Tài liệu giảng dạy CCNA - module 06 chapter 20-Point-to-Point Leased Line Implementation

Module 06 WAN Technology Chapter 20 Point-to-Point Leased Line Implementation Table of Content Review of WAN Basics Data-Link Protocols for Point-to-Point Leased Lines Authentication Over WAN Links Review of WAN Basics Overview of WAN  The three main categories of WAN options:  Leased point-to-point lines  Dial lines (also called circuit-switched lines)  Packet-switched networks Physical Components of Point-to-Point Leased Lines TELCO CSU CSU WAN switch CPE CO Demarc CPE WAN switch CO Demarc Data-Link Protocols for Point-toPoint Leased Lines The important comparison points between HDLC and PPP Protocol Error Correction Architecte Type Field Other Attributes HDLC No No HDLC serves as Cisco’s default on serial links Cisco uses a Proprietary Type field to support multiprotocol traffic Supports synchronous links only PPP Support but not enabled by default Yes PPP was meant for multiprotocol interoperability from its inception, unlike HDLC PPP also supports asynchronous communication Configuring HDLC/PPP Encapsulation  Enter the interface configuration mode of the serial interface  Then enter the encapsulation hdlc command to specify the encapsulation protocol on the interface  When communicating with a non-Cisco device, synchronous PPP is a more viable option PPP-Specific Features     Error detection Looped link detection Multilink support Authentication Looped Link Detection  LCP notices looped links quickly using a feature called magic numbers When using PPP, the router sends PPP LCP messages instead of Cisco-proprietary keepalives across the link; these messages include a magic number, which is different on each router If a line is looped, the router receives an LCP message with its own magic number instead of getting a message with the other router’s magic number Enhanced Error Detection  PPP LCP analyzes the error rates on a link using a PPP feature called Link Quality Monitoring (LQM) LCP at each end of the link sends messages describing the number of correctly received packets and bytes The router that sent the packets compares this number to the number of packets and bytes it sent, and it calculates percentage loss The router can be configured to take down the link after a configured error rate has been exceeded  The only time this feature helps is when you have redundant routes in the network By taking down a link that has many errors, you can cause packets to use an alternative path that might not have as many errors 3 Authentication Over WAN Links PPP Authentication Protocols:PAP PPP Authentication Protocols:CHAP CHAP is used at the startup of a link and periodically verifies the identity of the remote node using a three-way handshake PPP Authentication Protocols:CHAP Operation Sydney Hongkong Challenge Sydney Username Hongkong Melbourne Random ID 01 Password cisco sanhinoon MD5 Username Sysney Melbourne MD5 Hash # Response Hash # Hongkong Hash# ID 02 Sydney Ack/Nack ID 03 Is Equal? Password cisco sanhinoon PPP Encapsulation And Authentication Process Configuring PPP authentication  Step 1: Define username and password to expect from remote router  Router(config)#username remote password secret  Secret must be the same at both ends  Step 2: Enable PPP  Router(config-if) encapsulation ppp  Step 3: Configure authentication  Router(config-if) Ppp authentication { pap|chap|papchap|chap-pap}  Step 4: if IOS 11.1 or later, PAP must be enable on interface  Router(config-if)ppp pap sent-username user password pass Configuring PPP authentication: PAP Configure PPP authentication: CHAP Summary  HDLC & PPP  PAP & CHAP ... Data-Link Protocols for Point-to-Point Leased Lines Authentication Over WAN Links Review of WAN Basics Overview of WAN  The three main categories of WAN options:  Leased point-to-point lines... Dial lines (also called circuit-switched lines)  Packet-switched networks Physical Components of Point-to-Point Leased Lines TELCO CSU CSU WAN switch CPE CO Demarc CPE WAN switch CO Demarc Data-Link... CSU CSU WAN switch CPE CO Demarc CPE WAN switch CO Demarc Data-Link Protocols for Point-toPoint Leased Lines The important comparison points between HDLC and PPP Protocol Error Correction Architecte