CCNP 1: Building Scalable Cisco Internetworks

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CCNP 1 Building Scalable Cisco Internetworks

• Overview Of Scalable Networks

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The Hierarchical Network Design Model
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Internetworking Design Basics
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Core Layer

• As the center of the network, the core layer is
  designed to be fast and reliable.
• Access lists should be avoided in the core layer
  since they add latency and end users should not
  have access directly to the core.
• In a hierarchical network, end user traffic
  should reach core routers only after those
  packets have passed through the distribution and
  access layers, where access lists may be
  implemented.

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Core Layer (Continued)

• The most powerful Cisco routers serve the core
  because they have the fastest switching
  technologies and the largest capacity for
  physical interfaces.
• The Cisco 7000, 7200, and 7500 series routers are
  modular, allowing interface modules to be added
  providing scalability. The large chassis of this
  series can accommodate dozens of interfaces on
  multiple modules for virtually any media type,
  which makes these routers scalable and reliable
  core solutions.
• Core routers achieve reliability through the use
  of redundant links, usually to all other core
  routers.
• When possible, these redundant links should be
  symmetrical having equal throughput, so that
  equal-cost load balancing may be used.
• Core routers need a relatively large number of
  interfaces to enable this configuration.
• Core routers achieve reliability through
  redundant power supplies and usually feature two
  or more "hot-swappable" power supplies, which may
  be removed and replaced individually without
  shutting down the router.

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Core Layer (Continued)

• With the high-end routers and WAN links involved,
  the core can become a huge expense, even in a
  simple example such as this.
• Some designers will choose not to use symmetrical
  links in the core to reduce cost. In place of
  redundant lines, packet-switched and
  dial-on-demand technologies, such as Frame Relay
  and ISDN, may be used as backup links.
• The trade-off for saving money by using such
  technologies is performance. Using ISDN BRIs as
  backup links can eliminate the capability of
  equal-cost load balancing.

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Core Layer Continued

• The core of a network does not have to exist in
  the WAN. A LAN backbone may also be considered
  part of the core layer.
• Campus networks, or large networks that span an
  office complex or adjacent buildings, might have
  a LAN-based core. Switched Fast Ethernet and
  Gigabit Ethernet are the most common core
  technologies, usually run over fiber.
• Enterprise switches, such as the Catalyst 4000,
  5000, and 6000 series, shoulder the load in LAN
  cores because they switch frames at Layer 2 much
  faster than routers can switch packets at Layer
  3. In fact, as modular devices, these switches
  can be equipped with route switch modules (RSMs),
  adding Layer 3 routing functionality to the
  switch chassis.

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Distribution Layer

• The following rules will protect the core from
  unnecessary or unauthorized traffic.
• Distribution layer routers need fewer interfaces
  and less switching speed than their counterparts
  in the core because they should handle less
  traffic. Nevertheless, a lightning fast core is
  useless if a bottleneck at the distribution layer
  prevents user traffic from accessing core links.
• For this reason, Cisco offers robust, powerful
  distribution routers, such as the 4000, 4500, and
  the 3600 series router. These routers are modular
  allowing interfaces to be added and removed
  depending on need. However, the smaller chassis
  of these series are much more limiting than those
  of the 7000, 7200, and 7500 series.

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Distribution Layer Continued

• Distribution layer routers bring policy to the
  network by using a combination of access lists,
  route summarization, distribution lists, route
  maps, and other rules to define how a router
  should deal with traffic and routing updates

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Distribution Layer Continued

• The figure shows two 3620 routers have been added
  at Core A, in the same wiring closet as the 7507.
  This means that the high-speed LAN links may be
  used to make the connections between the
  distribution routers and the core router.
  Depending on the size of the network, these links
  may be part of the campus backbone and will most
  likely be fiber running 100 or 1000 Mbps.
• In this example, Dist-1 and Dist-2 are part of
  the Core A campus backbone. Dist-1 serves remote
  sites, while Dist-2, serves access routers at
  Site A. If Site A employs VLANs throughout the
  campus, Dist-2 may be responsible for routing
  between them.

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Distribution Layer Continued

• Both Dist-1 and Dist-2 use access lists to
  prevent unwanted traffic from reaching the core.
  In addition, these routers summarize their
  routing tables in updates to Core A, keeping the
  Core A routing table as small and efficient as
  possible

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Access Layer

• Routers at the access layer are deployed to
  permit users at Site A and remote sites Y and Z
  to access the network.
• Access routers generally offer fewer physical
  interfaces than distribution and core routers.
  For this reason, Cisco access routers, which
  include the 1600, 1700, 2500, and 2600 series,
  feature a small, streamlined chassis that may or
  may not support modular interfaces.

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Access Layer Continued

• Each remote site in the example requires only one
  Ethernet interface for the LAN side and one
  serial interface for the WAN side.
• The WAN interface connects by way of Frame Relay
  or ISDN to the distribution router in the wiring
  closet of Site A.
• For this application, the 2610 router provides a
  single 10-Mbps Ethernet port and will work well
  at these locations. These remote sites, Y and Z,
  are small branch offices that must access the
  core through Site A.
• Therefore, Dist-1 A is acting as a WAN hub for
  the organization. As the network scales, dozens
  of remote sites may access the core by connection
  to distribution routers at the WAN hubs, Site A,
  Site B, and Site C.  

