when do we use ip nat outside ?

satishtech

I normally use ip nat inside , never used ip nat outside ?
when is this used ?

Mooseboost

I guess a rough explanation would be that nat outside is used for outbound traffic on the WAN interface.

Here is a good link for NAT:

The Inside and Outside of NAT

satishtech

confused ,

ip nat inside source static 155.1.13.1 155.1.23.1 ip nat outside source static 155.1.23.2 155.1.13.2

which interfaces on R3 are the IP's 155.1.13.1,155.1.23.2 assigned ?

Deathmage

satishtech wrote: »

confused ,

ip nat inside source static 155.1.13.1 155.1.23.1 ip nat outside source static 155.1.23.2 155.1.13.2

which interfaces on R3 are the IP's 155.1.13.1,155.1.23.2 assigned ?

ip nat inside source static 155.1.13.1 (SOURCE Address - Private) 155.1.23.1 (DESTINATION Address- Public)

ip nat outside source static 155.1.23.2 (SOURCE Address - Private) 155.1.13.2 (DESTINATION Address- Public)

You'd then assign the ip nat inside on the inside local address, typically the interface on the router connection to your companies LAN. ip nat outside would be on the interface on the router that is connection to like say your cable modem that has a reserved block of addresses. Say for instance your ISP gives you a block of a /29 or a 255.255.255.248 which is 8 addresses (6 usable) and your range is 172.16.50.0 0.0.0.7. Typically the 1st address in that range is for the modem, so I'd say 172.16.50.2 is free. You'd put the 172.16.50.2 on the interface with the ip nat outside function attached to it.

Also in-case I read to far into this, like I always do. the inside source static address is what it looks like external to the outside global address. 13.1 looks like 23.1 on the other side of the router going out to the internet. outside source static is basically the reverse, 23.2 going back into the router and into your LAN gets translated into 13.2 on your local LAN.

Does that makes sense?

satishtech

The serial interfaces on router R3 ( link above 2nd post)
are assigned 155.1.13.3 and 155.1.23.3
The static NATing is for 155.1.13.1 and 155.1.23.2.
I usually have done static nat , assigning an internal
web server with a NATed Public IP, but in the above diagram
I was wondering where IP's 155.1.13.3 and 155.1.23.3 are assigned?

james43026

The difference is this, IP nat inside defines NAT translations for inside hosts only, while IP nat outside defines NAT translations for outside hosts only.