Large Scale Networks Gateway

[xfrieyt]

Hello,

I need basic info. I am confused that large scale NAT. For example we have a single interface for ISP. There are 30,000 devices using Internet access simultaneously using NAT.Assume each device can have 5 connections to Internet open at any time. This would grater than TCP/UDP port lenght limit. In this situation, how to router (ISP router) behaves ?   

[balaji.bandi]

what router and model you are referring here.

First you need to start with Single Public IP with NAT configuration, when the X-Late and TCP multiplex full you get an error. I have worked environment there was no issue only for browsing, this may not be the case all the time. Depends on application.

you need to ask provider more IP address if the requirement is bigger. ( you need to Double NAT inside(i would not suggest, some application dont like it also).

[paul driver · Accepted solution]

Hello

If you have that of a large user base then one public nat address wouldn't be applicable you would use multiple public addressing in a NAT Pool and have users utilize those pool of public addresses in nat translation, With that many users you would also have resiliency and high availability  so dual nat rtrs would be applicable incorporating something like B2B nat but the concept of dynamic nat pooling would be the same as below 

example:

ip access-list 100 permit ip 10.1.0.0. 0.0.127.255 any
Ip nat pool PUBLIC 1.1.1.1 1.1.1.30 prefix-length 27 
ip nat inside source list 100 pool PUBLIC