pool of public addresses and assigns them on a first-come, first-served basis.
How does Dynamic NAT work
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When an inside device requests access to an outside network, dynamic NAT assigns an available public IPv4 address from the pool.
The other addresses in the pool are still available for use.
NOTE: Dynamic NAT requires that enough public addresses are available to satisfy the total number of simultaneous user sessions.
What is Port Address Translation
Port Address Translation (PAT), also known as NAT overload, maps multiple private IPv4 addresses to a single public IPv4 address or a few addresses.
How does Port Address Translation work
With PAT, when the NAT router receives a packet from the client, it uses the source port number to uniquely identify the specific NAT translation.
Why is Port Address Translation useful
It ensures that devices use a different TCP port number for each session with a server on the internet.
6 Advantages of NAT
NAT conserves the legally registered addressing scheme by allowing the privatization of intranets.
NAT conserves addresses through application port-level multiplexing.
NAT increases the flexibility of connections to the public network.
NAT provides consistency for internal network addressing schemes.
NAT allows the existing private IPv4 address scheme to remain while allowing for easy change to a new public addressing scheme.
NAT hides the IPv4 addresses of users and other devices.
