cisco ccna glossary

cisco ccna glossary.PPP should be used in a multi-vendor environment. know the services that PPP provides: authentication via CHAP and PAP, support for multiple encapsulated protocols, compression, multiple links, error detection/correction, support for synchronous and asynchronous circuits. Be able to describe the role that LCP and NCP play in PPP and the differences between PAP and CHAP authentication. As with HDLC, know how to troubleshoot PPP connections: use the command show interfaces to view the status of LCPs; use the command show running-config to view the router's configuration to find PAP or CHAP authentication misconfigurations.Virtual Private Networks Currently, VPNs are not the focus of the CCNA exam, but you may encounter questions about the following: when VPNs are highly recommended. the various VPNs offered by Cisco. basic VPN terminology such as IPSec. Generic Routing Encapsulation Tunnel Unicast A GRE point-to-point tunnel is a logical connection between two routers that is used to carry a variety of IP and non-IP traffic ° It is stateless: no traffic control or acknowledgement mechanisms are provided and no security mechanisms are provided. When configuring a GRE tunnel, the commands tunnel source and tunnel destination are essential, and a Layer 3 address belonging to the same subnet must also be assigned.24.6 Authentication SummaryA CPE is a WAN device that is owned by the customer; a demarcation point is the end of the carrier's responsibility for its circuit; and a local loop is a connection from the demarcation point to the carrier's WAN switching equipment. WAN connections fall into four main categories. Leased lines use dedicated circuits and are suitable for situations where the connection distance is short, traffic needs to be carried constantly, and guaranteed bandwidth is required. Circuit-switched connections provide analog modems and dial-up functionality needed for ISDN; these connections are used primarily as backup connections and to increase bandwidth. Packet-switched connections, including Frame Relay and X.25, are used to connect multiple sites at a reasonable cost; if guaranteed bandwidth or support for multiple services is required, element-switched services such as ATM are a better solution.Cisco synchronous serial interfaces support DB-60 and DB.26 connectors, and the default encapsulation for these interfaces is Cisco HDLC; Cisco HDLC and ISO HDLC are not compatible with each other. To change the encapsulation of an interface to Cisco HDLC, use the command encapsulation hdlc; to view the data link layer encapsulation of a serial interface, use the command show interfacesoChapter 24 Introduction to WAN 669PPP is one of the most common data link layer encapsulations for serial interfaces, and it is an open standard that defines the following three aspects: frame type, LCP, and NCP. when establishing a PPP connection, LCP is performed first, followed by authentication, and finally NCPoLCP is responsible for negotiating parameters and establishing and maintaining the connection, which includes authentication, compression, link quality, error detection, network layer protocols multiplexing and multilink. The NCP is responsible for negotiating the upper layer protocols that the PPP connection will transport. To set the encapsulation of the serial interface to PPP, use the command encapsulation ppp; to troubleshoot LCP and NCP, use the command debug ppp negotiationoThere are two methods of PPP authentication: PAP and CHAP; PAP sends the password in plaintext over the line, and CHAP sends the hash value calculated by the MD5 hashing algorithm without sending the password over the connection. PAP uses a two handshake process, while CHAP uses a three-handshake process. Authentication is optional, but to configure it, use the interface subconfiguration mode command ppp authentication {chap | pap | ms-chap}o To create a local authentication table containing the username and password, use the command usernameo To troubleshoot authentication, use the command debug ppp authenticationoVPNs are an increasingly popular and inexpensive solution for providing secure connections over public networks. VPN types include site-to-site and remote access; the most common VPN implementations are IPSec and SSL. o Cisco remote access VPNs include Easy VPN using IPSec and WebVPN using SSL. o Easy VPN contains two components: a server and a remote end; where the server centrally stores the policy configuration. Cisco supports both hardware remote ends and software remote ends. IPSec is an open standard on how to implement site-to-site and remote access VPNs, providing authentication, confidentiality, integrity, and anti-replay protection. The protocols used to implement IPSec include ISAKMP, IKE, DH, AH, and ESP.GRE, which is used to connect disparate networks through an intermediate network, does not provide any security mechanism, so for GRE tunnels that traverse the public network, another protocol, such as IPSec, is typically used for protection. To create a GRE tunnel interface, use the following commands: interface tunnel, tunnel source, and tunnel destination. when transmitting IP traffic over a GRE tunnel, both ends of the tunnel must assign unique IP addresses to their tunnel interfaces, and both IP addresses must belong to the same subnet.