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Options: dial backup not using ISDN

This is my first post here. I hope I'm in the right place. I need to provide dial backup to one of our locations but it is too far to run an ISDN circuit to them. Mgt. says too expensive and wants a dial backup solution across a POTS line. The site was just upgraded to VOIP. We only need to allow data traffic.

We have a 2821 router running 12.4(3) version IOS. Not sure what the best option is here. Maybe another alternate way other than a modem and a POTS line. I am just looking for ideas if anyone has them. Thanks

VIP Purple

Re: Options: dial backup not using ISDN


since cost is a concern, you could just use the AUX port (provided the device at the remote location has one) to configure a dial backup solution. This would still involve using a POTS line, but that is probably the cheapest way to get any sort of backup accomplished. Below is a configuration example. Regarding the voice traffic that should not traverse the backup connection, you would need to deny that traffic to trigger the backup, as well as to get across. In order to accomplish this, you would need to configure an access list that denies VoIP traffic, for Cisco, this would typically look like this:

access-list 101 deny tcp any any eq 1720

access-list 101 deny udp any any range 16384 32767

access-list permit ip any any

This access list then would need to be applied to the async interface (based on the configuration example given), as well as to the dialer list that triggers the backup:

interface Async65

ip access-group 101 out


dialer-list 1 protocol ip list 101

Configuring AUX-to-AUX Port Async Backup with Dialer Watch



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