Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

NAT Issue

Hi there,

I've got cisco 2620XM router.i'm configuring NAT on that. MY ISP has give us single(1) Public IP. so using that i want my user to use internet and using the same IP I want my remote user to access my mail server which is in my local LAN. How can I do that using single IP ? Please advice...


VIP Purple

Re: NAT Issue


not sure what exactly you mean: do you want the same user on your LAN to access the Internet and to access the mail server on your local LAN ? Or do you want a user on the Internet to access your mail server on your local LAN ?




Re: NAT Issue

Yes, you can do this.

Check the last configuration on this link.

hope this is what you were looking for.

New Member

Re: NAT Issue

Hi Georg,

In my case,My ISP has given me a Single public IP, I want my LAN user to use internet thru NATted IP on router which is given by ISP. Now i've got some remote(Sales Guys) users who r travelling very frequently. They connect internet thru Dial-up to some ISP. Now my remote user wants to access my mail server which is in LAN. So using same IP which is give by me ISP, how can I configure the same. Hope u'll get clear idea on my screnario.


New Member

Re: NAT Issue

I think you would want to use the following command:

ip nat pool library netmask

ip nat inside source list 10 pool library overload

Don't forget to build access-list 10 and permit your inside networks and to put ip ant outside and ip nat inside on the appropriate interfaces.


New Member

Re: NAT Issue

In 2620XM I am assuming fa0/0 for connecting to local LAN (private address space 192.168.0.x/24)

And Fa0/1 connecting to ISP having public IP(A.B.C.D)

Router LAN ip

Mail server IP and port no 25(SMTP)

The config will look like this.

Inteface Fa0/1

ip address A.B.C.D

ip nat outside

Interface Fa0/0

ip address

ip nat inside

ip nat inside source list 100 interface fa0/1 overload

ip nat inside static tcp 25 interface fa0/1

ip nat inside static udp 25 interface fa0/1

ip access-list 100 permit ip 192.168.0.x any

CreatePlease login to create content