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CCNA3 Final Exam Review

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Title: CCNA3 Final Exam Review


1
CCNA3 Final Exam Review
  • Version 3.1 2006/2007

2
1.1.3 When to use VLSM
3
1.1.4 Calculating subnets with VLSM
4
1.1.5 Route aggregation with VLSM
5
1.2.2 RIP v2 features
  • Both versions of RIP share the following
    features
  • It is a distance vector protocol that uses a
    hop count metric.
  • It uses holddown timers to prevent routing
    loops default is 180 seconds.
  • It uses split horizon to prevent routing
    loops.
  • It uses 16 hops as a metric for infinite
    distance.

6
1.2.4 Configuring RIP v2
  • To configure RIP v2 on a Cisco router, the
    following tasks must be completed
  • Select a routing protocol, such as RIP v2.
  • Assign the IP network numbers without
    specifying the subnet values.
  • Assign the network or subnet addresses and
    the appropriate subnet mask to the interfaces.

7
1.2.4 Configuring RIP v2
8
1.2.7 Default routes
  • By default, routers learn paths to destinations
    three different ways
  • Static routes The system administrator manually
    defines the static routes as the next hop to a
    destination. Static routes are useful for
    security and traffic reduction, as no other route
    is known.
  • Default routes The system administrator also
    manually defines default routes as the path to
    take when there is no known route to the
    destination. Default routes keep routing tables
    shorter. When an entry for a destination network
    does not exist in a routing table, the packet is
    sent to the default network.
  • Dynamic routes Dynamic routing means that the
    router learns of paths to destinations by
    receiving periodic updates from other routers.

9
1.2.7 Default routes
10
1.2.7 Default routes
11
1.2.7 Default routes
  • HongKong1(config)ip route 0.0.0.0 0.0.0.0 s0/0
  • The zeros in the IP address and mask portions of
    the command represent any destination network
    with any mask. Default routes are referred to as
    quad zero routes. In the diagram, the only way
    Hong Kong 1 can go to the Internet is through
    interface s0/0.

12
2.1.1 Overview of link-state routing
13
2.3.1 Configuring OSPF routing process
14
2.3.2 Configuring OSPF loopback address and
router priority
  • If the network type of an interface is broadcast,
    the default OSPF priority is 1. When OSPF
    priorities are the same, the OSPF election for DR
    is decided on the router ID. The highest router
    ID is selected. When the OSPF process starts, the
    Cisco IOS uses the highest local active IP
    address as its OSPF router ID.
  • The election result can be determined by ensuring
    that the ballots, the hello packets, contain a
    priority for that router interface. The interface
    reporting the highest priority for a router will
    ensure that it becomes the DR.
  • The priorities can be set to any value from 0 to
    255. A value of 0 prevents that router from being
    elected. A router with the highest OSPF priority
    will be selected as the DR.

15
2.3.3 Modifying OSPF cost metric
  • OSPF uses cost as the metric for determining the
    best route. This is the highlighted portion of
    the show ip route output above.

16
2.3.4 Configuring OSPF authentication
  • A network administrator would choose to enable
    authentication for OSPF exchanges for two
    reasons
  • To prevent routing information from being
    falsified
  • To ensure that routing information comes from a
    valid source

17
3.1.3 EIGRP design features
  • EIGRP sends partial, bounded updates and makes
    efficient use of bandwidth.
  • This is similar to OSPF operation, except that
    EIGRP routers send these partial updates only to
    the routers that need the information, not to all
    routers in an area.
  • Instead of timed routing updates, EIGRP routers
    use small hello packets to keep in touch with
    each other. Though exchanged regularly, hello
    packets do not use up a significant amount of
    bandwidth.
  • EIGRP supports IP, IPX, and AppleTalk through PDMs

18
3.2.1 Configuring EIGRP
  • Perform the following steps to configure EIGRP
    for IP
  • 1. Use the following to enable EIGRP and
    define the autonomous system
  • router(config)router eigrp
    autonomous-system-number
  • 2. Indicate which networks belong to the EIGRP
    autonomous system on the local router by using
    the following command
  • router(config-router)networknet
    work-number
  • The network-number is the network number
    that determines which interfaces of the router
    are participating in EIGRP and which networks are
    advertised by the router.

