CCENT Test 2

What two vlans are reserved for system use?

0 and 4095

What are the three switchport configuration options that can always avoid duplex mismatch error between the switches?

1: Set both sides to half-duplex 2: Set one side to autonegotiation and the other to half-duplex. 3:set both sides to auto negotiation On an ehternet connection, a duplex mismatch is acondition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other operates in full duplex. The effect of a duplex mismatch is a link that operates inefficiently. Duplex mismatch may be caused by manually setting two connected network interfaces at different deuplex modes or by connection a device that performs autonegotiation to one that is manually set to a full duplex mode.

If a router has 4 interfaces and each is connected to one of 4 switches, how many broadcast domains are present int he router?

4 Each router interface makes a broadcast domain. Therefore 4 router interfaces = 4 broadcast domains.

On which device is every port in the same collision domain?

A Hub

A workstation has just resolved a browser URL to the IP address of a server. Which protocol will the workstation now use to determine the destination MAC address to be placed into frames directed toward the server?

ARP On ehternet devices use Address REsolution Protocol (ARP) to find Ip address to MAC addresses mapping.

Which feature builds a FIB and an adjancy table to expedite packet forwarding?

Cisco Express Forwarding

Which switching methd duplicates the first six bytes of a frame before making a switching decision?

Cut through switching

Which 3 statements accurately describe layer 2 Ethernet switches? (3) a: Establishing vlans increases the number of broadcast domains. b: Switches that are configured with vlans make forwarding decisions based on both layer 2 and layer 3 address information. c: If a switch receives a frame for an unknown destination, it uses ARP to resolve the address. d: In a property functioning network with redundant switched paths, each switched segment will contain one root bridge with all its ports in the forwarding state. All other switches in that broadcast domain will have only one port. e: Spanning Tree Protocol allows switches to automatically share vlan information.

D, E, and A Microsegmentation is a method for dividing your network using switches. Each switch port is a separate collision domain. Only two nodes are coexisting on each collision domain: one node is the host and the other one is the switch. Microsegmentation increases the number of collision by dividing a large collision domain into smaller collision domains. As result, microsegmentation decreases the number of collisions on the network. Each VLAN is a seperete broadcast domain, and you need a router to communicate among separate broadcast domains, Therefore, establishing vlans increases the number of broadcast domains.

What address type does a switch use to make selective forwarding decisions?

Destination Mac Address Explanation: Layer 2 switches maintain a table of destination MAC addresses and associated ports. When a unicast frame is received, its destination MAC address is searched in the MAC address table. If a match is found the frame is forwarded through the port associated with that destination MAC address. If no entry matches, the frame is flooded out all ports except the receiving port. In brief, the switches forward frames based on destination MAC address.

On which device is every port in the same collision domain?

Hub

What are the first 24 bits in a MAC Address called?

OUI. A Mac Address is 48 bit in binary (12 hexadecimal digits). The first half of the addresses identifies the manufacturer of the card, called the Organizational Unique Identifier (OUI). This code is assigned to each manufacturer by the IEE.

Two commands to determine Trunk connectivity

Show interfaces interface trunk show interfaces interface switchport

What command do you use to see the ports that are assigned to VLAN 20?

Switch#show vlan id 20

Which command can you enter to view the ports that are assigned to VLAN 20?

Switch#show vlan id 20

Which command do you enter to view the ports assigned to vlan 20?

Switch#show vlan id 20

What command can you use to view the ports assigned to VLAN 20?

Switch#show vlan id 20 The show vlan id command displays information about a particular VLAN that is identified by a VLAN ID number, valid values are from 1 to 4094.

What two devices will help solve the problem of a network suffering from a broadcast storm?

a Router and a layer 3 switch

Which are two characteristics of 802.1Q protocol? a: it modifies the 802.3 frame header and this requires that the FCS be recomputed. b: it is a layer 2 protocol messaging protocol which maintains VLAN configurations across networks. c:Its used exclusively for tgging vlan frames and does not address network reconvergence following switched network topology changes. d: It includes an 8-bet field which specifies the priority of a frame. e: IT is a trunking protocol capable a carrying untagged frames.

a: IT modifies the 802.3 frame header and this requires that the FCS be recomputed. e: It is a trunking protocol capable of carrying untagged frames.

