isdn still active

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Aug 26th, 2007
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Dear all,

when i just configured the isdn from the branch side and the dialer from the PRI line, it is automaticlly come up even the primary link is still up.

i check the intersting traffic which i exclude the eigrp routing protocol form it.

when i check the routing entry, i found some intry prefer isdn over the serial so i increase the delay at the bri link, so all routing change to the primary link ( serial)

you now that i can't stay the isdn active it is money so what do you suggest me to do ?


Ahmad abu zayyad

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jay77jay77 Sun, 08/26/2007 - 18:26
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One option is to use the "backup interface dialer x" at the branch office router.

This will bring down the dialer when the primary interface is active.


jay77jay77 Sun, 08/26/2007 - 18:27
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Appreciate if you could post the config for further help

Richard Burts Sun, 08/26/2007 - 18:37
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Assuming that you have not disabled the inactivity timer then if the ISDN is still staying connected then there is still some "interesting" traffic. You need to identify the interesting traffic and do something about it.

If you have problems figuring out what the interesting traffic is then running debug dialer may be helpful.

As the previous posteer points out it might be helpful if you post the configs.



jay77jay77 Sun, 08/26/2007 - 19:01
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hi Rburts,

In a similar case of mine, everything works fine as per the access list configured, whenever a traffic is initiated from the LAN.

But when i do a tracert from the router itself, when primary link is active. I noticed that isdn is also fired out. A debug dialer showed the cause S=primary link ip address and D=

Is this normal. As in practice nobody will be doing the tracert from the router so often.

Any suggestion?


Richard Burts Mon, 08/27/2007 - 05:59
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I would think that it is unusual for a tracert to send out broadcast packets (which seems to be what your show dialer is indicating). Perhaps if you post the output of the tracert and post the output of show ip route from the router we might be able to figure what is going on.



ahmadabuzayyad Mon, 08/27/2007 - 23:41
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dear all,

i don't think it is relate to the broadcast, since i do additiona testing which is as follow:

i make the dial only from the head office: isdn stilla active :)

i make the dial from the branch only: the isdn still active :)

i do no cdp enable on both the dialer and bri interface : isdn still active :)

so what do you think is the problem.

if you think it is broadcast, so why the head office dial the branch.

really amazing situation

any new idea or simillar case



smothuku Tue, 08/28/2007 - 03:33
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Hi ,

please paste the config of the router..




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