19
3.2.2 Configuring EIGRP Summarization
  • Automatic summarization may not be the preferred
    option in certain instances. For example, if
    there are discontiguous subnetworks
    auto-summarization must be disabled for routing
    to work properly

20
3.2.4 Building neighbor tables
  • EIGRP routers establish adjacencies with neighbor
    routers by using small hello packets.

21
4.1.9 Full-duplex transmitting
  • Full-duplex Ethernet allows the transmission of a
    packet and the reception of a different packet at
    the same time. This connection is considered
    point-to-point and is collision free. Because
    both nodes can transmit and receive at the same
    time, there are no negotiations for bandwidth.
  • Full-duplex Ethernet offers 100 percent of the
    bandwidth in both directions. This produces a
    potential 20 Mbps throughput, which results from
    10 Mbps TX and 10 Mbps RX

22
4.2.4 LAN segmentation with switches
  • Switches decrease bandwidth shortages and network
    bottlenecks, such as those between several
    workstations and a remote file server. Figure
    shows a Cisco switch. Switches segment LANs into
    microsegments which decreases the size of
    collision domains. However, all hosts connected
    to a switch are still in the same broadcast
    domain.

23
4.2.10 Two switching methods
  • The following two switching modes are available
    to forward frames
  • Store-and-forward - The entire frame is
    received before any forwarding takes place. The
    destination and source addresses are read and
    filters are applied before the frame is
    forwarded. Latency occurs while the frame is
    being received. Latency is greater with larger
    frames because the entire frame must be received
    before the switching process begins. The switch
    is able to check the entire frame for errors,
    which allows more error detection.
  • Cut-through - The frame is forwarded
    through the switch before the entire frame is
    received. At a minimum the frame destination
    address must be read before the frame can be
    forwarded. This mode decreases the latency of the
    transmission, but also reduces error detection.

24
4.2.10 Two switching methods
  • The following are two forms of cut-through
    switching
  • Fast-forward - Fast-forward switching
    offers the lowest level of latency. Fast-forward
    switching immediately forwards a packet after
    reading the destination address. Because
    fast-forward switching starts forwarding before
    the entire packet is received, there may be times
    when packets are relayed with errors. Although
    this occurs infrequently and the destination
    network adapter will discard the faulty packet
    upon receipt. In fast-forward mode, latency is
    measured from the first bit received to the first
    bit transmitted.
  • Fragment-free - Fragment-free switching
    filters out collision fragments before forwarding
    begins. Collision fragments are the majority of
    packet errors. In a properly functioning network,
    collision fragments must be smaller than 64
    bytes. Anything greater than 64 bytes is a valid
    packet and is usually received without error.
    Fragment-free switching waits until the packet is
    determined not to be a collision fragment before
    forwarding. In fragment-free mode, latency is
    also measured from the first bit received to the
    first bit transmitted.

25
5.2.1 Switched LANs, access layer overview
  • The three layers of the hierarchical design model
    are
  • The access layer provides users in workgroups
    access to the network.
  • The distribution layer provides policy-based
    connectivity.
  • The core layer provides optimal transport between
    sites. The core layer is often referred to as the
    backbone.

26
5.2.3 Distribution layer overview
  • The following are some of the distribution layer
    functions in a switched network
  • Aggregation of the wiring closet connections
  • Broadcast/multicast domain definition
  • VLAN routing
  • Any media transitions that need to occur
  • Security

27
5.2.4 Distribution layer switches
  • The following Cisco switches are suitable for the
    distribution layer
  • Catalyst 2926G
  • Catalyst 5000 family
  • Catalyst 6000 family

28
6.1.3 Verifying port LEDs during switch POST
29
6.2.2 Configuring the Catalyst switch
  • Some network devices can provide a web-based
    interface for configuration and management
    purposes.
  • Once a switch is configured with an IP address
    and gateway, it can be accessed in this way.
  • A switch should be given a hostname, and
    passwords should be set on the console and vty
    lines..
  • Activate HTTP service.

