Configure Cisco 1841 router for internet access using the cable modem/router.

[kramla]

I need help for configure a CISCO 1841 for internet access using the cable modem/router.
My network consist of:
1. A Cisco 2950 switch configured with two VLANs
• 10.10.10.0/24 GW: 10.10.10.1
• 10.10.20.0/24 GW: 10.10.20.1
2. A Cisco 1841 Router. Fa0/1 is connected to the switch for trunking and sub-interface.
Internally, everything is working fine. I can ping each network.
Now, I am going to setup the internet connection on the router fa0/0 with following commands.
• Int fa0/0
• IP Address DHCP
• No Shut
• IP NAT outside
• Int fa0/1
• IP address 10.10.30.1 255.255.255.0
• IP NAT inside
• No shut
• Access-list 1 permit 10.10.0.0 0.0.255.255
• IP NAT inside source list 1 interface fa 0/0 overload
• IP route 0.0.0.0 0.0.0.0 192.168.1.1
The internet is connected to a LinkSys cable modem / router (the router IP address is 192.168.1.1 and there is a DHCP scope setup for the 192.168.1.x network). I connect the 1841 fa0/0 to one of the ports on the LinkSys router.
From the CISCO 1841 I am able to get the IP for fa0/0 for the 192.168.1.x network and I also able to ping outside IP address. (for example 8.8.8.8). From the traceroute the first hop is 192.168.1.1, second hop is the gateway assigned to the LinkSys cable modem external interface, the final hop is the google DNS. (Working fine here)

Now, from one the workstation, I cannot ping outside IP. (for example, the IP for the workstation is 10.10.10.20/24 GW. 10.10.10.1). from the workstation I can ping the IP of the linkSys router (192.168.1.1) But when I ping 8.8.8.8, it times out. On the traceroute, the first hop is the gateway of the workstation (10.10.10.1), and second hop is the Linksys IP (192.168.1.1) and not able to get to the third hop which should be the external gateway assigned to the LinkSys router.

So Cisco router is able to route traffic to the external gateway IP assigned to the cable modem but not from the workstation. Any ideas?

Thanks

 

[iggsterman]

Does your 1841 have routes to 10.10.10.0 and 10.10.20.0 subnets? It does not appear so. Also, your inside intf is 10.10.30.1. Which device will route between 10.10.30 and the other 10.10.x ?

 

[USDOLLAR]

Kramla,
Try to login cisco 1841 and post your output of command show ip nat translation. You can try to add ip nat inside under Sub-interface of Fa0/1 and try again. Appreciate if you could post your 1841 configuration file.

BRG
HUONG