Why will a switch never learn a broadcast address?

A broadcast address will never be the source address of a frame.

Which table displayes the MAC Addresses learned on a switch?

CAM table

Which interface counter can you use to diagnose a duplex mismatch problem?

Late Collisions In normal half-duplex operations 'late collisions" do not occur. However, in a duplex mismatch the collisions seen on the half-duplex side of the link are often Late collisions. The full duplex side will usually register FCS (Frame Check Sequence) errors, or runts.

On which OSI layer does a VLAN operate?

Layer 2 VLAN's operate at layer 2 (data link layer) of the OSI model. Administrations often configure a VLAN to map directly to an IP network, or subnet, which gives the appearance of involving layer 3 to the network (the network layer)

Which OSI layer does a vlan operate?

Layer 2 VLANS operate at layer 2 (data link layer) of the OSI model. Admins often configure VLAN to map directly to an IP network, or subnet, which gives the appearance of involving layer 3 (the network layer)

Which layer does a VLAN operate?

Layer 2 VLANs operate at layer 2 (the data link layer) of the OSI model. Administrators often configure a VLAN to map directly so an IP network, or subnet, which gives the appearance of involving Layer 3 (The network Layer)

Late collisions

May indicate a duplex mismatch. By definition, they occur after the 512th bit of the frame has been transmitted.

What I the output of the following set of commands? Router#configure terminal Router(config)#vlan 10 Router(config-vlan)#do show vlan

This adds vlan10 to the database.

What two reasons do the Ethernet protocol use physical addresses?

To uniquely identify devices at layer 2 To allow communication between different devices on the same network.

What would happen if you replaced a hub with a switch in terms of broadcast domains and collision domains?

the number of collision domains would increase and the number of broadcast domains would remain the same. EXPLANATION: Switches increase the number of collision domains, because each switch port is a separate collision domains. On the other hand, switches cannot filter broadcasts (unless you configure VLANS), therefore the number of broadcast domains would remain the same.

Which Mtu Size can cause a baby giant error?

1518 Standard Ethernet Frame = MTU +Header & CRC trailer = 1500 + 18 = 1518 bytes

Why will a swtich never learn a broadcast address?

A broadcast address will never be the source of an address Frame.

VLAN Default

By default, all management traffic )VTP,CDP,DTP,LACP etc) is always sent using NAtive VLAN over trunk. It does not mean the Native VLAN should be VLAN 1 since we can define any LVAN as Native vlan on per trunk port basis.

Which table displays the mac addresses that are learned on a switch?

CAM. Content Addressable Memory (CAM) table is a MAC address table that maps switch ports to the MAC addresses found on those ports.

What two protocols can detect native vlan mismatch errors?

CDP and STP. NAtive VLAN Mismatch the native vlan is used to carry untagged traffic across an 802.1Q trunk. The default native vlan is set to vlan 1, but can be changed on each trunk int. The native vlan must be the same on both sides of a trunk interface. Native vlan mismatch between the two ends of a trunk is a common mistake. Native clan misconfuiguration generates traffic leak between two vlans. Which results in strange forwarding behavior and possible fatal errors in protocols such as Spanning Tree protocol (STP) Cisco Discovery Protcol (CDP) version s2 passes native vlan information between cisco switches and displays a notification if a mismatch is deteceted. Mistmatc messages arc displayed every minutes and they look like the following: #CDP-4-NATIVE VLAN_MISMATCH: Native VLAN mismatch discovered on Fa0/1 Also Spanning Tree Protocol (STP) is able to detect VLAN mismatches and it will place the port in a port VLAN ID (PVID) inconsistent state and will not forward on the link. This will result in notifications such as: %SPANTREE-2-RECV_PVID: Received BPDU with inconsistent peer vlan id 300 on GigabitEthernet/0/25 VLAN100

Which command would you use to view directly connected Cisco DEvices?

