1801 ADSL Connection Problem

Unanswered Question
Nov 3rd, 2008

I have an 1801 router and am trying to connect to the internet. I have successful connection tests for the ATM0 and FE0 interfaces, but when I ping external addresses from CLI the best return I get is 40% and I can't connect to the internet / ping from LAN clients. I have set the LAN clients to use the default gateway which is the FE0 IP address, and to use the FE0 IP address as the DNS server.

I have attached the running config and connection results.

Any assistance would be greatly appreciated.



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Giuseppe Larosa Mon, 11/03/2008 - 06:34

Hello Philip,

in the running config I see:

ip route Dialer0

ip route FastEthernet0

the second one should be removed it is only dialer0 the interface to the internet

Hope to help


PhilipBelgian Mon, 11/03/2008 - 06:41

Thanks for the reply Giuseppe.

Without the FastEthernet0 route the FastEthernet0 Test Connection fails as 'SDM tries to ping DNS servers, however there is no configured route through the selected interface'

Also the internet connection from LAN clients on the same subnet as FE0 do not work with or without the FE0 route - they just get a page cannot be displayed message.

I feel as though I am very close, but just missing a/some minor detail(s).



Giuseppe Larosa Mon, 11/03/2008 - 06:49

Hello Philip,

I never used SDM but having two default routes one going to internet and one pointing to in the internal LAN is not a good thing in a Cisco router:

it will try to use both in a form of load balancing and this could explain your results

Hope to help


PhilipBelgian Mon, 11/03/2008 - 06:53

Thanks again Giuseppe,

I will try again without that line.

I did the config using CLI, but just used SDM to test the connection and produce a report for the failure to connect.

I will post the updated reports shortly when the line has been deleted.


PhilipBelgian Mon, 11/03/2008 - 07:39

I have altered the config as suggested and attach the connection test outputs and running config.

My LAN clients get a 'waiting for http://www.xyz.com' and then a page cannot be displayed message.

Also I cannot ping external addresses, but get success from pinging external addresses with CLI.

Giuseppe Larosa Mon, 11/03/2008 - 09:27

Hello Philip,

let's divide the two issues:

- pinging public ip addresses from LAN clients

- DNS resolution


on the LAN client

have an ip address 10.0.0.x

configure as gateway

try from a PC client to ping a public ip address that answers from the router.

verify on the router if a NAT entry is created with:

show ip nat translations

you should see an entry where the inside local is the PC ip address 10.0.0.x

Feel free to post the output of show ip nat translations

b) for DNS

make an attempt to use

ip name-server

int fas0/0

ip helper-address

First of all ip reachability has to be achieved

Hope to help


PhilipBelgian Mon, 11/03/2008 - 10:19

Hi Giuseppe,

I don't really know how to explain this!

I tried what you said and was able to ping externall ip addresses 100% success, but not domain names and no internet connection.

For some reason I changed my SBS2003 box default gateway to the FE0 IP address ( and then changed my client back to use my SBS2003 box as the default gateway and internet connection works like a dream.

I am happy that I have the connection working, but am confused as to why this is - do you have any ideas?

Also I can't receive mail to the exchange server anymore, but I assume that is a firewall issue?

Thanks for your help.


Giuseppe Larosa Mon, 11/03/2008 - 10:37

Hello Philip,

I'm happy you have found a solution to your issue.

Do you mean you have a Windows Small Business Server with SBS2003 box ?

this was part of the networking infrastructure before


probably this all in one box server is able to act as internal DNS for your PCs (and/or your PCs were configured to use it as their DNS server)

>> Also I can't receive mail to the exchange server anymore, but I assume that is a firewall issue?

I would point to an MTU issue you have placed

mtu 1492 inside the dialer interface but this is PPPoA not PPPoE I would try to use mtu 1500 within dialer0 interface.

Of course if you have also a firewall this is the second item to be checked.

Hope to help


PhilipBelgian Tue, 11/04/2008 - 01:12

Hi Giuseppe,

Yes we use small business server 2003 - which has always been on the network.

The PCs are configured to use it as the default gateway and as dns server, however i did change some of the internal clients to use the 1801 as the default gateway and dns server and performed ipconfig/flushdns on them, but they could only ping external ip addresses and could not resolve external domain names.

Now that I have the connection working I will set to work on the firewall and then VPN config!

Thanks again for your help!



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