CCNA Practice.txt

• A. Production# show interfaces, E. Production# show ip interface, F. Production# show protocols

^{"show interfaces" is used to see the IP addresses and layer 2 information configured on the interfaces. "show controllers" is used to see the layer 1 stats. It tells about the V.35 cables: whether they are physically attached or not. "show interfaces" is used to see the IP add's configured on the interfaces.}

• C. the lowest IP address among its active interfaces

^{Ordinarily the loopback interface would be selected as the router ID. In the event that no loopback interface is configured, the router ID will be the first active interface that comes up on the router. If that particular interface has more than one IP address, the highest address will be selected as the router ID.}

• B. a method of VLAN trunking

• ^{A broadcast domain must sometimes exist on more than one switch in the network. To accomplish this, one must send frames to another switch and indicate which VLAN a particular frame belongs to. On Cisco switches, a trunk line is created to accomplish this VLAN identification. ISL and IEEE 802.1Q are different methods of putting a VLAN identifier in a Layer 2 frame. the IEEE 802.1Q protocol interconnects VLANs between multiple switches, routers, and servers.}
• With IEEE 802.1Q, a network admin can define a VLAN topology to span multiple physical devices. Cisco switches support IEEE 802.1Q for Fast Ethernet and Gigabit Ethernet interfaces.
• An IEEE 802.1Q trunk link provides VLAN identification by adding a 4-byte tag to an Ethernet Frame as it leaves a trunk port.

• C. 4094

^{Given IP address 172.16.112.1/20, the subnet mask would be 255.255.240.0}

• C. Configure a separate subinterface for each PVC with a unique DLCI and subnet assigned to the sub-interface

• ^{Point-to-Point Subinterfaces:}
• The concept of subinterfaces was originally created in order to better handle issues caused by split-horizon over Non-Broadcast Multiple Access (NBMA) networks (e.g. frame relay, X.25) and distance-vector based routing protocols (e.g. IPX RIP/SAP, Appletalk). Split-horizon dictates that a routing update received on an interface cannot be retransmitted out onto the same interface. This rule holds even if the routing update was received on one frame relay PVC and destined to retransmit out onto another frame relay PVC. Referring to figure 2, this would mean that sites B and C can exchange routing information with site A, but would not be able to exchange routing information with each other. Split-horizon does not allow site A to send routing updates received from site B on to site C and vice versa.

Note: for TCP/IP, Cisco routers can disable split-horizon limitations on all frame relay interfaces and multipoint subinterfaces and do this by default. However, split-horizon cannot be disabled for other protocols like IPX and AppleTalk. These other protocols must use subinterfaces if dynamic routing is desired.

By dividing the partially-meshed frame relay network into a number of virtual, point-to-point subinterfaces, the split-horizon problem can be overcome. Each new point-to-point subnetwork is assigned its own network number. To the routed protocol, each subnetwork now appears to be located on separate interfaces. Routing updates received from site B on one logical point-to-point subinterface can be forwarded to site C on a separate logical interface without violating split-horizon.

• B. switch to host
• D. switch to switch
• E. host to host
• ^{Full-duplex Ethernet uses two pairs of wires, instead of one pair like half-duplex. And full duplex uses a point-to-point connection between the transmitting device and the receiving device. This means that w/full duplex you get a faster data transfer. And because data is sent/received on different sets of wire, no collisions occur.}

• D. Switch(config)# ip default-gateway 192.168.12.1
• ^{IP default-gateway address is a global command that sets the default gateway so the mgmt interface can be reached from a remote network. [CCNA ICND p.14]}

• A. resolves NBMA split horizon issues , C. maps one IP subnet per DLCI
• ^{Frame relay networks fall under the umbrella of Non-Broadcast Multi-Access (NBMA) networks. As the name implies, these networks allow multiple devices to access the network, but do not allow broadcasts btwn them. Altho this is default behavior, you can config the router to treat the network however you like. Because NBMA networks allow traffic btwn only the sites for which you purchase PVCs, this leads to some very odd configs. The hub and spoke topology can be very confusing to manage until you understand the problems with these network types. One of the major problems is that of running distance vector routing protocols over a frame relay network. These protocols (RIP, IGRP, EIGRP) have split-horizon.}

• E. data link
• ^{CDP is a device discovery protocol that runs over Layer 2 (data link) on all Cisco gear and allows network mgmt apps to discover Cisco devices that are neighbors of already known devices. With CDP, net. mgmt app's can learn the device type and SNMP agent address of neighbor devices running lower layer, transparent protocols.}

• D. 255.255.255.252

^{only 2 IPs are required. duh!}

• C. to logically group hosts according to function, E. to isolate broadcast traffic, F. to increase network security
• ^{Main functions of a VLAN}: can group several broadcast domains into multiple logical subnets. You can accomplish network additions, moves, and changes by configuring a port into the appropriate VLAN. You can place a group of users who need high security into a VLAN so that no users outside of the VLAN can communicate with them. As a logical grouping of users by function, VLANs can be considered independent from their physical/geographical locations. VLANs can enhance security, and increase number of broadcast domains while decreasing their size.

• D. a scheme to conserve public addresses, E. addresses that cannot be routed through the public internet
• Private IP address space has been allocated via RFC 1918. This means the addresses are available for use by anyone and therefore the same private IP addresses can be reused.

• A. combining routes to multiple networks into one supernet

^{Route aggregating is combining routes to multiple networks into one. AKA route summarization or supernetting. Normally used to reduce the number of route entries in the routing table by advertising numerous routes into one larger route.}

• E. to prevent unauthorized hosts from accessing the LAN

• B. IP addresses can be conserved if VLSM is not being used for subnetting
• ^{Frame relay supports two types of interfaces}: point-to-point and multipoint. The one you choose determines whether you need to use the config commands that ensure IP address to datalinkconnection identifier (DLCI) mappings. After configuring the PVC itself, you must tell the router which PVC to use in order to reach a specific destination. Use the frame-relay interface-dlci command to assign a DLCI to a specified Frame Relay subinterface.

• E. used to validate the sources of VTP advertisements sent btwn switches
• ^{VTP passwords help to authenticate the VTP clients as members of the same VTP domain, while authenticated VTP servers start advertisements to VTP clients. The VTP password and domain should be the same for both the VTP server and client.}

• C. debug PPP authentication
• ^{Whenever you're asked to display a process in real time, you must use a debug command as show commands do not display anything in real time. This command will display the authentication process of a PPP line, including the CHAP process}.

• D. It uses the default admin distance
• F. It establishes a static route to the 172.16.3.0 network

• C. All switch and bridge ports are in either the forwarding or blocking state
• ^{When a switch first comes up, it will be in the listening and learning states. This is needed so that the switch learns the MAC address of the devices on the LAN, and to learn where any loops in the network may exist. After this initial period, the ports will be forwarding to the hosts or blocking certain ports that create a loop.}

• C. HFD(config)# ip route 10.5.6.0 0.0.0.255 fa0/0, D. HFD(config)# ip route 10.5.4.6 255.255.255.0 10.5.6.0, F. HFD(config)# ip route 10.5.6.0 255.255.255.0 fa0/0
• There are two ways to specify a default static route. One is to specify the interface to use for forwarding packets, like in answer C. The other way is to specify the IP address of the next hop router, as in answer D.

• The following command string is used to add a static route to the routing table:
• ip route [dest network] [mask] [next hop address or exit interface] [administrative distance] [permanent]

• This list describes each command in the string:
• ip route - command to create static route
• destination network - network placed in the routing table
• mask - subnet mask used
• next hop address - next hop router's address that will receive packet and forward to remote network.
• (default admin dist = 1)