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CCNP 1: Building Scalable Cisco Internetworks

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Title: CCNP 1: Building Scalable Cisco Internetworks


1
CCNP 1 Building Scalable Cisco Internetworks
  • Overview Of Scalable Networks

2
The Hierarchical Network Design Model
Make sure that you visit the following link
Internetworking Design Basics
3
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.

4
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.

5
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.

6
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.

7
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.

8
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

9
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.

10
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

11
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.

12
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.  

13
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.

14
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.

15
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.

16
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.

17
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.

18
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.

19
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

20
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

21
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.

22
International Travel Agency
23
International Travel Agency Topology
24
International Travel Agency Locations
25
Web-Based Curriculum
  • Follow the link
  • http//curweb1.netacaddev.net/beta
  • User Name plethora
  • Password aCCeSSory

26
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
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