ICND1 Chapter 10
Terms in this set (38)
What are the three major steps in troubleshooting in the ICND1 Official Cert Guide?
Step 1. Analyzing/predicting normal operation: Predict the details of what should happen if the network is working correctly, based on documentation, configuration, and show and debug command output. Step 2. Problem isolation: Determine how far along the expected path the frame/packet goes before it cannot be forwarded any farther, again based on documentation, configuration, and show and debug command output.
Step 3. Root cause analysis: Identify the underlying causes of the problems identified in the preceding step—specifically, the causes that have a specific action with which the problem can be fixed.
Cisco Discovery Protocol (CDP)
Used to confirm the documentation, and learn about the network topology, to predict normal operation of the network.
What are some details provided via CDP of neighboring Cisco devices?
• Device identifier: Typically the host name • Address list: Network and data link addresses
• Port identifier: The interface on the remote router or switch on the other end of the link that sent the CDP advertisement
• Capabilities list: Information on what type of device it is (for example, a router or a switch)
• Platform: The model and OS level running on the device
Show cdp neighbors [type number] command
Lists one summary line of information about each neighbor, or just the neighbor found in a specific interface if an interface was listed.
Show cdp neighbors detail command
List one large set (approximately 15 lines) of information, one set for every neighbor
Show cdp entry name command
List the same information as the show cdp neighbors detail command, but only for the named neighbor (case sensitive)
no cdp enable/cdp enable commands
Disables or enables CDP on specific interfaces
no cdp run/cdp run command
Disables or enables CDP for an entire switch
show cdp command
States whether CDP is enabled globally, and lists the default update and holdtime timers.
show cdp interface [type number] command
States whetere CDP is enabled on each interface, or a single interface if the interface is listed, and states update and holdtime timers on those interfaces.
show cdp traffic command
Lists global statistics for the number of CDP advertisements sent and received.
What is the two-code status presented when entering the commands "show interfaces" or "show interfaces description"
The line status and protocol status. They generally refer to whether Layer 1 is working (line status) and whether Layer 2 is working (protocol status), respectively. LAN switch interfaces typically show an interface with both codes with the same value, either "up" or "down."
With the "show interfaces status" command what are some of the single interface status codes presented?
disabled, nonconnected, err-disabled, connected
If an interface's duplex settings have it as "full" instead of "a-full" what is the difference?
Full means the ports is manually running at full duplex while a-full means the port is running at full duplex via autonegotiation
Frames that did not meet the minimum frame size requirement (64 bytes, including the 18byte destination MAC, source MAC, Type, and FCS). Can be caused by collisions.
Frames that exceed the maximum frame size requirement (1518 bytes, including the 18byte destination MAC, source MAC, Type, and FCS).
A total of many counters, including runts, giants, no buffer, CRC, frame, overrun, and ignored counts.
Received frames that did not pass the FCS math; can be caused by collisions. Frame: Received frames that have an illegal format, for example, ending with a partial byte; can be caused by collisions.
Total number of packets (frames) forwarded out the interface
Total number of packets (frames) that the switch port tried to transmit, but for which some problem occurred.
Counter of all collisions that occur when the interface is transmitting a frame.
The subset of all collisions that happen after the 64th byte of the frame has been transmitted. (In a properly working Ethernet LAN, collisions should occur within the first 64
bytes; late collisions today often point to a duplex mismatch.)
Show mac address-table exec command
Displays the contents of a switch's MAC address table
Show mac address-table dynamic exec command
Displays a swith's mac address table, but only learned mac addresses instead of learned and static
show vlan brief and show vlan commands
Lists each VLAN and all interfaces assigned to that VLAN (but does not include operational trunks)
show vlan id num command
Lists both access and trunk ports in the VLAN
show interfaces type number switchport command
Identifies the interface's access VLAN and voice VLAN, plus the configures and operational mode (access or trunk)
show vlan command
List all VLANs known to the switch
show vtp status command
Displays the current vtp mode of a switch
Show interfaces trunk
Shows a trunk port's operational state
Imagine that a switch connects through an Ethernet cable to a router, and the router's host name is Hannah. Which of the following commands could tell you information about the IOS version on Hannah without establishing a Telnet connection to Hannah? (Choose two answers.)
a. show neighbors Hannah
b. show cdp
c. show cdp neighbors
d. show cdp neighbors Hannah
e. show cdp entry Hannah
f. show cdp neighbors detail
E and F. CDP discovers information about neighbors. show cdp gives you several options that display more or less information, depending on the parameters used.
A switch is cabled to a router whose host name is Hannah. Which of the following CDP commands could identify Hannah's model of hardware? (Choose two answers.)
a. show neighbors
b. show neighbors Hannah
c. show cdp
d. show cdp interface
e. show cdp neighbors
f. show cdp entry Hannah
E and F. The show cdp neighbors command lists one line of output per neighbor. However, it does list the platform information of the neighbor, which typically includes the hardware model number. The show cdp entry Hannah command lists a group of messages about the neighboring router, including more detail about the hardware model and the IOS version.
