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Showing posts with label PPPoE. Show all posts
Showing posts with label PPPoE. Show all posts

Monday, May 16, 2011

PPPoE Configurations - Maipu and Cisco

In last post we saw, PPPoE theory, In this post we will see Maipu and Cisco router configurations for PPPoE.
Maipu Basic Commands for Configuring -PPPoE
Configuration Mode
pppoe enable
Enable PPPoE server.
pppoe-client dial-pool-number number
Configure PPPoE client.
pppoe-client auto-dial always
*Configure the auto dialing of the PPPoE client
pppoe-client auto-dial time-range string
*Configure PPPoE client to perform the automatic dialing according to the set time
vpdn enable
*Enable VPDN.
vpdn-group number
Configure VPDN group
*Configure VPDN as accepting dial-in
protocol pppoe
*Configure the application protocol over VPDN
pppoe limit per-mac number
*Configure the maximum connection number of the same mac address at PPPoE client
virtual-template number
*Configure the template number used when VPDN accepting dial-in
local name host-name
Configure VPDN  device name

PPPoE Normal Configuration - Maipu

Configuration instance 1
Description -

As shown in the above figure, PPPoE client (Router-a) sets up the PPPoE connection with the PPPoE server via the Ethernet interface.

The configuration of Router-a:
Router (config)#dialer-list 1 protocol ip permit
Configure the data type of triggering dialer
Router (config)#interface dialer0
Configure dialer interface
Router (config-if-dialer0)#ip address negotiated
Configure IP address
Router (config-if-dialer0)# encapsulation ppp
Encapsulate the PPP protocol.
Router (config-if-dialer0)#dialer in-band
Enable DDR dialer
Router (config-if-dialer0)#dialer-group 1
Reference triggering list
Router (config-if-dialer0)#dialer pool 1
Configure dialer pool
Router (config-if-dialer0)#exit
Exit interface
Router (config)#interface fastethernet0
Enter into Ethernet interface
Router (config-if-fastethernet0)# pppoe-client dial-pool-number 1
Configure PPPoE client and put F0 interface into dialer group 1
Router (config-if-fastethernet0)#exit
Exit interface
Router (config )#ip route dialer0
Configure the default route

The configuration of Router-b:
Router(config)#int loopback 0
Configure loopback 0
Router(config-if-loopback0)#ip address
Configure the IP address of the loopback port

router(config)# ip local pool pppoe-pool
Configure address pool
Router (config)#int virtual-template 1
Configure PPPoE virtual template interface
Router (config-if-virtual-template1)#ip unnumber loopback0
Configure the IP address of the interface. It is recommended to use the ip unnumber command. Configure IP address directly for virtual template. The load balance results in the PPPOE server can only enable the sixth valid connection.
Router (config-if-virtual-template1)#encapsulation ppp
Encapsulate the PPP protocol
Router (config-if-virtual-template1)#peer default ip address pool pppoe-pool
The address pool adopted when distributing the IP address to the client
Router (config-if-virtual-template1)#exit

Router (config)#vpdn enable
Enable VPDN virtual tunnel
Router (config)#vpdn-group 1
Create virtual channel group
Router (config-vpdn)# pppoe limit per-mac 2
The same mac of the client is allowed to create two PPPoE connections.
Router (config-vpdn)#local name pppoe-server
The command is used to configure ac-name on the Ethernet interface when configuring the PPPoE client
Router (config-vpdn)#accept-dialin
Configure VPDN as accepting dialin
Router (config-vpdn-acc-in)#protocol pppoe
Specify the application protocol over VPDN
Router (config-vpdn-acc-in)#virtual-template 1
Specify the virtual template interface number used during the PPPoE  session
Router (config-vpdn-acc-in)#exit

Router (config-vpdn)#exit

Router (config)#interface fastethernet0
Configure fastethernet0 as the PPPoE server port
Router (config-if-fastethernet0)#pppoe enable
Enable the PPPoE protocol
Router (config-if-fastethernet0)#exit

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PPPoE Theory

In today section, We will discuss about PPPoE theory part …. PPPoE protocol majorly used in broadband sector for connecting end users to ISP for accessing internet.

