CCNA 2 v6 RSE Chapter 5 Exam Online

The port speed LED indicates that the port speed mode is selected. When selected, the port LEDs will display colors with different meanings. If the LED is off, the port is operating at 10 Mb/s. If the LED is green, the port is operating at 100 Mb/s. If the LED is blinking green, the port is operating at 1000 Mb/s.

The boot system command is used to set the BOOT environment variable. The config-register and confreg commands are used to set the configuration register. The boot loader command supports commands to format the flash file system, reinstall the operating system software, and recover from a lost or forgotten password.

The switch boot loader environment is presented when the switch cannot locate a valid operating system. The boot loader environment provides a few basic commands that allows a network administrator to reload the operating system or provide an alternate location of the operating system.

The show interfaces command is useful to detect media errors, to see if packets are being sent and received, and to determine if any runts, giants, CRCs, interface resets, or other errors have occurred. Problems with reachability to a remote network would likely be caused by a misconfigured default gateway or other routing issue, not a switch issue. The show mac address-table command shows the MAC address of a directly attached device.

The partial output shows that there are 50 giants (frames longer than the allowed maximum) that were injected into the network, possibly by a malfunctioning NIC. This conclusion can be drawn because there are only 25 collisions, so not all the 50 giants are the result of a collision. Also, because there 25 collisions, it is most likely that not all hosts are using full-duplex mode (otherwise there would not be any collisions). There should be no cabling issues since the CRC error value is 0. There are 0 runts, so the collisions have not caused malformed frames to occur that are shorter than 64 bytes in length .

Escalating CRC errors usually means that the data is being modified during transmission from the host to the switch. This is often caused by high levels of electromagnetic interference on the link.

Full-duplex communications do not produce collisions. However, collisions often occur in half-duplex operations. When a connection has two different duplex configurations, the half-duplex end will experience late collisions. Collisions are found on Ethernet networks. Serial interfaces use technologies other than Ethernet.

SSH provides security for remote management connections to a network device. SSH does so through encryption for session authentication (username and password) as well as for data transmission. Telnet sends a username and password in plain text, which can be targeted to obtain the username and password through data capture. Both Telnet and SSH use TCP, support authentication, and connect to hosts in CLI.

Port security cannot be enabled globally. All active switch ports should be manually secured using the switchport port-security command, which allows the administrator to control the number of valid MAC addresses allowed to access the port. This command does not specify what action will be taken if a violation occurs, nor does it change the process of populating the MAC address table.

In port security implementation, an interface can be configured for one of three violation modes:
Protect – a port security violation causes the interface to drop packets with unknown source addresses and no notification is sent that a security violation has occurred.
Restrict – a port security violation causes the interface to drop packets with unknown source addresses and to send a notification that a security violation has occurred.
Shutdown – a port security violation causes the interface to immediately become error-disabled and turns off the port LED. No notification is sent that a security violation has occurred.

When a violation occurs on a switch port that is configured for port security with the shutdown violation action, it is put into the err-disabled state. It can be brought back up by shutting down the interface and then issuing the no shutdown command.

The default mode for a port security violation is to shut down the port so the switchport port-security violation command is not necessary. The switchport port-security command must be entered with no additional options to enable port security for the port. Then, additional port security options can be added.

The Port Security line simply shows a state of Enabled if the switchport port-security command (with no options) has been entered for a particular switch port. If a port security violation had occurred, a different error message appears such as Secure-shutdown. The maximum number of MAC addresses supported is 50. The Maximum MAC Addresses line is used to show how many MAC addresses can be learned (2 in this case). The Sticky MAC Addresses line shows that only one device has been attached and learned automatically by the switch. This configuration could be used when a port is shared by two cubicle-sharing personnel who bring in separate laptops.

Interface FastEthernet 0/1 is configured with the violation mode of protect. If there is a violation, interface FastEthernet 0/1 will drop packets with unknown MAC addresses.

The violation mode can be viewed by issuing the show port-security interface <int> command. Interface FastEthernet 0/1 is configured with the violation mode of protect. If there is a violation, interface FastEthernet 0/1 will drop packets with unknown MAC addresses.

The steps are:
1. execute POST
2. load the boot loader from ROM
3. CPU register initializations
4. flash file system initialization
5. load the IOS
6. transfer switch control to the IOS

The login and password cisco commands are used with Telnet switch configuration, not SSH configuration.

The network administrator can check the interface status by issuing the show interfaces command. The first status represents the Layer 1 connection status and the second, the layer 2 connection status. The up status means that everything is functioning properly at that layer. The administratively down status means that the network administrator has issued a shutdown command.