Ccna routing and Switching Complete Study Guide

show int Multilink1

Multilink1 is up, line protocol is up

  Hardware is multilink group interface

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Point-to-Point Protocol (PPP) 

911

  Internet address is 10.1.1.1/24

  MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,

     reliability 255/255, txload 1/255, rxload 1/255

Encapsulation PPP, LCP Open, multilink Open

Open: IPCP, CDPCP, loopback not set

 Keepalive set (10 sec)

[output cut]

Let’s move on to configure a PPPoE client on a Cisco router.

PPP Client (PPPoE)

Used with ADSL services, PPPoE (Point-to-Point Protocol over Ethernet) encapsulates PPP 

frames in Ethernet frames and uses common PPP features like authentication, encryption, 

and compression. But as I said earlier, it can be trouble. This is especially true if you’ve got 

a badly configured firewall!

Basically, PPPoE is a tunneling protocol that layers IP and other protocols running 

over PPP with the attributes of a PPP link. This is done so protocols can then be used to 

contact other Ethernet devices and initiate a point-to-point connection to transport IP 

packets.

Figure 21.19 displays typical usage of PPPoE over ADSL. As you can see, a PPP session 

is connected from the PC of the end user to the router. Subsequently, the subscriber PC IP 

address is assigned by the router via IPCP.

f i g u r e   21.19     PPPoE with ADSL

CPE

(bridging)

DSLAM

ATM

Aggregation

router

ISP/Corp

router

AAA

OC3

ATM

IP

Your ISP will typically provide you with a DSL line and this will act as a bridge if 

your line doesn’t provide enhanced features. This means only one host will connect 

using PPPoE. By using a Cisco router, you can run the PPPoE client IOS feature which 

will connect multiple PCs on the Ethernet segment that is connected to the router.

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Chapter 21 

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  Wide Area Networks