Point-to-Point WANs

Point-to-Point WANs

1. HDLC

   • Cisco added a field to the ISO standard HDLC protocol (Type field)
   • Configuration of HDLC: 1-Use the ip address address mask command in interface configuration mode to configure the interface IP address. 2-The following tasks are required only when the specifically listed conditions are true: A. If an encapsulation protocol interface subcommand already exists, for a non-HDLC protocol, use the encapsulation hdlc command in interface configuration mode to enable HDLC. Alternatively, use the no encapsulation protocol command in interface configuration mode to use the default setting of HDLC as the data link protocol. B. If the interface line status is administratively down, use the no shutdown command in interface configuration mode to enable the interface. C. If the serial link is a back-to-back serial link in a lab, use the clock rate speed command in interface configuration mode to configure the clocking rate. Use this command only on the one router with the DCE cable (per the show controllers serial number command). 3- The following steps are always optional and have no impact on whether the link works and passes IP traffic: A. Use the bandwith speed-in-kbps command in interface configuration mode to configure the link's documented speed so that it matches the actual clock rate of the link. B. For documentation purposes, use the description text command in interface configuration mode to configure a description of the purpose of the interface.

2. PPP

   • PPP provides several basic but important functions that are useful on a leased line that connects two devices: -Definition of a header and trailer that allows delivery of a data frame over the link. -Support for both synchronous and asynchronous links. -A protocol Type field in the header, allowing multiple Layer 3 protocols to pass over the same link. -Built-in authetication tools: Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). -Control protocols for each higher-layer protocol that rides over PPP, allowing easier integration and support of those protocols.
   • encapsulation ppp
   • Link Control Protocol (LCP)
     • This one protocol has several different individual functions, each focused on the data link itself, ignoring the Layer 3 protocol sent across the link.
     • PPP LCP Features Function/LCP Feature/Description Looped link detection/Magin number/Detects whether the link is looped, and disables the interface, allowing rerouting over a working route Error detection/Link-quality monitoring (LQM)/Disables an interface that exceeds an error percentage threshold, allowing rerouting over better routes Multilink support/Multilink PPP/ Load balances traffic over multiple parallel links Authentication/PAP and CHAP/Exchanges names and passwords so that each device ca verify the identity of the device on the other end of the link
   • Network Control Protocols (NCP)
     • This is a category of protocols, one per network layer protocol. Each protocol performs functions specific to its related Layer 3 protocol.
     • IPCP
       • for IPv4
     • IPv6CP
       • for IPv6
     • CDPCP
       • for CDP
   • PAP
     • To configure PPP along with PAP on an interface that has all default configuration on the serial interfaces of both routers, follow these steps: 1-Use the encapsulation ppp command in interface configuration mode, on the serial interface on both routers, to enable PPP on the interfaces. 2-Define the usernames and passwords used by the two routers: A. Use the username name password password command in global configuration mode on each router, to define the name (case-sensitive) used by the neighboring router, and the matching password (case-sensitive). 3- Use the ppp authentication pap command in interface configuration mode on each router to enable CHAP on each interface. 4-Use the ppp pap sent-username name password password interface configuration command. (The name and passwords should match the name in the neighboring router's username password command).
   • CHAP
     • To configure PPP along with CHAP on an interface that has all default configuration on the serial interfaces of both routers, follow these steps: 1-Use the encapsulation ppp command in interface configuration mode, on the serial interface on both routers, to enable PPP on the interfaces. 2-Define the usernames and passwords used by the two routers: A. Use the hostname name command in global configuration mode on each router, to set the local router's name to use when authenticating. B. Use the username name password password command in global configuration mode on each router, to define the name (case-sensitive) used by the neighboring router, and the matching password (case-sensitive). (The name in the username command should match the name in the neighboring router's hostname command). 3- Use the ppp authentication chap command in interface configuration mode on each router to enable CHAP on each interface.
   • Multilink PPP
     • Configuring MLPPP: 1-Configure matching multilink interfaces on the two routers, configuring the interface subcommands for all Layer 3 features (IPv4, IPv6, and routing protocol) under the multilink interfaces (and not on the serial interfaces). 2-Configure the serial interface with all Layer 1 and 2 commands, like clock rate (Layer 1) and ppp authentication (Layer 2). 3-Configure some PPP commands on both the multilink and serial interfaces, to both enable MLPPP and associate the multilink interface with the serial interfaces.
     • Example: interface multilink 1 encapsulation ppp ip address adress mask ppp multilink group 1 Interface Serial 0/0/0 encapsulation ppp ppp multilink no ip address ppp multilink group 1 !Authentication goes here