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DDR connects to 3G


I need to configure a C1841-3G router to connect to a 3G gateway.Found a few router configuration examples on the internet,  all using DDR connection.

Why is DDR used for 3G network connection?



Leo Laohoo
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Why is DDR used for 3G network connection?

You mean why is 3G used for DDR?  Probably because it's the cheapest to use 3G than using the traditional ISDN, xDSL, Frame Relay, etc.

Giuseppe Larosa
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Hello Peiwai,

DDR = dial on demand routing

for making a data connection in 3G the 3G modem makes a call, a data call not a voice call, but it is still a call so it is reasonable to use DDR to trigger the 3G connection.

Consider that DDR is a framework used for dial backup using async interface and analog modem or with ISDN B channels and here again a call is made if some conditions are met.

Most of these uses are for backup only.

Be aware that unless you have bought a flat service you need to be very careful in defining interesting traffic in order to avoid to pay very high bills to mobile phone service provider

Hope to help


Thanks Giuseppe.

I have read that DDR is for meant for intermittent connection on WAN, backup purpose.

Therefore I wonder why people normally use DDR for router connection with 3G? Is connection to 3G considered intermittent?

Is there any doc that explains how to configure router C1841-3G-G-SEC to connect 3G?

Also articles that explain how to define interesting traffic to avoid high bills being charged.

Many Thanks


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