NAT ( Network Address Translation )questions and answers
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NAT
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NAT
Private IP addressing is defined in RFC1918 according which the following IP address blocks can be used with in an organization for private use:
• Class A network: 10.0.0.0 to 10.255.255.255
• Class B network: 172.16.0.0 to 172.31.255.255
• Class C network: 192.168.0.0 to 192.168.255.255
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nat network address translation questions and answers
private ip addressing is defined in rfc1918 according which the following ip address blocks can be used with in an organization for private use
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NAT ( Network Address Translation )
Private IP addressing is defined in RFC1918 according which the following IP address
blocks can be used with in an organization for private use: - Answer • Class A network:
10.0.0.0 to 10.255.255.255
• Class B network: 172.16.0.0 to 172.31.255.255
• Class C network: 192.168.0.0 to 192.168.255.255
what is NAT? - Answer The NAT protocol is used when connecting multiple devices on
internal private networksto a public network such as the Internet using a limited number
of public IPv4 addresses. It was originally designed for conserving IPv4 address space
because the IPv4 address space is not big enough to uniquely identify all devices that
need Internet connectivity.
when can you use NAT? - Answer typically NAT is used when a private IP address
needs to be routed in a public network, let's say internet. but it could also be used when
there is an overlap between intranets.
NAT uses the terms inside and outside, what do these means? and what their types? -
Answer Inside means internal to your network, and
outside means external to your network. NAT includes the following four types of
addresses:
• Inside local address: The IPv4 address assigned to a device on the internal network.
• Inside global address: The IPv4 address of an internal device as it appears to the
external network. This is the address to which the inside local address is translated.
• Outside local address: The IPv4 address of an external device as it appears to the
internal network. If outside addresses are being translated, this is the address to
which the outside global address is translated.
• Outside global address: The IPv4 address assigned to a device on the external
network.
what are the three types of NAT? - Answer • Static NAT: Static NAT is one-to-one
translation. Static NAT is particularly useful
when a device must be accessible from outside the network. (For example, when
a server with a static IPv4 address needs to be accessible from the Internet, that
server's private address can be translated to a public address.)
• Dynamic NAT: Dynamic NAT is many-to-many translation, using a pool of addresses.
When an inside device accesses an outside network, it is assigned an available
IPv4 address from the pool on a first-come, first-serve basis. When using dynamic
NAT, you need to ensure that there are enough addresses available in the pool to
satisfy the total number of user sessions. An example of when this type of NAT
could be used is when two companies that are using the same private address space
merge; dynamic NAT readdressing could be used as a temporary measure until the
entire network is readdressed.
• Port Address Translation (PAT): PAT is many-to-one translation; for example,
, it maps multiple inside local IPv4 addresses to a single inside global IPv4 address
by tracking port numbers. PAT is also known as NAT overloading. It is a form of
dynamic NAT and is the most common type of NAT. PAT is used in business and
home routers, allowing multiple devices to access the Internet, even though only
one public IPv4 address is available.
what is the command used to verify which addresses are currently being translated? -
Answer The show ip nat translations command is used to verify which addresses are
currently
being translated.
how do you configure static NAT? - Answer You first define inside and outside
interfaces, using the ip nat inside and ip nat outside interface configuration commands.
You next specify which inside local address should be translated to which inside global
address, using the ip nat inside source static local-ip global-ip global configuration
command
Router(config)# interface Ethernet 0/1
Router(config-if)# ip address 209.165.201.1 255.255.255.240
Router(config-if)# ip nat outside
Router(config-if)# exit
Router(config)# interface Ethernet 0/0
Router(config-if)# ip address 172.16.1.1 255.255.255.0
Router(config-if)# ip nat inside
Router(config-if)# exit
Router(config)# ip nat inside source static 172.16.1.10 209.165.201.5
how do you configure dynamic NAT? - Answer Like static NAT, you first identify each
interface as an inside or outside interface.
You then define the set of inside local addresses to be translated, using an ACL. The
next step is to define the set of inside global addresses to which the inside local
addresses will be translated, using the ip nat pool name start-ip end-ip. Finally, the ACL-
to-NAT pool mapping is defined by the following global configuration
command: ip nat inside source list {access-list-number | access-list-name} pool name
Router(config)# access-list 1 permit 172.16.1.0 0.0.0.255
Router(config)# ip nat pool NAT-POOL 209.165.201.5 209.165.201.10
netmask 255.255.255.240
Router(config)# interface Ethernet 0/1
Router(config-if)# ip address 209.165.201.1 255.255.255.240
Router(config-if)# ip nat outside
Router(config-if)# exit
Router(config)# interface Ethernet 0/0
Router(config-if)# ip address 172.16.1.1 255.255.255.0
Router(config-if)# ip nat inside
Router(config-if)#exit
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