Cisco 2620 nat problem

[ichybod]

can you use nat on cisco 2620 router with only a single interface or do you need 2 interfaces to make it work?

 

[oj88]

It depends on what you're trying to achieve. If you're connecting to a frame relay or LL network, you'll definitely need another interface, typically a serial port to connect to your service provider. You can then define which interfaces belongs to the "outside" (or unsecure) and the "inside". (the secure network)

Using just one F0/0 port would require you to configure sub-interfaces and use trunking (ie. isl or 802.1q), and terminate this to another trunk-capable device such as a switch. This setup is also known as a "router-on-a-stick". You can then define which logical sub-interface belongs to the inside and outside network.

Ex.

interface FastEthernet0/0
no ip address
duplex auto
speed auto
!
interface FastEthernet0/0.1
description Connects to the Internet
encapsulation isl 1
ip address 201.25.23.3 255.255.255.240
no ip redirects
ip nat outside
!
interface FastEthernet0/0.2
description Connects to the LAN
encapsulation isl 2
ip address 192.168.10.254 255.255.255.0
no ip redirects
ip nat inside
!
ip nat inside source list NATpool interface FastEthernet0/0.1 overload
!
ip access-list standard NATpool
permit 192.168.10.0 0.0.0.255
!
Orlando Palomar Jr
CCIE# 11206, CCNP
CIPT Operations Specialist
Phil-Data Business Systems, Inc.