TAILIEUCHUNG - CCNA 1 and 2 Companion Guide, Revised (Cisco Networking Academy Program) part 13

Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 13 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | Page 89 Tuesday May 20 2003 2 53 PM Networking Models 89 Figure 2-32 Optical Platform The Cisco ONS 15454 DWDM Optical Network System Security Devices Because of increased Internet and extranet connections as well as more telecommuters and mobile users accessing enterprise networks from remote sites the importance of network security increases. Firewalls AAA servers and VPN concentrators are components or devices related to network security. Firewalls The term firewall refers to either a firewall program running on a router or server or a special standalone hardware component of a network. A firewall protects a private network s resources from users in other networks. Working closely with a router program a firewall examines each network packet to determine whether to forward it to its destination. Using a firewall is like using a traffic officer to ensure that only valid traffic can enter or leave certain networks. Figure 2-33 shows a Cisco PIX Firewall 535 series which is a dedicated network device. Page 90 Tuesday May 20 2003 2 53 PM 90 Chapter 2 Networking Fundamentals Figure 2-33 Cisco PIX Firewall AAA Servers An AAA server is a server program that handles user requests for access to computer and network resources. An AAA server provides authentication authorization and accounting services for an enterprise. The AAA server ensures that only authentic users can get into the network authentication that the users are allowed access only to the resources they need authorization and that records are kept of everything they do after they are allowed entry accounting . An AAA server is like the credit card system. To put charges on a credit card the merchant must verify that the credit card actually belongs to the person using it authentication . The merchant must also check that the credit card has enough credit left for the requested charge amount authorization and then the merchant must record the charge to the user s account accounting . .

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