1. To relieve network congestion more bandwidth is needed or the available of it must be used more efficiently.
2. A network can be divided into smaller units called segments. Each segment uses the Carrier Sense Multiple Access/Collision Detection protocol and maintains traffic between users on the segment. By using segments in a network less users/devices are sharing the same 10Mbps when communicating to one another within the segment. Each segment is considered its own collision domain.
3. In a segmented Ethernet LAN, data passed between segments is transmitted on the backbone of the network using a bridge, switch or router.
4. A LAN which uses a switched Ethernet topology creates a network that behaves like it only has two nodes: the sending node and the receiving node.
5. The purpose for using LAN switching is to ease bandwidth shortages and network bottlenecks, such as between several PCs and a remote file server. A LAN switch is a very high-speed multiport bridge with one port for each node or segment of the LAN. A switch segments a LAN into microsegments creating collision free domains from one larger collision domain.
6. Switches achieve this high speed transfer by reading the destination layer 2 MAC address of the packet much like a bridge does. The packet is sent to the port of the receiving station prior to the entire packet entering the switch. This leads to low latency levels and a high rate of speed for packet forwarding.
7. Ethernet switching increases the bandwidth available on a network. It does this by creating dedicated network segments (point-to-point connections) and connecting those segments in a virtual network within the switch. This virtual network circuit exists only when two nodes need to communicate. This is why it is called a virtual circuit—it exists only when needed and is established within the switch.
8. Even though the LAN switch creates dedicated, collision-free domains, all hosts connected to the switch are still in the same broadcast domain.
9. An Ethernet switch can learn the address of each device on the network by:
· reading the source address of each packet transmitted
· noting the port where the frame was heard
10. The switch then adds this information to its forwarding database. Addresses are learned dynamically. This means that as new addresses are read they are learned and stored in content addressable memory (CAM) and stored for future use and each time an address is stored it is time stamped.
11. A(n) symmetric switch provides switched connections between ports with the same bandwidth, such as all 10 Mbps or all 100 Mbps ports.
12. A(n) asymmetric LAN switch provides switched connections between ports of unlike bandwidth, such as a combination of 10 Mbps and 100 Mbps ports.
13. Memory buffering in an asymmetric switch is required to allow traffic from the 100 Mbps port to be sent to a 10 Mbps port without causing too much congestion at the 10 Mbps port.
14. To accomplish faster frame forwarding, the switch takes less time to check for errors. The trade off can lead to a higher number of re-transmissions.
15. There are two ways to forward frames through a switch:
· Store and Forward - the entire frame is received before any forwarding takes place. The destination and/or the source addresses are read and filters are applied before the frame is forwarded. Latency occurs while the frame is being received; the latency is greater with larger frames because the entire frame takes longer to read. Error detection is high because of the time available to the switch to check for errors while waiting for the entire frame to be received.
· Cut-Through (Fast Forward/Fragment-Free) - the switch reads the destination MAC address and begins forwarding the frame before it is completely received. This mode decreases the latency of the transmission and has poor error detection.
16. VLANs logically segment the physical LAN infrastructure into different subnets (broadcast domains for Ethernet) so that broadcast frames are switched only between ports within the same VLAN.
17. Frame filtering is a technique that examines particular information about each frame. The concept of frame filtering is very similar to that commonly used by routers. A filtering table is developed for each switch, which provides a high level of administrative control because it can examine many attributes of each frame.
18. Frame identification (frame tagging) uniquely assigns a user-defined ID to each frame. This technique was chosen by the IEEE standards group because of its scalability.
19. VLANs are an effective mechanism for extending firewalls from the routers to the switch fabric and protecting the network against potentially dangerous broadcast problems. These firewalls are accomplished by assigning switch ports or users to specific VLAN groups both within single switches and across multiple connected switches.
20. VLAN membership by port is a preferred method of setting up VLANs because they maximizes forwarding performance.
21. Dynamic VLAN functions are based on MAC addresses, logical addressing, or protocol type of the data packets.
22. The first step in designing a Local Area Network (LAN) is to establish and document the goals of the design. These goals will be particular to each organization or situation. However, general requirements tend to show up in any network design:
· Functionality -- The network must work. That is, it must allow users to meet their job requirements. The network must provide user-to-user and user-to-application connectivity with reasonable speed and reliability.
· Scalability -- The network must be able to grow. That is to say, the initial design should grow without any major changes to the overall design.
· Adaptability -- The network must be designed with an eye toward future technologies, and should not include elements that would limit implementation of new technologies as they become available.
· Manageability -- The network should be designed to facilitate network monitoring and management, in order to ensure ongoing stability of operation
23. Media contention refers to excessive collisions on Ethernet caused by too many devices, all with a high demand for the network segment.
24. The number of broadcasts become excessive when there are too many client packets looking for services, too many server packets announcing services, too many routing table updates, and too many other broadcasts dependent on protocols such as ARP.
25. After the requirements for the overall network have been gathered, an overall topology, or model, of the LAN can be developed. The major pieces of this topology design can be broken into three unique categories of the OSI model.
· Layer 1 - Physical Layer
· Build this layer of the OSI model with speed and expansion capabilities.
·
Layer 2 -
Data Link Layer
· Create a concentration point within the MDFs or IDFs where end hosts can be grouped at Layer 1 to form a physical LAN segment.
· Install LAN switching devices that use microsegmentation in order to reduce the collision domain size.
· Create a point (at Layer 2) of the topology where users can be grouped into virtual workgroups (VLANs) and unique broadcast domains.
·
Layer 3 -
Network Layer
· Build a path between LAN segments that will filter the flow of data packets.
· Isolate ARP broadcasts.
· Isolation of collisions between segments.