CDP run; CDP run To enable CDP globally. cdp enable: To enable CDP on an interface.

Which MAC protocol sets a random timer to reattempt communication?

CSMA/CD

Which feature allows a device to use a switch port that is configured for half duplex to access the network?

CSMA/CD

What MAC protocol sets a random timer to reattempt communication?

CSMA/CD Carrier sense multiple access with collision detection (CSMA/CD) is a media access control method used most notably in early Ethernet technology for local area networking. It uses a carrier sensing scheme in which a transmitting station detects collisions by sensing transmission from other stations while transmitting a frame. When this collision condition is detected, the station stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.

What layer of the OSI model does the protocol that provides the information that is displayed by the show cdp neighbors command operate?

Data Link Layer. The show cdp neighbors command uses CDP to provide information about neighboring connected cisco devices. CDP operates at the Data Link later (layer2)

Which feature facilitates the tagging of frames on a specific VLAN?

Encapsulation

Which feature facilitates the tagging of frames on a specific VLAN?

Encapsulation Two types of frame encapsulations are : ISL - Cisco Proprietary, and 802.1Q - an IEEE standard.

Which 3 fields are contained in a layer 2 Ethernet frame?

Frame Check Sequence Preamble Type/ Length

Full duplex: There are no collisions in full duplex mode. A dedicated switch port is requited for each full duplex node. The host network card and the switch port must be capable of operating in full duplex mode.

Half Duplex - Connections allow devices to either send or receive but not both at the same time and experience collisions which grestly reduce the effective throughput when the network utilization increases. Examples are 10 Base2 and 10Base5 which use single shared cable and 10BaseT using a hub. Hub supports half duplex communication at 10 Mbps because only one of the stations connected to the hub can send data at one time. Collisions do occur when two stations find the wire free and tr to send data at the same time. Full Duplex: Connections require a point to point connection between two devices. For full duplex operation the host needs a full duplex network interface card (NIC), a dedicated switch port operating at full deplux mode and a medium supporting full duplex communication, Ex. UTP/ STP and Cat 5 cable.

Describing leyer 2 Ethernet switches

Micorsegmentation decreases the number of collisions ont he network. In a properly funcitonining network with redundant switched paths, each switched segment will contain one root bridge with all it's ports in the forwarding sate. All other switches in that broadcast domain will have only one root port. Establishing vlans increases the number of broadcast domains. EXPLANATION: Microsegmentation is a method for dividing your network using switches. Each switch port is a separate collision domain. Only two nodes are coexisting on each collision domain: one node is the host and the other is the switch. Microsegmentation increases the number of collision domains by dividing a large collision domain into smaller collision domains. As a result, microsegmentation decreases the number of collisions on the network. Although the LAN switch eliminates collision domains, all hosts connected to the switch are still int he same broadcast domain. Each VLAN is a separate broadcast domain, and you need a router to communicate among separate broadcast domains, Therefore, establishing vlans increases the number of broadcast domains. In a properly functioning network with redundant switched paths, STP blocks redundant paths and creates a loop free network, with one root bridge having all its ports in the forwarding state and all other switches in that segment having only one root port (the port having lowest cost path to the root bridge). These non root switches have other ports in either blocking or forwarding state.

The 3 ways to avoid getting mismatch errors between switches?

Set both sides to auto negotiation. Set both sides to Half-Duplex. set one side to auto negotiation and the other to half duplex.

What command can you enter to determine whether a switch is operating in trunking mode?

Show Interface switchport

What command can you use to assign an interface to the default VLAN?

Switch(config-if)#switchport access vlan 1 In interface config mode, we can use the switchport access vlan command followed by the vlan number to set the VLAN that the interface belongs to. SW(config)#intfa0/2 SW(config-if)#switchport access vlan 1

Why would a newly created application server only have a first ping of 60%?

