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Cisco Router with external ADSL Modem

Hi Guys,

I'm new to Cisco...and need help with configuring my new Cisco 881 Router with my existing ADSL modem.

At the moment, i am connecting to the internet using tp-link modem router, all PPPoE/DHCP/Wireless is set up there...and that connect to the switch where all my computer connected to.

Now i want to connect this new Cisco Router to it to basically do the firewall/filtering/dhcp...leave the authentication thing on my Modem.

Can i get a head start what to configure here on the cisco? since it does not work as easily as other Router where I can just plug a cable from modem LAN to Router LAN..

Much appreciated with the help!


Hall of Fame Master

A cisco router used as you said is wasted and useless.

You should instead set the modem in bridge mode, and let the router do the router. There are many threads on the subject.

Anyway an enterprise-class Cisco router is not apt as home or user-friendly device so unless you are prepare to sped a lot of time studying and trying, and receive much aggravation, maye it's better that you gave up on it.


Hello Paolo,

i need to do the same thing, connect a 876 Cisco router with an existing ADSL modem. The reason is that the router itself cannot synchronize with the DSL line due to very bad condition of the telephone lines.

We found a modem that is probably more 'sensitive' and  can synchronize, so i would like to connect it with the Cisco router.

I have read somewhere that i have to connect the modem to the console or AUX port of the cisco router using a rollover modem cable. Is that true? Can i connect the two devices through ethernet, and how?

I need the authentication done by the router.

Can you please help with the configuration? I have some experience with cisco router configuration.

Thank you in advance