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5 Characteristics of Scalable Networks

• Reliable and available A reliable network
  should be dependable and available 24 hours a
  day, seven days a week. In addition, failures
  need to be isolated, and recovery must be
  invisible to the end user.
• Responsive A responsive network should provide
  Quality of Service (QoS) for various applications
  and protocols without affecting a response at the
  desktop.
• Adaptable An adaptable network is capable of
  accommodating different protocols, applications,
  and hardware technologies.

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5 Characteristics of Scalable Networks

• Efficient Large internetworks must optimize the
  use of resources, especially bandwidth. Reducing
  the amount of overhead traffic, such as
  unnecessary broadcasts, service location, and
  routing updates, resulting in an increase in data
  throughput without increasing the cost of
  hardware or the need for additional WAN services.
  
• Accessible but secure An accessible network
  allows for connections using dedicated, dialup,
  and switched services while maintaining network
  integrity.

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Making The Network Reliable and Available

• Scalable Routing Protocols Routers in the core
  of a network should converge rapidly and maintain
  reachability to all networks and subnetworks
  within an Autonomous System (AS). A scalable
  protocol such as Open Shortest Path First (OSPF)
  or Enhanced Interior Gateway Routing Protocol
  (EIGRP) should be implemented in the core layer.
• A network that consists of multiple links and
  redundant routers will contain several paths to a
  given destination.

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Making The Network Reliable and Available

• Load Balancing Redundant links do not
  necessarily remain idle until a link fails.
  Routers can distribute the traffic load across
  multiple links to the same destination. This
  process is called load balancing. Load balancing
  can be implemented using alternate paths with the
  same cost or metric, (equal-cost load
  balancing.), or implemented over alternate paths
  with different metrics, (unequal-cost load
  balancing). When routing IP, the Cisco IOS offers
  two methods of load balancing, per packet and per
  destination load balancing. If process switching
  is enabled, the router will alternate paths on a
  per packet basis. If fast switching is enabled,
  only one of the alternate routes will be cached
  for the destination address and all packets in
  the packet stream bound for a specific host will
  take the same path.
• Protocol Tunnels The administrator can configure
  a point-to-point link through the core between
  the two routers using IP. When this link is
  configured, IPX packets can be encapsulated
  inside IP packets. IPX can then traverse the core
  over IP links and the core can be spared the
  additional burden of routing IPX. Using tunnels,
  the administrator increases the availability of
  network services.

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Making The Network Reliable and Available

• Dial Backup Sometimes two redundant WAN links
  are not enough or a single link needs to be fault
  tolerant, however a full-time redundant link is
  too expensive. In these cases a backup link can
  be configured over a dialup technology, such as
  ISDN, or even an ordinary analog phone line.
  These relatively low-bandwidth links remain idle
  until the primary link fails.
• Dial backup can be a cost-effective insurance
  policy, but it is not a substitute for redundant
  links that can effectively double throughput by
  using equal-cost load balancing.

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Making the network responsive

• The IOS addresses priority and responsiveness
  issues through queuing. The question of priority
  is most important on routers that maintain a slow
  WAN connection and therefore experience frequent
  congestion. Queuing refers to the process that
  the router uses to schedule packets for
  transmission during periods of congestion. By
  using the queuing feature, a congested router may
  be configured to reorder packets so that
  mission-critical and delay sensitive traffic is
  processed first. These higher priority packets
  are sent first even if other low priority packets
  arrive ahead of them.

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Making The Network Efficient

• An efficient network should not waste bandwidth,
  especially over costly WAN links. To be
  efficient, routers should prevent unnecessary
  traffic from traversing the WAN and should
  minimize the size and frequency of routing
  updates. The IOS includes several features
  designed to optimize a WAN connection
• Access lists
• Snapshot routing
• Compression over WANs
• Dial-on-demand routing (DDR)
• Route summarization
• Incremental updates

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Making The Network Adaptable

• EIGRP is an exceptionally adaptable protocol
  because it supports routing information for three
  routed protocols IP, IPX, and AppleTalk.
• The IOS also supports route redistribution.
• Mixing Routable and none routable protocols

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Making the Network Accessible But Secured

• Dialup and dedicated access Cisco routers can
  be directly connected to basic telephone service
  or digital services such as T1/E1. Dialup links
  can be used for backup or remote sites that need
  occasional WAN access, while dedicated leased
  lines provide a high-speed, high capacity WAN
  core between key sites.
• Packet switched Cisco routers support Frame
  Relay, X.25, Switched Multi-megabit Data Service
  (SMDS), and ATM. With this variety of support,
  the WAN service, or combination of WAN services,
  to deploy can be determined based on cost,
  location, and need.

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International Travel Agency
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International Travel Agency Topology
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International Travel Agency Locations
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Web-Based Curriculum

• Follow the link
• http//curweb1.netacaddev.net/beta
• User Name plethora
• Password aCCeSSory

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Labs ?

• Lab1.4.3  Access Control Lists basic and
  extended Ping
• Lab 1.4.2  Capturing HyperTerminal and Telnet
  Sessions
• Lab 1.4.4  Implementing Quality of Service with
  Priority Queuing
• Lab 1.5.2  Unequal-Coast Load Balancing with
  IGRP