The Branch router had to resolve the application server MAC address. Before a host can send ICMP Echo (ping) packets to another decide, it needs to learn the MAC address of the destination device. The branch router sends ARP requests on the local LAN to get MAC address of the destination device. In fact, the first ICMP Echo packet is dropped because the router does now know the destination MAC address yet. Once the IP-TO-MAC mapping for Application Server is stored in the ARP cache, the router can send ping requests to the destination without any delay.

What is the reason a first ping to a newly created network only ping 60 % connectivity?

The router had to resolve the appliucation server MAC address.

Which two statements are true statements involving CSMA/CD access method? a: In a CSMA/D collision domain, stations must wait until the media is not in use before transmitting. b:After a collision domain, the station that detected the collision domain has first priority to resend the lost data. c:the use of hubs to enlarge the size of the collision domains is one way to improve the operation of the CSMA/CD access method. d:after a collision, all stations run a random back off algorithm. When the back off delay period has expired, all stations have equal priority to transmit data. e: after a collision, all stations involved run a identical back off algorithm and then synchronize with each other prior to transmitting data. f: in a CSMA/CD collision domain, multiple stations can successfully transmit data at the same time.

a and d. CSMA/CD The algorithm, known as the carrier sense multiple access with collision detection (CSMA/CD) algorithm, defines how the thernet mediums is accessed. CSMA/CD ologic helps prevent collisions and also defines how to act when a collision does occur. When two stations send at the same time a collision occurs. It first occurs on the wire, and then some time elapses before sending stations hear the collision - technically the stations send a few more bits before they actually notice the collision. the CSMA.CD algorithm works thus: 1: A device with a frame to send listens until the Ethernet is not busy. 2:When the Ethernet is not busy, the sender begins sending the frame. 3:The sender listens to make sure that no collision occurred. 4: Once the senders hear the collision, each of them sends a jamming signal to ensure that all stations recognize the collision and stop sending frames. 5: After the jamming is complete, each sender randomizes a timer and waits that long. 6: When each timer expires, the process starts over with Step 1 again. When collisions do occur and the jamming signal is ent, all devices stop sending frames and calculate a random wait time using the back-off algorithm. Each device waits for its calculated wait time and again starts listening to the wire to send it's frames.

Two true statements about Ethernet standards? a:Ethernet is degined by IEEE standard 802.3 b: Ethernet 10BASE-T does not support full-duplex. c: When an Ethernet network uses CSMA/CD, it terminates transmission as soon as a collision occurs. d: When an Ethernet network uses CSMA/CA, it terminates transmission as soon as a collision occurs. Ehternet is defined by IEEE standard 802.2

a:Ethernet is defined by IEEE standard 802.3. c: When an Ethernet network uses CSMA/CD, it terminates trasnsmission as soon as a collision occurs.

A network port interface has 'collision detection' and 'carrier sensing enabled' on a shared twisted pair network. From this statement, what is known about the network interface port? a: This is a 10 Mb/s switch port. b: This is an Ethernet port operating at half duplex. c: This is a port on a network interface card in a PC. d: This is an Ethernet port operating at full duplex. e: This is a 100 Mb/s switch port.

b: This is an Ehternet port operating at half duplex.

Which three fields are contained in a laer 2 Ethernet frame? a: Type/Length b:Preamble c:Frame Check Sequence d: Version 3: TTL

b: preamble a: Type/length c: Frame check Sequence

Which command would you configure globally on a Cicso router that would allow you to view directly connected cisco devices?

cdp run DPS Run: To enable the CDP globally, use the cdp run command in global configuration mode. To disable CDP, use the no form of this command. CDP is enabled by default at the global lvl and oon each supported interface to send or receive CDP information, on cicso devices. CDP enable: To enable Cisco Discovery Protocol (CDP) on an interface, use the cdp enable command in the interface configuration mde. To disable CDP on an interface, use the no form of this command. If CDP is disabled globally, you cannot enable it on each interface using the cdp enable interface configuration mode command