ISDN multiple dial option

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Feb 21st, 2008
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Hi,


I would like my ISDN couter to dial two different numbers/IP. In case the firt number is not available it should dial the second number. could you tell me what is the command?


thanks,

Arana

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Richard Burts Thu, 02/21/2008 - 07:27
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Arana


It is possible to have the ISDN router attempt dialing a first number and if it does not answer to dial a second number. The details of how to do it vary depending on whether you are configuring dialer strings or dialer maps. But essentially what you do is to configure the primary number as you are already doing and then to configure a second line like that with the secondary number. If you would post the config from your router we could make specific suggestions about how to do it.


HTH


Rick

rana_beech Thu, 02/21/2008 - 08:03
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Hi Rick,

Thank you for the response.

I am using 'dialer map ip 203.117.12.7 name ABC_dial_R1 00163752911'


so I just put another line below like this 'dialer map ip 203.117.25.19 name ABC_dial_R3 00163752911'

Do I have to give any priority?


Thanks,

Arana

Richard Burts Thu, 02/21/2008 - 08:22
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Arana


What you have is very close. But both dialer maps have the same number to dial. I understood from your original post that you wanted to dial a first number and if it did not work then you wanted to dial a second number. So you need a dialer map like the first one with a different number to dial.


You do not need to specify priority. The router will try the first line as primary and go to the backup if the primary does not answer.


I am not clear about the second dialer map with a different IP address. Depending on how you initiate the call (what is the interesting traffic) the router may initiate calls to both IP addresses. But that is more a matter of how routing is set up on your router and not so much a question of how you configure the ISDN.


HTH


Rick

rana_beech Thu, 02/21/2008 - 14:41
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Hi Rick,

Bothe R1 and R3 are at the same location and it uses the same number. Same number is possible because my PRI connecting to these routers is a hunting number (same service provider). So I want the spoke sites to dial R1 first and if the router or the line is not available I want it to go to R3.

My interesting traffic is 'IP'.

Using a second number (another data center) is a better design, however, since our secondary data center is in a different region it is not cost effective.


thanks,

Arana


Richard Burts Thu, 02/21/2008 - 15:02
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Arana


Perhaps there is some aspect that I am not understanding properly. But if you dial a number and it does not work then why would you dial it again and assume that it would work?


I support several routers with ISDN connections that are in a hunt group. The way that our hunt group works is that if the ISDN switch attempts to send a call to router1 and it does not accept the call then the hunt group automatically sends the call to router2. The other device does not need to call twice to get to the second router. Does your hunt group work in a different way?


HTH


Rick

rana_beech Thu, 02/21/2008 - 15:24
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Rick,


yes. It works exactly like what you have discusses in your post, except that I am a bit confused with the command. Since the dial map command has IP and name included, i am assuming that the IP and the name will be different. SInce I am dialing into another router now for the seconda call (R3 in this case), the IP address and name will be different but the dial number will be the same.

Perhaps you can post the config of similar config senario and I can see the picture clearly.


Thanks,

Arana

dongdongliu Fri, 02/22/2008 - 23:43
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hi Richard,


do you think of "dialer watch" is a good way? please help to check this, thank you.


int dialer 0

ip add 203.117.12.X 255.255.255.0

encapsulation ppp

dialer-map ip 203.117.12.7 broadcast name R1 1234567890

dialer pool 1

dialer-group ...


int dialer 1

ip add 203.117.25.X 255.255.255.0

encapsulation ppp

dialer-map ip 203.117.25.19 broadcast name R3 1234567890

dialer pool 2

dialer watch-group 5

dialer-group 2 ...

dialer watch-list 5 delay route-check initial 60 ip 203.117.12.7 XXX.XXX.XXX.XXX


int bri 0/0

enc ppp

dialer pool-member 1

dialer pool-member 2

...


if the first dial will work well, the route 203.117.12.7 will appears in the route table, dialer watch will do nothing.

if the first dial fail, route 203.117.12.7 will be removed from route table, the second dial will call peer number.


please give me your opinion


thanks

dongdong


Richard Burts Sat, 02/23/2008 - 08:29
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As this discussion started I believed that the question was how to get the router to dial an alternate number if the first number did not work. And the answer to that is fairly simple - you add a second dialer map with the second number.


But Arana says that the question is really not about dialing a second number but it is about dialing a second router. For that a second dialer map in the same dialer interface may not be the best solution. I believe that the suggestion from dongdong about configuring 2 dialer interfaces may be the better way to go. Whether to use something like floating static routes or to use dialer watch is something that Arana will need to determine.


HTH


Rick

Richard Burts Sat, 02/23/2008 - 08:42
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I have been thinking some more about this and believe that there may be another possibility to consider. If the site that Arana is dialing to (the R1 and R3) is using a hunt number then it should connect to the second router if the first router does not accept the call. The main difficulty with this would become the ppp authentication. If the call might connect to different remote routers how do you set up the authentication? The advantage of 2 dialer interfaces is that each dialer interface would have its own dialer map with its own remote router ID and authentication becomes straightforward. But there is the possibility to configure a single dialer interface and to configure remote router and local router ID (especially if R1 and R3 were configured to use the same local name) so that you could authenticate to either of the routers on a single call. This way the router has a single dialer interface and a single dialer map. The router makes a call and the hunt number sends the call to R1 or to R3 and the router can authenticate with either of them. This might be a good solution.


HTH


Rick

dongdongliu Sat, 02/23/2008 - 20:11
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hi Richard,


thanks again, your post always bring me knowledge.


regards

dongdong

rana_beech Sun, 02/24/2008 - 14:36
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Hi Rick,


Thank you for the suggestions on my post. In the next two days I will try and see what would be the best possible solution.


Once last question - if I have 2 dialer interface do I need to configure priority? How does the dailing router know which router to call first?


Arana.

Richard Burts Sun, 02/24/2008 - 18:00
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Arana


There are probably a couple of issues to address about this.


First let us clarify that if you have 2 dialer interfaces and they both dial the same number then you do not control which router you are dialing to but the hunt number determines which router you will connect to.


Second let us be clear that when you have 2 dialer interfaces (and each interface has different IP addressing) that the router chooses which dialer interface to use based on what is the destination address of some packet that you are attempting to forward. You have not yet explained to us what traffic will be sent to the dialer interfaces. Perhaps you can clarify that item for us?


Third, the more I think about it the more important it becomes that if you have a hunt number that you are dialing and if it is controlled by the hunt number which router you will connect to, then it becomes more important that all the remote routers included in the hunt number should authenticate using the same ID.


And based on this I believe that there is no need for you to configure priority since you have no control over which remote router you will connect to.


HTH


Rick

rana_beech Mon, 02/25/2008 - 06:23
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H Rick,


Thanks. The interesting traffic here will be IP traffic. I can have a window of maintenence in a few weeks time and I shall test the hunting scenario with various options.

I appreciate and would like to thank you for taking the time to go over my case.


Thanks,

Arana

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