· Filtering of Layer 4 services between segments.
26. Cisco suggests that you have certain types of cable for horizontal runs and vertical runs. Complete the table below according to the recommendations.
|
Type |
Type of Cable |
Speed |
Maximum Length |
|
Horizontal Run |
UTP Cat 5 |
10 or 100 Mbps |
90 m. |
|
Vertical IDF to MDF |
Single mode fiber |
100 Mbps |
3000 m. |
|
Vertical VCC in IDF to MDF |
Single mode fiber |
100 Mbps |
3000 m. |
|
Servers |
UTP Cat 5 |
100 Mbps |
100 m. |
27. The success of dynamic routing depends on two basic router
functions:
·
Maintenance of a
routing table
·
Timely distribution
of knowledge—in the form of routing updates—to other routers
28. A routing protocol describes:
·
How updates are
sent
·
What knowledge
is contained in these updates
·
When to send this knowledge
·
How to locate
recipients of the updates
29. The smaller the metric number, the better the path.
30. Metric values can be calculated based on a single characteristic of a path. You can calculate more complex metrics by combining several characteristics. Several path characteristics are used in the calculations. The metrics most commonly used by routers follow:
· Bandwidth - Data capacity of a link. For instance, normally, a 10-Mbps Ethernet link is preferable to a 64-kbps leased line.
· Delay - Length of time required to move a packet from source to destination.
· Load - Amount of activity on a network resource such as a router or link.
· Reliability - Usually refers to the error rate of each network link.
· Hop count - Number of routers a packet must pass through.
· Ticks - Delay on a data link using IBM PC clock ticks (approximately 55 milliseconds).
· Cost - Arbitrary value, usually based on bandwidth, dollar expense, or other measurement, that is assigned by a network administrator.
31. Most routing protocols are based on one of two routing algorithms: distance-vector or link-state.
32. The knowledge base needs to reflect an accurate, consistent view of the new topology. Convergence occurs when all routers in an internet are operating with the same knowledge (i.e. all routers have the same information on all the paths in the network).
33. Exterior
routing protocols are used to communicate between autonomous systems. Interior
routing protocols are used within a single autonomous system.
34. Examples of Interior IP routing protocols include:
· RIP -A distance vector routing protocol.
· IGRP -Cisco's distance vector routing protocol.
· OSPF -A link-state routing protocol.
· EIGRP -A balanced hybrid routing protocol.
35. IGRP is a distance-vector routing protocol developed by Cisco. IGRP sends routing updates at 90-second intervals that advertise networks for a particular autonomous system.
36. IGRP may use a combination of variables to determine a composite metric.
37. Access lists allow an administrator to specify conditions that determine how a router will control traffic flow. Access lists are used to permit or deny traffic through a router interface. The two main types of access lists are:
· Standard access lists, which check the source address of packets that could be routed. The result permits or denies output for an entire protocol suite, based on the network/subnet/host address.
· Extended access lists which check for source and destination packet addresses. They also can check for specific protocols, port numbers, and other parameters. This allows administrators more flexibility to describe what checking the access list will do. Packets can be permitted or denied output based on where the packet originated and on its destination.
38. Access lists express the set of rules that give added control for packets that enter inbound interfaces or outbound interfaces of the router. Access lists do not act on packets that originate in the router itself.
39. There can be only one access list per protocol, per interface, per direction.
40. With Cisco IOS Release 11.2 and later you can also identify a standard or extended IP access list with an alphanumeric string (name) instead of the current numeric (1 to 199) representation.
41. IP access lists use wildcard masking.
· A wildcard mask bit 0 means "check the corresponding bit value."
· A wildcard mask bit 1 means "do not check (ignore) that corresponding bit value."
42. The administrator can use the abbreviation any to represent 0.0.0.0 255.255.255.255.
43. To represent 172.30.16.29 0.0.0.0, the administrator can use the word host in front of the address.
44. The rule with extended access lists is to put the extended access list as close as possible to the source of the traffic denied.
45. Standard access lists do not specify destination addresses. The administrator would have to put the standard access list as near the destination as possible.
46. Novell IPX has the following characteristics:
· it is a connectionless protocol that does not require acknowledgments for each packet (best effort delivery)
and
· it is a Layer 3 protocol that defines internetwork and internode addresses.
47. Novell IPX addressing uses a two-part address, the network number and the node number. The IPX network number can be up to eight hexadecimal digits in length. Usually, only the significant digits are listed. This number is assigned by the network administrator.
48. Each interface retains its own address. The use of the MAC address in the logical IPX address eliminates the need for ARP.
49. When you configure an IPX network, you may need to specify an encapsulation type on either the Novell servers and clients or on the Cisco router. Make sure the encapsulations on the clients, servers, and routers all match. If you do not specify an encapsulation type when you configure the router for IPX, the router will use the default encapsulation type on its interfaces.
50. The default encapsulation types on Cisco router interfaces and their keywords are:
· Ethernet: novell-ether
· Token Ring: sap
· FDDI: snap
51. Novell RIP is a distance vector routing protocol. Novell RIP uses two metrics to make routing decisions: ticks (a time measure) and hop count (a count of each router traversed).
52. If two or more paths have the same tick and hop count, the router will load share based on the ipx maximum-paths command.
53. All servers and routers keep a complete list of the services available throughout the network in server information tables.
54. By default, service advertisements occur at 60-second intervals.
55. Routers do not forward SAP broadcasts. Instead, each one builds its own SAP table and forwards the SAP table to others.
56. Circle
the correct term to make the statement true.
If a NetWare server is located on the segment, it will respond to the client
request. The Cisco router (will/will not) respond to the GNS request. If
there are no NetWare servers on the local network, the Cisco router will
respond with a server address from its own SAP table.