ADSL with cisco 871

Answered Question
Aug 16th, 2009


our customer has a branch office that should be connected to central place via VPN site-to-site connection.

In branch is in use ADSL line via ethernet cable with name and password authentication again ISP network. For connection will be used a cisco 871 router in branch with two ethernet interfaces (LAN/WAN).

in central is ASA for VPN termination.

How to configure this router to work with ADSL circuit and what type of VPN to use? (maybe a PPPoE protocol...)

Can someone help how to configure this via CLI?

Many thanks.

I have this problem too.
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Correct Answer by Paolo Bevilacqua about 7 years 1 month ago

Not necessary.

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Overall Rating: 3 (1 ratings)
Paolo Bevilacqua Sun, 08/16/2009 - 13:24

Hi, take no offense but it seems to me you have no experience whatsoever in configuring routers and VPN solutions.

If you try that yourself no doubt you will get some result eventually, but it may cost you a lot of time and frustration.

My recommendation would be that you hire a reputable professional for the job.

lubosbella Mon, 08/17/2009 - 04:54

Ok, no problem im not a cisco imagine that we are in testing environment....

Im going to do PPPoE against ISP. I used SDM (version 2.5) and it give me this set of command:

interface Vlan1

ip tcp adjust-mss 1412


interface FastEthernet4

pppoe-client dial-pool-number 2

pppoe enable


interface Dialer1


default interface Dialer1

interface Dialer1

ip mtu 1452

no shutdown

ip address

dialer pool 2

dialer-group 1

encapsulation ppp

dialer idle-timeout 120

dialer fast-idle 20

ppp authentication chap pap callin

ppp pap sent-username jeff password 0 *****

ppp chap hostname jeff

ppp chap password 0 *****


dialer-list 1 protocol ip permit


But my router stops on pppoe enable commnad with output: % Invalid input detected at '^' marker. So it is not know this command....i dont know why? - maybe needed only in older IOS...


If i try to set PPPoE step-by-step using this guide then my router don`t know command protocol pppoe in vpdn enable--request dialin--(there is only protocol L2TP command)....

my IOS: Cisco IOS Software, C870 Software (C870-ADVIPSERVICESK9-M), Version 12.4(15)T7, RELEASE SOFTWARE (fc3)

So im doing a mistake or i cant use this command in this IOS version?...

Problem is that i cant verify if my config is real working for now because i have not a dsl line with im looking for good preparation.


Paolo Bevilacqua Mon, 08/17/2009 - 08:09

The guides are sometime outdated and wrong.

If you use the SDM it will also make a lot of errors. For example the correct ip mtu on dialer1 should be 1492, not 1452. And 1452 as for adjust-mss. The rest seems fine.

lubosbella Mon, 08/17/2009 - 08:39


i corrected it to good values. So commands "pppoe enable" in fastethernet interface or "request dialin-->protocol pppoe" are probably not necessary with this vesion of IOS? (i cant type it and SDM write error)


Correct Answer
Paolo Bevilacqua Mon, 08/17/2009 - 09:34

Not necessary.

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