CCNA3 Final Exam Review

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CCNA3 Final Exam Review

• Version 3.1 2006/2007

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1.1.3 When to use VLSM
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1.1.4 Calculating subnets with VLSM
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1.1.5 Route aggregation with VLSM
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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.

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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.

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1.2.4 Configuring RIP v2
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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.

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1.2.7 Default routes
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1.2.7 Default routes
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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.

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2.1.1 Overview of link-state routing
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2.3.1 Configuring OSPF routing process
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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.

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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.

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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

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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

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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.

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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

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3.2.4 Building neighbor tables

• EIGRP routers establish adjacencies with neighbor
  routers by using small hello packets.

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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

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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.

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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.

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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.

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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.

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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

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5.2.4 Distribution layer switches

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

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6.1.3 Verifying port LEDs during switch POST
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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.

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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)

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6.2.2 Configuring the Catalyst switch
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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

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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.

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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.

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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.

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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.

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7.2.5 Stages of spanning-tree port states
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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.

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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

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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.

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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

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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.

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9.3.6 Configuring inter-VLAN routing