Configure Cisco router overload NAT (IOS 15)

[Naltharial]

Greetings,

I am attempting to configure a Cisco 2901 router using IOS 15 to  properly perform NAT/PAT translation between LAN and the internet  connection. I've configured DHCP pool for the local interface (GigabitEthernet0/1), which  works properly. The WAN interface (GigabitEthernet0/0) is configured to obtain its own IP by  DHCP from the ISP. I can work on the LAN computers and I can access the  internet directly from the router (using, for example, telnet and  router's ping commands). The problem is, NAT does not work properly and connection from the LAN  interface does not reach the WAN interface.

Attached is the complete configuration, hoping someone finds the problem I have missed.

Thanks!

[Rozsa Illes]

Hello Primoz,

You have got ip route disabled:

no ip routing

It has to be enabled:

ip routing

Aside from this I would enable CEF as we can see high cpu without it (it will impact the performance of the router at least):

ip cef

and on the interfaces (gig0/0 and gig0/1):

ip route-cache

One more note about the config. You have got the default route pointing to the router's own interface. This will create a connected route and we will ARP for every destination IP which does not have an ARP entry which is not very efficient.

I would recommend to reconfigure the route command so that you either use the next hop router's IP address (if you know what IP the ISP is using) or you use the dhcp keyword at the end of the route.

I hope it helps.

Warm Regards,

Rose