Dial Backup for Frame Relay using Floating Static Routes

[donmorales]

Our clients has a Cisco 3745 Router in its main office, and a Cisco 3660 as a backup router.

Each branch has a Cisco 2620 router connected to the Cisco3745 via Frame Relay. If at anytime the frame relay connection is disrupted, the branch router should dial the Cisco 3660 router via ISDN.

The present configuration works. However, the branch router immediately dials and connects to the first two numbers. Can anyone spot my mistake in the attached configuration?

[parvees123]

Hai,

It was becoz you have entered the follwing commands previously

ip route 192.168.241.0 255.255.255.0 192.168.248.241 200

ip route 192.168.241.0 255.255.255.0 192.168.248.242 200

as the AD is same for both these routes it dials both of the numbers.

regards

Parvees M

[donmorales]

Hi Parvees,

Thanks for your reply.

The reason why I have these lines is because there are four ISDN lines at the Main Branch router. If the first line is occuppied or non-operational, I want the branch routers to dial the second number, and so on.

I have also tried increasing the metric of the second line to 210, the third to 220 and the last line to 230. But it still dials the first two.

How do I make it dial the first one, and dial the next one only if the first connection is unsuccessful?

regards,

don

[donmorales]

Hi Parvees,

Thanks for your reply.

The reason why I have these lines is because there are four ISDN lines at the Main Branch router. If the first line is occuppied or non-operational, I want the branch routers to dial the second number, and so on.

I have also tried increasing the metric of the second line to 210, the third to 220 and the last line to 230. But it still dials the first two.

How do I make it dial the first one, and dial the next one only if the first connection is unsuccessful?

regards,

don

[parvees123]

HI Don,

You delete the ad of first route to 241. i.e,

ip route 192.168.241.0 255.255.255.0 192.168.248.241

ip route 192.168.241.0 255.255.255.0 192.168.248.242 210

ip route 192.168.241.0 255.255.255.0 192.168.248.243 220

ip route 192.168.241.0 255.255.255.0 192.168.248.244 230

This will defentely do as it will take the first one as default route to the destination...

If you find this answer ok, please rate my reply.

Regards

PSM

[donmorales]

Hi Parvees,

I cannot delete the AD even on the first route because this will defeat the purpose of the floating static route.

The AD will be 1 and will defeat the AD of the route learned on OSPF which is my preferred route. This will prompt the ISDN BRI interface to dial even when the Frame Relay (with OSPF) link is up.

Any other ideas?

Regards,

Don

[Richard Burts]

I think I see what is causing this behavior. Your dialer map has 4 statements and 4 different addresses:

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585493

dialer map ip 192.168.248.242 name Ahli_MainB broadcast 17585498

dialer map ip 192.168.248.243 name Ahli_MainB broadcast 17585487

dialer map ip 192.168.248.244 name Ahli_MainB broadcast 17585491

and your static routes have 4 different routes all for network 192.168.241.0 to the 4 different numbers:

ip route 192.168.241.0 255.255.255.0 192.168.248.241 200

ip route 192.168.241.0 255.255.255.0 192.168.248.242 200

ip route 192.168.241.0 255.255.255.0 192.168.248.243 200

ip route 192.168.241.0 255.255.255.0 192.168.248.244 200

in effect your floating static routes have 4 equal cost paths to the destination and the router will try to do load balancing and open multiple paths to the destination.

I do not understand why you have 4 addresses in the dialer map. But to accomplish what you say you want which is to try to dial the first number and only dial the second if the first does not work I would suggest that you change the dialer map and have 4 dialer maps all with the same remote address - like this:

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585493

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585498

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585487

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585491

and I would remove the last three of the floating static routes.

If you change the configuration this way you will have a single floating static and 4 dialer map statements which will try to call each of the 4 numbers in order if the previous ones do not work. And it will not call additional numbers if a previous one does work.

Try this and let us know what happens.

HTH

Rick

[donmorales]

Hi Rick,

The reason why I have 4 addresses in the dialer map is because there are 4 BRI ports on the remote router each with a unique ip address and phone line.

In this Hub and Spoke network, all branches dial up to the Hub router which has 4 BRI interfaces. If the first line is already occuppied, the spoke or branch router should dial the next number (and so on).

I tried using only one address by using the Loopback0 interface address on the remote router. This time, when the Frame Relay link goes down, the spoke does not even dial.

Is it wrong to use floating static routes on a hub and spoke configuration?

[aservin]

I think this link can help you:

http://www.cisco.com/univercd/cc/td/doc/cisintwk/idg4/nd2010.htm

I am not a ISDN expert, but if you put different dial strings in the dialer interface it think if the first number is busy, it will automatically dial to the next one.

-as

[kamlesh.sharma]

Hi,

Put an static route like this

ip route 192.168.241.0 255.255.255.0 bri0/0 200

and dialer map like this

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585493

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585498

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585487

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585491

Than and regards

Kamlesh SHarma

[donmorales]

hi as,

you may have noticed that i am not using a dialer interface but a dial map in the BRI interface configuration. do i need to change my config using dialer interface instead of floating static routes?

does anyone have any other ideas please?

don

[Richard Burts]

Don

I do not think that you need to change from configuration on the BRI to dialer interface. Many of us believe that dialer interface is more recent, more flexible, and more capable that BRI interface configuration and prefer to use dialer interface. But you should be able to accomplish what you need with configuration of the BRI interface.

I believe that a large part of your problem is due to the configuration of the router with 4 BRI interfaces each with a different IP address. As several of us have pointed out the usualy way to achieve redundancy of trying the first number and if it does not answer to dial a second (and third and fourth) number is to have dialer maps with the same remote address and different phone numbers. But this is complicated when the other router has different numbers on each BRI. The alternative is to have 4 different dialer maps (each with one of the remote addresses). But that leads to your original problem that the router will have multiple equal cost routes and will attempt to dial on both B channels when it begins dial backup.

HTH

Rick

[kamlesh.sharma]

Hi,

As per your config that main BRI0/0 interface are having ip address in the same subnet.and i just want to remove equal cost route from your routing table so put the static route same as given above ultimatly you need only one route to main office no 4 for diffrent map ip.second thing dialper map will be the same as you have configured i was wrong in dialer map

dialer map ip 192.168.248.241 name Ahli_MainB broadcast 17585493

dialer map ip 192.168.248.242 name Ahli_MainB broadcast 17585498

dialer map ip 192.168.248.243 name Ahli_MainB broadcast 17585487

dialer map ip 192.168.248.244 name Ahli_MainB broadcast 17585491

Thanks

Kamlesh SHarma

[donmorales]

Gentlemen,

Thank you all for your time. We are finally beyond that initial problem that I had of the branch routers dialling two numbers from the start.

I removed the "PPP Multilink" line on the BRI Interface configuration. Retained the same dialer maps and the same floating static routes.

The first problem is solved, thank you. Please note the new problem which I now open a new topic for.

Regards,

Don