Configuring a Router as a PPPoE Client for DSL Connectivity

Cabling the topology:

1 straight-through cable connecting switch to switch

2 crossover cables between the switches and routers

The basic settings:

Disable DNS lookup "no ip domain-lookup"

Set hostnames "hostname (name)"

encrypt passwords "service password-encryption"

Create a MOTD banner saying "unauthorized access is prohibited"  "banner motd # Unauthorized Access is Prohibited!#"

create passwords for EXEC mode, console, and vty. Then enable login.

set logging synchronous "line con 0" "logging synchronous"

save config "copy running-config startup-config"

I have my routers preconfigured and saved with these settings (minus the passwords) so I typically skip this part. I do set the hostnames to avoid confusion. 

Configuring the ISP router

In global config mode enter the command " username Cust1 password ciscopppoe". This creates a database entry for Cust1 with a password of ciscopppoe. This will allow the Cust1 router to connect with the ISP router using that password later. 

The ISP needs a pool of addresses to hand out to it's DSL customers. Using the command "ip local pool PPPoEPOOL 10.0.0.1 10.0.0.10" creates a range of addresses from 10.0.0.1 to 10.0.0.2 to hand out over PPPoE.

Next we are going to make a Virtual template and connect the F0/1 interface with it. This is done with these commands:

interface virtual-template 1	Creates the Virtual template
ip address 10.0.0.254 255.255.255.0	Assigns it the ip 10.0.0.254/24
mtu 1492	Sets the mtu size to 1492B
peer default ip address pool PPPoEPOOL	Assigns the previously created pool of ip addresses "PPPoEPOOL" to this template
ppp authentication chap callin	Sets the requirement to authenticate using chap to establish a connection.

Now to associate the template to the PPPoE group

bba-group pppoe global	Creates a bba (broadband aggregation) group for PPPoE
virtual-template 1	Assigns virtual-template 1 to the bba group.

Finally link the PPPoE group to the actual f0/1 interface

int f0/1	Moves to int f0/1
pppoe enable group global	Connects the PPPoE group to the interface
no shut	Activates the interface

Configuring the Cust1 router

First configure the f0/1 interface to use PPPoE

int f0/1	Moves to int f0/1
pppoe enable	Enables PPPoE on the interface
pppoe-client dial-pool-number 1	Tells the router is the client and assigns it the dial pool number of 1. The dial pool number corresponds with the dialer interface that will be created next. The dialer and the number assigned here must match to work.

Creating the interface dialer.

int dialer 1	Moves to and creates the dialer interface
mtu 1492	Sets the mtu size to 1492B
ip address negotiated	Tells the interface that the address will be negotiated
encapsulation ppp	Sets the encapsulation to ppp
dialer pool 1	Connects the dialer pool and int f0/1 to the dialer
ppp authentication chap callin	Sets the authentication encryption to chap
ppp chap hostname Cust1	Sets the chap hostname to be used as "Cust1"
ppp chap password ciscopppoe	Sets the chap password to "ciscopppoe"

Set the static default route pointing to dialer 1 and enable some debugging.

ip route 0.0.0.0 0.0.0.0 dialer 1	Sets the static default route to dialer 1
exit	Moves back to privileged mode
debug ppp authentication	Shows PPP events
debug pppoe events	Shows PPPoE events

Lastly enable interface f0/1 with the "no shut" command

To confirm PPPoE is working use "show pppoe session" and "ping 10.0.0.254". there should be an entry in the session table and ping should be successful.

Reflection

Why do ISPs who use DSL, primarily use PPPoE with their customers?

PPPoE allows easy separation of DSL subscribers connections. The means one subscriber cannot see the traffic of another subscriber. PPPoE also allows the ISP to easily track usage by a subscriber. ISP can use deep packet inspection to analyze traffic and limit users connections.