There are three technologies which are used in Broadband industry to connect users to ISP network to access internet, These are - PPPoE , IPoE and PPPoA. But here I will discuss PPPoE and IPoE.


Point-to-Point Protocol over Ethernet (PPPoE) relies on two widely accepted standards: PPP and Ethernet. PPPoE is a specification for connecting the users on an Ethernet to the Internet through a common broadband medium, such as a single DSL line, wireless device or cable modem. All the users over the Ethernet share a common connection, so the Ethernet principles supporting multiple users in a LAN combine with the principles of PPP, which apply to serial connections

PPPOE stages-

Traditionally PPP connections are established between two end points over a serial link.All PPP frames sent on the wire are sure to reach the other end. But Ethernet networks are multi-access where each node in the network can access every other node. An Ethernet frame contains the hardware address of the destination node .This helps the frame reach the intended destination.

                Hence before exchanging PPP control packets to establish the connection over Ethernet, the MAC address of the two end points should be known to each other so that they can be encoded in these control packets. The PPPoE Discovery stage does exactly this. In addition it also helps establish a Session ID that can be used for further exchange of packets.

             PPP is a peer-to-peer protocol, PPPoE is inherently a client-server relationship ,multiple hosts can connect to a ISP over  single physical connection.
The Discovery process consists of four steps –

Client to server: Initiation (PADI) – 1st step

PADI stands for PPPoE Active Discovery Initiation 

If a user wants to dial up to the Internet using DSL, then his computer first must find the DSL Access Concentrator at the user nearest POP. Communication over Ethernet is only possible via MAC addresses.

 As the computer does not know the MAC address of the DSL Access concentrator, it sends out a PADI packet via an Ethernet broadcast . This PADI packet contains the MAC address of the computer sending it.

Server to client: Offer (PADO) – 2nd step

PADO stands for PPPoE Active Discovery Offer 

Once the user's computer/device has sent the PADI packet, the DSL-Access concentrator replies with a PADO packet, using the MAC address supplied in the PADI. The PADO packet contains the MAC address of the DSL-AC. If more than one POP's DSL-AC replies with a PADO packet, the user's computer selects the DSL-AC for a particular POP using the supplied name or service.

Client to server: Request (PADR) – 3rd step

PADR stands for PPPoE Active Discovery Request 

A PADR packet is sent by the user's computer to the DSL-AC following receipt of an acceptable PADO packet from the DSL-AC. It confirms acceptance of the offer of a PPPoE connection made by the DSL-AC issuing the PADO packet.

Server to client: Session-confirmation (PADS) – 4th step

PADS stands for PPPoE Active Discovery Session-confirmation

The PADR packet above is confirmed by the DSL-AC with a PADS packet, and a Session ID is given out with it. The connection with the DSL-AC for that POP has now been fully established.

After this process to PPP session starts -

PPP was designed to support switched connections such as dial-in users, it is well-suited to support individual subscribers. 
  • First, the link connection is established using Link Control Protocol (LCP). 
  • Second, the subscriber is authenticated as part of the connection establishment. 
  • Third, a Network Control Protocol (NCP) establishes the protocol parameters used for communications . 
  • Internet Protocol Control Protocol (IPCP) is the NCP used to establish an IP connection over the established link, including assigning an IP address to the client. 
  • At this point the subscriber can access the network, and PPP includes a means of monitoring link quality and availability.

Below diagram provides an overview of PPPoE session establishment. Although the entire lifecycle is depicted, the always-on broadband connections are rarely terminated normally.

For PPPoE connections. We can use Routers also. We can do NAT  and serve our internal network. In PC PPPoE client software is used for dial up.
In upcoming posts we will see the PPPOE configuration for routers. 
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