Forum Replies

1. Hello Sumit

   This is a very good question because the terms used with NAT can become very confusing. Let’s say you are the Inside Host and you are connecting to a web server which is the Outside Host like so:

   //cdn-forum.networklessons.com/uploads/default/original/1X/eb1ecaeb2f794f41704468d582b014dced2ffa16.png

   You can see that the packet leaving the inside host and travelling towards the NAT router has:

   • Source Address: Inside Local - a private address such as 10.10.10.5
   • Destination address: Outside Local - the public IP address of the outside host such as 2

   ... Continue reading in our forum

2. Hello Maodo

   Don’t worry, you are reading up on CCNA material. Rene is referring to the fact that the Outside Local and the Outside Global addresses are the same. These however can be configured so that they are different. That is, the destination IP address can also be translated by NAT. It is this configuration alone that is outside of the CCNA curriculum. Not to worry, the rest is definitely covered within the CCNA curriculum.

   I hope this has been helpful!

   Laz

3. Thanks for your explanation, Lazaros.

   My question was no so technical. A CCNP lesson telling about CCNA scope ; I thought, it’s Copy/Paste error. Now, I understand that one lesson can belong to CCNA and also be re-used, without any change, in CCNP or CCIE courses. I found below the three (CCNA, CCNP, CCIE) links having the same NAT lesson (the lesson that was originally written for CCNA).

   …/ccna-routing-switching-icnd1-100-105/how-to-configure-dynamic-nat-on-cisco-ios-router/
   …/ccnp-route/how-to-configure-dynamic-nat-on-cisco-ios-router/
   …/ccie-routing-switchin

   ... Continue reading in our forum

4. Hello Sumit

   There are two types of translation entries: Simple and Extended. A simple translation entry maps one IP address to another. The keyword extendable which indicates an extended translation entry indicates that the translation entry will map an IP address and port pair to another. The extended translation includes the port. An example of such a configuration is the following:

   ip nat inside source static tcp 192.168.1.4 25 199.198.5.1 25 extendable
   ip nat inside source static tcp 192.168.1.3 21 199.198.5.1 21 extendable
   ip nat inside source static t

   ... Continue reading in our forum

5. Hello Chris

   This is a very valid question. Essentially, in a command such as the following, the prefix-length parameter is essentially a sanity check.

   NAT(config)#ip nat pool MYPOOL 192.168.23.10 192.168.23.20 prefix-length 24

   You could have easily used the prefix length of 23 or 25 and it would work correctly with the above IP addresses. However, it is always best practice to confirm that you use the real prefix length of the actual subnet in question.

   I hope this has been helpful!

   Laz