Глава №1. Резюме

В первой главе рассматриваются сетевые модели, требования и план по внедрению (implementation plans), обозреваются принципы IP маршрутизации. Глава сфокусированна на следующих темах:

• Трафик в конвергентных сетях включает голосовой и видео трафик, трафик голосовых приложений, критически важный трафик, трафик транзакций, протоколов маршрутизации и управляющий трафик.
• Три фазы Cisco IIN: Интеграция транспортной системы (integrated transport), объединение услуг (integrated services), и объединение приложений (integrated applications).
• Три уровня архитектуры SONA: сетевой инфраструктуры (networked infrastructure), интерактивных сервисов (interactive services), прикладной (application).
• Компоненты Cisco Enterprise Architecture для интеграции сети: кампус, ЦОД, удалённые офисы, удалённые сотрудники и WAN.
• Традиционная иерархическая модель сети с тремя уровнями: ядро, уровень распределения и уровень доступа.
• Модель ECNM с тремя функциональными зонами и ассоциированными модулями:
  • Кампус предприятия: Building, Building Distribution, Core, Edge Distribution, Server Farm, Management
  • Граница предприятия: E-commerce, Corporate Internet, VPN and Remote Access, WAN
  • Зона ответственности провайдера услуг: ISP, PSTN, Frame Relay/ATM.
• Два подхода для внесения изменений в сеть: ad hoc и структурный подход.
• Четыре модели, используемые в жизненном цикле ИТ-сервисов: Cisco Lifecycle Services (PPDIOO), ITIL, FCAPS, и TMN.
• Создание плана по внедрению как части фазы проектирования сети, включающего:
  • Информацию о сети;
  • Требуемые инструменты;
  • Требуемые ресурсы;
  • Задачи плана по внедрению;
  • Проверку;
  • Замеры производительности и результаты.

• Network convergence, when routing tables on all routers in the network are synchronized and contain a route to all destination networks. Convergence time is the time it takes for all routers in a network to agree on the new topology. • Static routing characteristics and configuration (using the ip route global configuration command). • Characteristics and configuration (with the router odr global configuration command) of ODR, which uses CDP to carry network information between spoke (stub) routers and the hub router. • Dynamic routing protocol characteristics, including • The metric, a value that routing protocols use to measure paths to a destination. • Configuration, using the router protocol global configuration command. • Distance vector routing, in which all the routers periodically send their routing tables (or a portion of their tables) to only their neighboring routers. • Link-state routing, in which each of the routers sends the state of its own interfaces (its links) to all other routers (or to all routers in a part of the network, known as an area) only when there is a change. • Advanced distance vector routing, in which routers send only changed information when there is a change (similar to link-state protocols) but only to neighboring routers (similar to distance vector protocols). • Classful routing protocol updates, which do not include the subnet mask. Classful protocols (such as RIPv1) do not support VLSM or discontiguous subnets and must automatically summarize across the network boundary to the classful address. • Classless routing protocol updates, which do include the subnet mask. Classless protocols (such as RIPv2, EIGRP, and OSPF) do support VLSM and discontiguous subnets, and do not have to summarize automatically across network boundaries. • RIPv1 and RIPv2 characteristics and configuration, including • The router rip global configuration command to enable RIP • The version {1 | 2} router configuration command to send and receive packets from only one version • The network network-number router configuration command to configure RIP to start up the protocol on interfaces in that network, and send advertisements for the networks connected to the specified interfaces. • The ip rip {send | receive} version {1 | 2 | 1 2} interface configuration command to control the version of RIP on each interface • The no auto-summary router configuration command to turn off automatic summarization • The ip summary-address rip network-number mask interface configuration command to define a network number and mask that meet the particular summarization requirement • The process that Cisco routers use to populate their routing tables: • Valid next-hop IP address— The router first verifies that the route has a valid next-hop IP address. • Metric— If the next hop is valid, the routing protocol chooses the best path to any given destination based on the lowest metric and offers this path to the routing table. • Administrative distance— If more than one route exists for the same network, and with the same prefix from different routing sources, the router decides which route to install based on the administrative distance of the route’s source. The administrative distance is a value between 0 and 255. The lower the administrative distance value, the higher the protocol’s believability or trustworthiness. The route with the lowest administrative distance is installed in the routing table. Routes with higher administrative distances are rejected. • Prefix— The router looks at the prefix being advertised; routes to the same network but with different prefixes can coexist in the routing table. • A comparison of the various IP routing protocols. Multiple protocols may be used within the modules of the Enterprise Composite Network Model. EIGRP and OSPF are the recommended protocols within the Enterprise; BGP is required for inter–autonomous system connectivity on the Internet.