Basic setup for Internet routing on 1811

Unanswered Question
Sep 28th, 2008

I just need to set-up my 1811 router to connect our LAN to the internet through our ISPs T1 router. It has a static IP address and we have a range of IP address that we may use without NAT. I have established a static IP on the FE0 interface and setup NAT and DHCP for the local network, but it doesn't route to the internet. I need help.

I have this problem too.
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Richard Burts Sun, 09/28/2008 - 18:50


My first question would be whether there was an appropriate default route on your router. My second question would be whether there is some problem in your address translation. We might find answers to these questions if you would post the config of the router.



disensee1 Sun, 09/28/2008 - 22:47


Thanks for you reply. The default route I have setup is

The refers to the ISP router's IP address.

I am unfortunately not able to supply the configuration from the router right now since it is at the office where I am trying to set it up. The NAT is setup to use the

FE0 IP address as the outside and

VLAN1 and VLAN2 as the inside.

I would just as soon use the switch ports on the 1811 as the inside NAT but could not figure out how to do that directly.



disensee1 Sun, 09/28/2008 - 22:55


Perhaps the question I should have asked, is "What are the basic steps to setup an 1811 router to use it behind an ISP router with a static IP?" I haven't been able to find any document that could tell me that, so I have just been taking shots in the dark and I appear to be missing the barn.



arupbiet2006 Mon, 09/29/2008 - 01:01


you don't send your configuration .its may be your nating config problem.1stly make a access list and then permit that access list by by interface after that prompt ovrld in outside interface.

Richard Burts Mon, 09/29/2008 - 04:12


Perhaps we can start with some clarification. In your original post you say this:"It has a static IP address and we have a range of IP address that we may use without NAT". Can you clarify whether the addresses are an address for your interface and additional addresses in the same subnet that you can use. Or is it an address for your interface and a separate subnet of addresses that you can use (on your LAN perhaps)?

To answer your follow up question I would suggest that these are generally the steps in setting up a router to provide Internet access:

- configure appropriate addresses on the outside and inside interfaces of the router.

- verify that the router can ping the next hop gateway address (the ISP router).

- configure a default route with the ISP router as the next hop.

- determine whether you need to translate addresses on the inside. if you do need to translate addresses then configure address translation.

- verify whether the inside interface can access the ISP router (extended ping with inside interface as source address) or whether some PC connected to the inside interface can ping the ISP router. (verify that the ISP is routing back for the addresses on the inside interface.

- determine if you need restrictions on traffic from your network going to the Internet. If so then configure appropriate access lists and assign them to the interfaces.

- determine if you need restrictions on traffic from the Internet coming to you. If so then configure an appropriate access list and assign it to the outside inteface.

- verify whether the router is able to ping to addresses in the Internet (verify that the router traffic gets out and that responses are routed back.

- verify whether the router inside interface or PCs connected on the inside interface are able to access addresses in the Internet.



disensee1 Mon, 09/29/2008 - 04:31


Thanks again for your response. Here is the basic scenario.

The FE0 interface is setup with a static IP address in the range supplied by the ISP.

It is connected to the ISP's router

I have defined DHCP for the internal network. The generic 192.168.x.x concept.

I have defined a default route as such

ip route XX.XX.XX.29

XX.XX.XX.29 is the address of the ISP's router

I do not need to restrict any access to the internet

I suspect my problem is my NAT setup.

I cannot ping the ISP's router or even the outside port.

I guess what I need is,

What do I configure for the inside interface?

I think the outside interface is straight forward, but I could have messed it up as well.



Richard Burts Mon, 09/29/2008 - 08:51


If you can not ping the ISP router or even the outside port then something is wrong. Is this router connected directly (physically) to the ISP router? Is it using straight through cable or cross over cable?

Perhaps it would help if you would post the output of show ip interface brief.

If you are doing DHCP using 192.168.x.x then I would expect the inside interface to be configured with a 192.168.x.y address. Perhaps you could post the DHCP config, the interface config for inside, and the NAT config?




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