Primary link - ADSL Backup Link - ISDN

[katchme]

Hi all,

I'm currently run ADSL as my primary link for our WAN link at work, however, this link oftens fail. I have 2 cisco 1600 series router (one at each location) sitting there to use as an ISDN backup link. At the moment, everytime the ADSL fails, I have to manually setup the PC, cisco router, server etc... to pick up the ISDN link and start dialling out, a very manual process.

What I have to manually do at the moment (when ADSL fail) is to change the default gateway and the router scope in DHCP on the Domain Controller at the remote site to pickup the new default gateway e.g. 172.16.2.51 from the active cisco router (ISDN), and the from the other end, I have to add the "host route" (with the default gateway of the cisco router from this end e.g. 172.16.1.51)to any of the servers that I want it to talk to the DC from the othersite. Once I've done all this then the ISDN is up and running and I can start doing my normal business.

As you can see this is not very productive. What I want to know is there anyway I can setup the two cisco routers to pick up the fail ADSL link and automatically promote itself to be the main link while the ADSL service is down?

A sincere thank to those that could help or point to me the right direction.

katchme

P.S It helps if I could have a sample cisco configuration.

 

[JJ1]

I think you might find this configuration helpful.

Normally Serial0 is UP, but when it fails, there will be a 10 second delay before the Dialer 1 interface goes active.

!
interface Serial0/0
description ----Colt 2Mb/S link ----
bandwidth 2048
backup delay 10 30 <-- Wait 10s before ISDN, 30s before reverting
backup interface Dialer1
ip address X.X.X.X 255.255.255.252
no ip route-cache
ip summary-address eigrp 10001 X.X.X.X255.255.255.240 5
no ip mroute-cache
down-when-looped
!
interface BRI1/0
description ---- Our Backup ISDN Interface ----
no ip address
encapsulation ppp
dialer pool-member 1 <------Dialer interface to use
isdn switch-type basic-net3
isdn caller 0655555
ppp authentication chap
!
interface Dialer1
ip unnumbered Loopback0
encapsulation ppp
ip summary-address eigrp 10001 X.X.X.X 255.255.255.240 5
dialer pool 1
dialer remote-name remote_host_name
dialer idle-timeout 900
dialer string 0655554
dialer load-threshold 128 either
dialer-group 1
ppp authentication chap
ppp multilink
!

I don't fully understand your question, but I think this might be helpful for you.

 

[katchme]

Hi JJ1,

Thank you for your input. I will try what you show me above. Just to explain what I'm trying to say before.
Basically, I'm running ADSL as my primary link and the router to run it is provided by the service provider, it is just a standard ADSL router modem.

I got 2 cisco routers which act as a backup ISDN link.

*******
Site 1

1 cisco router
1 Domain Controller (W2K)use for local authentication, running DHCP. It uses DNS from a server at site 2.
An ADSL router which act as a default gateway. IP address is X.X.2.51

Site 2 (Head Office)

-A few Domain Controllers
-A Terminal server mainly access by users from site 1.
-1 cisco couter
-ADSL router which act as a gateway. IP adress is X.X.1.51

*******

Everytime the ADSL link b/w 2 sites goes down. I have to manually bring up the ISDN link by doing the following:

From site 1:

1) Change the default gateway on the DC to the IP address of the cisco router (new gateway i.e. X.X.2.50).
2) Change the &quot;router scope&quot; IP address under DHCP on the DC to the new IP address i.e. X.X.2.50
3) Change the default gateway on the DC under TCP/IP properties to the new gateway i.e. X.X.2.50
4) Once I have done all these on the Domain Controller at Site 1, I get all users to restart their PC to pick up the new information.

From site 2 (Head Office)

1) I logon to the terminal server to add a &quot;host route&quot; so that this terminal can get through to Site 1 with the new gateway

i.e route add X.X.2.0 mask X.X.X.X X.X.1.50

X.X.1.50 is the IP address of the cisco router from site 2.

After I got all this done, then I can ping the remote server from site 1 and and users from site 1 can start access terminal server at site 2.

Because the ADSL routers are independent of the cisco router (ISDN). What I want to know is if ADSL fail, how can I get my cisco to automatically pick the fail network and start a live network b/w 2 sites without me manually going through all the process above.

The ISDN link is always ready. It just needs to be trigger to go live and active.

thanking you again and those that help!
katchme.

 

[gaveeve]

Katchme, do you have to manually rewire also? If not is there a switch or something in there?
There is a protocol called HSRP specifically for this but it is Cisco proprietary.
My thought is that if you could get your cisco routers to do the routing with the ADSL routers in the path(but not routing) you might be able to use what JJ1 was saying or dialer watch. Let me know about the wiring.

 

[katchme]

Hi,

No I don't have to do any wiring. All wiring remain as it is. I just need to make the change as describe earlier.

katchme.

 

[ewaterke]

You should configure HSRP on the Ethernet inerface of both router.
HSRP will give a virtual IP address to the active router and this address has to be use as default gateway. By correctly setting the weights in the hsrp config, you can manage that the ADSL router is the active one and when the ADSL line fails, the ISDN router will become active.

For more info check HSRP on the Cisco web site.

Regards