30
6.2.2 Configuring the Catalyst switch
  • A switch should be assigned an IP address so that
    it can be accessed remotely using Telnet or other
    TCP/IP applications.
  • Paris telnet 198.19.27.251( IP address of switch
    in Denver)

31
6.2.2 Configuring the Catalyst switch
32
6.2.4 Configuring static MAC addresses
  • The following command can be used to remove a
    static MAC address for a switch
  • Switch(config)no mac-address-table static
    ltmac-address of host gt interface FastEthernet
    ltEthernet number gt vlan ltvlan name gt

33
7.2.1 Redundant topology and spanning tree
  • Spanning-Tree Protocol (STP) is a Layer 2 link
    management protocol that provides path redundancy
    while preventing undesirable loops in switched or
    bridged networks. STP operation is transparent to
    end stations. STP runs on Layer 2 switches,
    bridges, and routers configured to operate as
    bridges.

34
7.2.2 Spanning-tree protocol
  • The switches and bridges on a network use an
    election process over STP to configure a single
    logical path.
  • Step Action
  • 1 Selection of root bridge
  • 2 Configurations are made by the other switches
    and bridges, using the root bridge as a reference
    point.
  • 3 Each bridge or switch now determines which of
    its own ports offers the best path to the root
    bridge.
  • 4 The logical loop is removed by one of the
    switches or bridges by blocking the port that
    creates the logical loop. Blocking is done by
    calculating costs for each port in relation to
    the root bridge. Then the port with the highest
    cost is disabled.

35
7.2.4 Selecting the root bridge
  • Network administrators can set the switch
    priority to a smaller value than the default,
    which makes the BID smaller. This should only be
    implemented when the traffic flow on the network
    is well understood.

36
7.2.4 Selecting the root bridge
  • All switches receive the BPDUs and determine that
    the switch with the lowest root BID value will be
    the root bridge.
  • The BID consists of a bridge priority that
    defaults to 32768 and the switch MAC address.

37
7.2.5 Stages of spanning-tree port states
38
8.1.3 VLAN operation
  • The default VLAN for every port in the switch is
    the management VLAN. The management VLAN is
    always VLAN 1 and may not be deleted. At least
    one port must be assigned to VLAN 1 in order to
    manage the switch. All other ports on the switch
    may be reassigned to alternate VLANs.

39
8.2.3 Configuring static VLANs
  • To assign the VLAN to one or more interfaces
  • Switch_A(config)interface fastethernet 0/2
  • Switch_A(config-if)switchport mode access
  • Switch_A(config-if)switchport access vlan 2

40
8.2.4 Verifying VLAN configuration
  • The following facts apply to VLANs
  • A created VLAN remains unused until it is mapped
    to switch ports.
  • All Ethernet ports are assigned to VLAN 1 by
    default.

41
9.1.5 Trunking implementation
  • Trunking protocols were developed to effectively
    manage the transfer of frames from different
    VLANs on a single physical line.
  • The trunking protocols establish agreement for
    the distribution of frames to the associated
    ports at both ends of the trunk.
  • This allows hosts on the same VLAN to communicate
    with one another across different switches

42
9.2.1 History of VTP
  • To maintain connectivity within VLANs, each VLAN
    must be manually configured on each switch. As
    the organization grows and additional switches
    are added to the network, each new switch must be
    manually configured with VLAN information. A
    single incorrect VLAN assignment could cause two
    potential problems
  • Cross-connected VLANs due to VLAN configuration
    inconsistencies
  • VLAN misconfiguration across mixed media
    environments such as Ethernet and Fiber
    Distributed Data Interface (FDDI)
  • With VTP, VLAN configuration is consistently
    maintained across a common administrative domain.
    Additionally, VTP reduces management and
    monitoring complexities of networks with VLANs.

43
9.3.6 Configuring inter-VLAN routing
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