The output of the show interfaces status command on a 2960 switch shows interface Fa0/1 in a "disabled" state. Which of the following is true about interface Fa0/1? (Choose three answers.)
a. The interface is configured with the shutdown command.
b. The show interfaces fa0/1 command will list the interface with two status codes of administratively down and line protocol down.
c. The show interfaces fa0/1 command will list the interface with two status codes of up and down.
d. The interface cannot currently be used to forward frames.
e. The interface can currently be used to forward frames.
A, B, and D. The disabled state in the show interfaces status command is the same as an "administratively down and down" state shown in the show interfaces command. The interface must be in a connected state (per the show interfaces status command) before the switch can send frames out the interface.
Switch SW1 uses its Gigabit 0/1 interface to connect to switch SW2's Gigabit 0/2 interface. SW2's Gi0/2 interface is configured with the speed 1000 and duplex full commands. SW1 uses all defaults for interface configuration commands on its Gi0/1 interface. Which of the following are true about the link after it comes up? (Choose two answers.)
a. The link works at 1000 Mbps (1 Gbps).
b. SW1 attempts to run at 10 Mbps because SW2 has effectively disabled IEEE standard autonegotiation.
c. The link runs at 1 Gbps, but SW1 uses half-duplex and SW2 uses full-duplex.
d. Both switches use full-duplex.
A and D. SW2 has effectively disabled IEEE standard autonegotiation by configuring both speed and duplex. However, Cisco switches can detect the speed used by the other device, even with autonegotiation turned off. Also, at 1 Gbps, the IEEE autonegotiation standard says to use full-duplex if the duplex setting cannot be negotiated, so both ends use 1 Gbps, full-duplex.
The following line of output was taken from a show interfaces fa0/1 command: Full-duplex, 100Mbps, media type is 10/100BaseTX Which of the following are true about the interface? (Choose two answers.)
a. The speed was definitely configured with the speed 100 interface subcommand.
b. The speed might have been configured with the speed 100 interface subcommand.
c. The duplex was definitely configured with the duplex full interface subcommand.
d. The duplex might have been configured with the duplex full interface subcommand.
B and D. The show interfaces command lists the actual speed and duplex setting, but it does not imply anything about how the settings were configured or negotiated. The show interfaces status command lists a prefix of a- in front of the speed and duplex setting to imply that the setting was autonegotiated, leaving off this prefix if the setting was configured.
Which of the following commands list the MAC address table entries for MAC addresses configured by port security? (Choose two answers.)
a. show mac address-table dynamic
b. show mac address-table
c. show mac address-table static
d. show mac address-table port-security
B and C. IOS adds MAC addresses configured by the port security feature as static MAC addresses, so they do not show up in the output of the show mac address-table dynamic command. show mac address-table port-security is not a valid command.
On a Cisco Catalyst switch, you issue a show mac address-table command. Which of the following answers list information you would likely see in most lines of output? (Choose two answers.)
a. A MAC address
b. An IP address
c. A VLAN ID
d. Type (broadcast, multicast, or unicast)
A and C. The show mac address-table command lists all entries in the switch's MAC address table, including dynamically learned and statically defined addresses. From left to right, the output lists the VLAN ID, the MAC address, the type (static or dynamic), and the associated ports (out which frames sent to the listed address will be forwarded by this switch).
Layer 2 switches SW1 and SW2 connect through a link, with port G0/1 on SW1 and port G0/2 on SW2. The network engineer wants to use 802.1Q trunking on this link. The show interfaces g0/1 switchport command on SW1 shows the output listed here:
SW1# show interfaces gigabit0/1 switchport
Administrative Mode: trunk
Operational Mode: trunk
Which of the following must be true on switch SW2's G0/2 port?
a. The operational state per the show interfaces switchport command must be "trunk."
b. The administrative state per the show interfaces switchport command must be "trunk."
c. SW2 must use the switchport mode trunk configuration command on G0/2, or the link will not use trunking.
d. SW2 can use the switchport mode dynamic auto configuration command as one option to make the link use trunking.
D. The show interface switchport command lists a switch's configured value of the switchport mode command as the administrative mode, telling us that SW1 uses the switchport mode trunk configuration command. The operation state shows the current working state (trunk). Of the four answers, one incorrect answer claims that SW2's operational state must also be "trunk"; however, one switch can use trunking, while the other does not. Another answer claims that the administrative mode must be "trunk," which basically means that the command switchport mode trunk must be used. However, SW2 has a few other configuration options that would work, like the switchport mode dynamic desirable and switchport mode dynamic auto commands. The correct answer refers to one of these commands that would work correctly.
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