Static NAT

[Najib Akbari]

I knew the concept and configuration of NAT and my confusion is :

for example : static (inside,outiside) 117.55.207.59 192.168.1.10 netmask 255.255.255.255

my confusion is the 'netmask' in syntax because static NAT is a one 2 one solution that we can use,

so what is the advantage of using subnet mask ? is it for binding a valid subnet to a privet subnet ?

or is it for binding a public one IP addr to a private subnet? or somthing else, then if its for binding

subnet to subnet then how static NAT works ?

thanks

[Federico Coto Fajardo]

Hi Sayed,

The purpose of the subnet mask is to give the range of addresses to be statically translated.

I am going to giev you an example...

static (in,out) 1.1.1.1 2.2.2.2 netmask 255.255.255.255

The above NAT translates the internal 2.2.2.2 to 1.1.1.1 and this is indeed a one-to-one translation.

static (in,out) 1.1.1.0 2.2.2.0 netmask 255.255.255.0

The above NAT translates the entire 2.2.2.0/24 to 1.1.1.0/24

static (in,out) 1.1.1.32 2.2.2.32 netmask 255.255.255.224

The above NAT translates 2.2.2.0/27 to 1.1.1.0/27

So, you see that the static NAT is a static translation but it can include an entire subnet or just specific IPs.

Hope it helps.

Federico.

[Najib Akbari]

Hello Dear Federico,

thanks for your usefull explanation, it has clarified my confusion but a little more clarification needs :

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when we run static Nat command ( one 2 one )then the xlate table builds and we can see which real IP is binded to which mapped IP by show xlate command.

but when we run a static command that binds a subnet 2 subnet then its shows by show xlate just a subnet binded to a subnet and its not clear that which real IP of the private subnet is binded to which mapped IP of the public subnet.

- so is it automatically binds the private subnet IPs to Public subnet IPs respectively ? bcz it should be clear when we wants to publish a server to internet that which private IP is binded to which Public IPs in the range of two subnets ?!!.

- in case that we want to bind a subnet 2 subnet, then can we use Static PAT ? or its just possible with static NAT only ?

so please give me more information.

thanks

Najeeb