Cisco 2800 ADSL Failover

[parmstrong5]

Hi, am having trouble trying to setup a 2800 series router as a failover device (please bear in mind that I am fairly new to IOS).

The device has two ADSL modules installed which will be used as a direct connection to the ADSL lines rather than go through a seperate modem.

I am looking for the config so I am able to connect to either connection and should the primary connection fail the secondary connect takes over.

I have been trying to configure this on and off for a while however am struggling even to get the router to successfully connect to the ISP.                

[Peter Paluch]

Hi Phil,

The easiest way of configuring a backup connection is to simply define a pair of static default routes, each having a different trustworthiness (we call it Administrative Distance, AD, in Cisco parlance; lower number is better). The route with the better AD will point to the primary ISP and should the connection to the primary ISP fail, this route will be replaced by the other pointint go the backup ISP.

This is the basic simple idea. Your configuration will need to be slightly more sophisticated because you are probably going to perform NAT which has to take the outgoing ISP into account (each ISP is going to assign a different public IP to you so you need to perform NAT accordingly), and also, because the virtual Dialer interface that is going to represent your ADSL session to a particular ISP will not go down even if the ADSL connection is broken, we will probably need to configure an active ping test to verify the connectivity.

Perhaps if you could attach your existing configuration and tell us slightly more about your setup we could come up with a suggestion of how to proceed.

By the way, the topic of this discussion is more relevant to WAN Routing and Switching, not LAN - would you mind transferring this thread to that section? Use the Move discussion link in the Actions box on the top of the page.

Best regards,

Peter

[parmstrong5]

thanks for the response ( have moved the thread as well )

my existing configuration is absolute garbage, as this is something I go back to when I have little or no other work to deal with.  I understand what you mentioned and is what I am trying to achive though have little reference to work from as everything I find uses external modems as a segway and I have little expierence dealing with routers using IOS, usually deal with switches.

failed to mention that the router will need to act as the DHCP on top of this.

Really something to refer to in the encapsulation of the scenario

[Peter Paluch]

Phil,

Okay, please capture the output of the following commands in your terminal program and post it here as an attachment (the attachment can be added after clicking on the "Use advanced editor" when writing a reply).

show version

show running-config

show inventory

I also need to know:

• which ADSL interface is primary and which is secondary
• whether the ADSL providers use PPPoE or PPPoA, and what VPI/VCI they're using
• whether the ADSL providers use PAP or CHAP
• whether there is a unique IP address to any of these providers you can use for connectivity tests

Thank you!

Best regards,

Peter

[parmstrong5]

Have attached the mess that I have currently created.

Both ISP use the same settings

PPPoA

VPI 0 VCI 38

CHAP

IP is obtained automatically

[mfurnival]

It looks as if ATM0/2/0 is your BT connection and ATM0/3/0 is your other connection (but this one does not seem to be configured). You need to configure ATM03/0 with the details provided by your provider and then create another dialer interface (e.g. dialer2) where you configure your PPP bits and pieces. ATM0/3/0 is associated with this dialer with the "dialer pool" and "dialer group" command.

Then you would configure a second static route something like:

ip route 0.0.0.0 0.0.0.0 dialer2 10

(the 10 at the end gives it a higher admin distance meaning it will only come in to play when dialer1 is down).

You would also need to add another NAT statement along the lines of:

ip nat inside source list 1 interface dialer2 overload

[Peter Paluch]

Hello Phil,

Your current configuration is indeed broken in some places - deactivated routing, deactivated IP CEF, VPDN being enabled... I suggest starting from a completely clean configuration - that is going to make our troubleshooting easier if you don't mind. Issue the erase startup-config command and then reload your router using the reload command (if it asks you to save the current configuration do not allow it to save anything - you would just put back the current wrong configuration).

Please find the attached file. In it, there are commands relative to a clean running-config. They should put your configuration into a basic clean state in which the ADSL connections should come up. Edit the file, replace the capitalized values (passwords, the CHAP logins and passwords) as necessary, and then paste the contents directly to the router in the configure terminal mode - preferably not all at the time, better in parts. I hope I did not make any typo - please be sure to check for any error messages while pasting the file.

After you do this, please again attach the output of the show running-config to see how your configuration looks like, and also include the following command outputs:

show ip route

show ip int brief

show int di1

show int di2

Thank you!

Best regards,

Peter

[parmstrong5]

I am getting an error when entering the config on both dialer lines

ppp chap hostname *******@*******.com ppp chap password ********

                                                           ^

% Invalid input detected at '^' marker.

is this because the hostnames are email addressess?

[parmstrong5]

error is point to the ppp bank prior to the chap password entry

[Peter Paluch]

Hi Phil,

No, I don't think the @ sign is making any troubles here - I've seen and configured similar hostname myself quite often. However, are you absolutely sure you have encapsulation ppp already present on the Dialer interfaces? If not, the encapsulation is HDLC, not PPP, and PPP-related commands will be rejected.

Best regards,

Peter

[parmstrong5]

Yeah encapsulation ppp is setup on both dialers prior ro entering the username and password details

[Peter Paluch]

Phil,

One more comment - what you posted is a single line that combines both ppp chap hostname and ppp chap password commands. However, these are two distinct commands and shall be entered each on a separate line:

ppp chap hostname ....@......com

ppp chap password XXXXXX

Are you entering them in this way?

Best regards,

Peter

[parmstrong5]

am now

[Peter Paluch]

Hi Phil,

Okay, and are they accepted now, or still no luck?

Best regards,

Peter

[parmstrong5]

Appears to be connecting to ADSL line though am unable to pass data through router to a node (no Internet access)