Final Exam Review

1
Final Exam Review

• CCNA3 version 3.1

2
1.1.3 When to use VLSM
3
1.1.4 Calculating subnets with VLSM

• With VLSM it is possible to subnet 172.16.32.0/20
  to create more network addresses with fewer hosts
  per network. When 172.16.32.0/20 is subnetted to
  172.16.32.0/26, there is a gain of 26, or 64
  subnets. Each subnet can support 26 2, or 62
  hosts.
• Use the following steps to apply VLSM to
  172.16.32.0/20
• Write 172.16.32.0 in binary form.
• Draw a vertical line between the 20th and 21st
  bits, as shown in Figure . The original subnet
  boundary was /20.
• Draw a vertical line between the 26th and 27th
  bits, as shown in Figure . The original /20
  subnet boundary is extended six bits to the
  right, which becomes /26.
• Calculate the 64 subnet addresses with the bits
  between the two vertical lines, from lowest to
  highest in value. The figure shows the first five
  subnets available.

4
1.1.5 Route aggregation with VLSM
5
1.2.2 RIP v2 features

• RIP v2 provides prefix routing, which allows it
  to send out subnet mask information with the
  route update. Therefore, RIP v2 supports the use
  of classless routing in which different subnets
  within the same network can use different subnet
  masks, as in VLSM.
• RIP v2 provides for authentication in its
  updates. A set of keys can be used on an
  interface as an authentication check. RIP v2
  allows for a choice of the type of authentication
  to be used in RIP v2 packets. The choice can be
  either clear text or Message-Digest 5 (MD5)
  encryption. Clear text is the default. MD5 can be
  used to authenticate the source of a routing
  update. MD5 is typically used to encrypt enable
  secret passwords and it has no known reversal.
• RIP v2 multicasts routing updates using the Class
  D address 224.0.0.9, which provides for better
  efficiency.

6
1.2.4 Configuring RIP v2

• To enable a dynamic routing protocol, 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
1.2.7 Default routes
8
2.1.1 Overview of link-state routing
9
2.3.1 Configuring OSPF routing process

• To enable OSPF routing, use the global
  configuration command syntax
• Router(config)router ospfprocess-id The process
  ID is a number that is used to identify an OSPF
  routing process on the router. The number can be
  any value between 1 and 65,535.
• IP networks are advertised as follows in OSPF
• Router(config-router)network address
  wildcard-mask area area-id Each network must be
  identified with the area to which it belongs. The
  network address can be a whole network, a subnet,
  or the address of the interface. The wildcard
  mask represents the set of host addresses that
  the segment supports.

10
2.3.2 Configuring OSPF loopback address and
router priority

• A router with the highest OSPF priority will be
  selected as the DR.
• A value of 0 prevents that router from being
  elected.
• The priorities can be set to any value from 0 to
  255.

11
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.
• On a router that has more than one interface,
  OSPF takes the highest IP address as its router
  ID.

12
2.3.2 Configuring OSPF loopback address and
router priority

• Modify the OSPF priority by entering global
  interface configuration ip ospf priority command
  on an interface that is participating in OSPF.
  The command show ip ospf interface will display
  the interface priority value as well as other key
  information.
• Router(config-if)ip ospf prioritynumber
  Routershow ip ospf interfacetype number

13
2.3.3 Modifying OSPF cost metric

• In the output listed below the number 782 is the
  metric, and cost for this route

14
2.3.4 Configuring OSPF authentication

• By default, a router trusts that routing
  information is coming from a router that should
  be sending the information. A router also trusts
  that the information has not been tampered with
  along the route.
• To guarantee this trust, routers in a specific
  area can be configured to authenticate each
  other.
• Authentication also confirms that the source and
  contents of the packet have not been tampered
  with.

15
3.1.3 EIGRP design features

• EIGRP supports IP, IPX, and AppleTalk through
  PDMs.
• EIGRP sends partial, bounded updates and makes
  efficient use of bandwidth.
• 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.

16
3.2.1 Configuring EIGRP

• Perform the following steps to configure EIGRP
  for IP
• Use the following to enable EIGRP and define the
  autonomous system router(config)router eigrp
  autonomous-system-number
• Indicate which networks belong to the EIGRP
  autonomous system on the local router by using
  the following command router(config-router)netwo
  rknetwork-number
• The network command configures only connected
  networks. For example, network 3.1.0.0, which is
  on the far left of the main Figure, is not
  directly connected to Router A. Consequently,
  that network is not part of the configuration of
  Router A.
• Cisco also recommends adding the following
  command to all EIGRP configurations
  router(config-router)eigrp log-neighbor-changes

17
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.

18
3.2.4 Building neighbor tables

• EIGRP routers establish adjacencies with neighbor
  routers by using small hello packets. Hellos are
  sent by default every five seconds.

19
4.1.9 Full-duplex transmitting

• Full-duplex Ethernet offers 100 percent of the
  bandwidth in both directions.
• 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.

20
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.
• 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.
• In a completely switched Ethernet LAN, the source
  and destination nodes function as if they are the
  only nodes on the network. When these two nodes
  establish a link, or virtual circuit, they have
  access to the maximum available bandwidth.

21
4.2.5 Basic operations of a switch

• This reduction results in more efficient use of
  bandwidth and increased throughput. LAN switches
  often replace shared hubs and are designed to
  work with cable infrastructures already in place.

22
4.2.10 Two switching methods

• 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.

23
5.2.1 Switched LANs, access layer overview
24
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

25
5.2.4 Distribution layer switches

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

26
6.1.3 Verifying port LEDs during switch POST
27
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.
• A switch should be assigned a default gateway so
  that when working from the command line
  interface, other networks can be accessed.

28
6.2.2 Configuring the Catalyst switch

• Establish Connectivity.
• Once a switch is configured with an IP address
  and gateway, it can be accessed in this way.
• A web browser can access this service using the
  IP address and port 80, the default port for
  http. The HTTP service can be turned on or off,
  and the port address for the service can be
  chosen.

29
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.

30
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

31
7.2.1 Redundant topology and spanning tree

• The Spanning-Tree Protocol is a Layer 2 link
  management protocol used to maintain a loop-free
  network.
• The algorithm used to create this loop free
  logical topology is the spanning-tree algorithm.

32
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.
• StepAction
• 1Selection of root bridge
• 2Configurations are made by the other switches
  and bridges, using the root bridge as a reference
  point.
• 3Each bridge or switch now determines which of
  its own ports offers the best path to the root
  bridge.
• 4The 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.

33
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.
• The BID consists of a bridge priority that
  defaults to 32768 and the switch MAC address.
• All switches receive the BPDUs and determine that
  the switch with the lowest root BID value will be
  the root bridge

34
7.2.5 Stages of spanning-tree port states

• Ports transitions from the learning state to the
  forwarding state. In this state user data is
  forwarded and MAC addresses continue to be
  learned. BPDUs are still processed.

35
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.

36
8.2.3 Configuring static VLANs

• assign the VLAN to one or more interfaces
• Switch(config)interface fastethernet 0/9
  Switch(config-if)switchport access vlan
  vlan_number

37
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.

38
9.1.5 Trunking implementation

• Creating trunk links between two switches allows
  communication between paired VLANs.

39
9.2.1 History of VTP
40
9.3.6 Configuring inter-VLAN routing

• To define subinterfaces on a physical interface,
  perform the following tasks
• Identify the interface.
• Define the VLAN encapsulation.
• Assign an IP address to the interface.