Configuring Serial Point to Point Encapsulation

© 2002, Cisco Systems, Inc. All rights reserved.
© 2002, Cisco Systems, Inc. All rights reserved.
2
Configuring Serial
Point-to-Point Encapsulation
Objectives
Upon completing this lesson, you will be able to:
Use Cisco IOS commands to configure serial interfaces using HDLC and PPP encapsulation for leased-line connections, given a functioning router
Use show commands to identify anomalies in HDLC and PPP encapsulation for leased-line connections, given an operational router
Use debug commands to identify events and anomalies in PPP configuration for leased-line connections, given an operational router
Supports only single-protocol environments
HDLC Frame Format
Uses a proprietary data field to support
multiprotocol environments
Router(config-if)#encapsulation hdlc
Enables HDLC encapsulation
Uses the default encapsulation on synchronous serial interfaces
Configuring HDLC Encapsulation
PPP can carry packets from several protocol suites
using NCP.
PPP controls the setup of several link options using LCP.
An Overview of PPP
Layering PPP Elements
PPP: A data link with network layer services
PPP LCP Configuration Options
PPP Session Establishment
Two PPP authentication protocols:
PAP and CHAP
Passwords sent in clear text
Peer in control of attempts
PPP Authentication Protocols
Hash values, not actual passwords, are sent across link.
The local router or external server is in control of attempts.
Challenge Handshake Authentication Protocol
Configuring PPP and Authentication Overview
Router(config-if)#encapsulation ppp
Enables PPP encapsulation
Configuring PPP
Router(config)#hostname name
Assigns a host name to your router
Router(config)#username name password password
Identifies the username and password of remote router
Configuring PPP
Authentication
Router(config-if)#ppp authentication
{chap | chap pap | pap chap | pap}
Enables PAP and/or CHAP authentication
Configuring PPP
Authentication (Cont.)
CHAP Configuration Example
Router#show interface s0
Serial0 is up, line protocol is up
Hardware is HD64570
Internet address is 10.140.1.2/24
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation PPP, loopback not set, keepalive set (10 sec)
LCP Open
Open: IPCP, CDPCP
Last input 00:00:05, output 00:00:05, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
38021 packets input, 5656110 bytes, 0 no buffer
Received 23488 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
38097 packets output, 2135697 bytes, 0 underruns
0 output errors, 0 collisions, 6045 interface resets
0 output buffer failures, 0 output buffers swapped out
482 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up



Verifying the HDLC and PPP Encapsulation Configuration
debug ppp authentication shows successful CHAP output.
Verifying PPP Authentication
Summary
HDLC is the Cisco default data-link layer protocol for encapsulating data on synchronous serial data links.
PPP encapsulates network layer protocol information over point-to-point links.
Configurable aspects of PPP include methods of authentication, compression, and error detection, as well as whether or not multilink is supported.
PPP session establishment progresses through three phases: link establishment, authentication, and network layer protocol.
Summary (Cont.)
When configuring PPP authentication, you can select PAP or CHAP. In general, CHAP is the preferred protocol.
You enable PPP with the encapsulation ppp command and PPP authentication with the ppp authentication command.
Use the show interface command to verify proper configuration of PPP encapsulation.
The debug ppp authentication command displays the authentication exchange sequence.