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getting started with NAT

nycjungle
nycjungle asked
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i have a cable modem conncetion, and a cisco router 2621 with IOS 11.3, i want to NAT a laptop running mandrake and a desktop running win98...is it possible to use NAT with 11.3 or do i need to upgrade my IOS? secondly, how would i go about actually setting up the NAT? please be as specific as possible...
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Commented:
NAT was released with 11.2 so you are OK there, but are you sure you have IP Plus or Enterprise Edition IOS?  You can either look at the name of the image you booted from, or just go to config mode and type:

ip nat ?

If it gives you options, you are in business.  If it says the command is not recognized, you will need a different version of the IOS.
Steve JenningsSr Manager Cloud Networking Ops
BRONZE EXPERT

Commented:
There's a complete - and suprisingly good - explanation of NAT and various ways to implement it on the Cisco site.

However, in case you are really lazy . .  .

Assume a serial 0/0 interface IP 1.1.1.1 and an ethernet 0/0 interface of 192.168.1.1 on your 2621 and you want several machines to be able to access the internet . . . and the only "legitimate" address is 50.50.50.1. (This is a little bit unrealistic)

ip nat inside source static 192.168.1.1 50.50.50.1
interface f0/0
ip nat inside
interface s0/0
ip nat outside

This way, when your 192.168.1.1 machine heads for the internet, the address will be changed from 192.168.1.1 to 50.50.50.1 for routability on the internet. The process will be reversed when on the return path.

Most small businesses with a Cisco router and an internet connection use a different NAT feature called inside global address overloading.

Good luck.
Steve



Author

Commented:
i have version 11.3(2)XA4......do i have the NAT ability?

Commented:
You need to either look at the name of the image you booted from and compare it to the table on this page:

http://www.cisco.com/warp/public/cc/pd/iosw/iore/iore113/prodlit/731_pp.htm

or you can follow the directions I listed in the previous post:

You can either look at the name of the image you booted from, or just go to config mode and type:

ip nat ?

If it gives you options, you are in business.  If it says the command is not recognized, you will need
a different version of the IOS.


Hope that helps (again)

Author

Commented:
i only have 32 megs of ram in the router, and 16 of flash, what is the latest version i can upgrade to that i can NAT with?
Steve JenningsSr Manager Cloud Networking Ops
BRONZE EXPERT

Commented:
If you have NAT on the release that you are currently running, why are you upgrading? Have you done what scraig suggested?

Steve

Commented:
To add to that - I just looked and the only post 11.3 versions of IP Plus that don't take 40 Mb is some 12.0 Early Deployment releases which probably wouldn't be recommended for stability reasons (original 12.0 stuff wasn't considered extremely stable).  However, if you go up to 40 MB of RAM you will be able to go to 12.2 IP Plus.  In other words, I would either add the extra RAM and go to the newest version or stick with 11.3 assuming you have IP Plus.  If you don't, you can't get 11.3 and you will be basically forced to upgrade your hardware to run a stable version.

Author

Commented:
yeah i tried that, it says ip nat is an unrecognized command.....i downloaded all of the latest versions of 12.2....enterprise plus and so on, don't know which one to use and if i have enough memory for it

Commented:
I meant to mention - your Flash is fine for the newest version of IP Plus.

Commented:
Also - one thing that I meant to mention before - have you thought about performing NAT on the cable modem/router?  These generally perform NAT out of the box.  
Les MooreSr. Systems Engineer
BRONZE EXPERT
Top Expert 2008

Commented:
No comment has been added lately. It appears this question has been abandonded so it's time to clean up this TA.
I will leave a recommendation in the Cleanup topic area for this question:

I recommend: split points - scraig84 and SteveJ

if there is any objection or other expert commentary to this recommendation then please post in here within 7 days.

PLEASE DO NOT ACCEPT THIS COMMENT AS AN ANSWER!

thanks,
lrmoore
EE Cleanup Volunteer
---------------------

Commented:
Finalized as proposed

SteveJ see:
http://www.experts-exchange.com/Hardware/Routers/Q_20515661.html

modulo

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