Could someone please help me understand the concepts of NAT? I thought I understood how this works, but I'm confused about there being two public addresses, as opposed to just one public internet address.
My understanding on NAT is this:
Inside Local - The RFC 1918 private address or addresses before translation
Outside Local - The outgoing interface IP of the router connected to the ISP (is this also an RFC 1918 private address???)
Inside Global - The local IP address after translation
Outside Global - The real internet address
Please correct me here if I'm wrong.
When I've seen examples of the NAT translations, I understand the inside local address is the local private IP range, with the inside global address being the local address address after translation. What I don't understand is where the public addresses for outside local and outside global come from.
The reason I ask this is because when I configure PAT, I'd use the following command for example:
ip nat pool test 126.96.36.199 188.8.131.52 net 255.255.255.0 access list 10 permit 192.168.100.0 0.0.0.255 ip nat pool inside source list 1 pool test overload
I'd then apply the following on the inside local interface:
ip nat inside
With the following on the serial interface going to the ISP
ip nat outside
By definition, I've specified the NAT pool address to use, and specified the allowed networks with the ip nat inside command, so is there something additional I'd need to configure for the actual public addresses?
Any help would be appreciated, as I'm having a hard time trying to grasp the concepts here.