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54 Cards in this Set

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What is the process of examining a network to confirm that it is working as designed?
Verification
What term refers to examining the network to determine what is causing a particular problem so that it can be fixed?
Troubleshooting
Simlet questions might not tell you the enable password, so:
you cannot even look at the configuration, removing the option to simply look at the configuration to find the root of the problem.
The three major troubleshooting processes are as follows:
1. Analyzing – Predict the details of what should happen if the network is working correctly, based on documentation, configuration, and show and debug command output.

2. Problem isolation – determine how far long the expected path the fame/packet goes before it cannot be forwarded any further, again based on documentation, configuration, and show and debug command output.

3. Root cause analysis – identify the underlying causes of the problems identified in the preceding step.
What is CDP?
Cisco Discovery Protocol (CDP) – used to confirm the documentation, and learn about the network topology, to predict normal operation of the network.
What is an advantage of CDP?
CDP discovers basic information about neighboring routers and switches without needing to know the passwords for the neighboring devices.
How does CDP discover information?
To discover information, routers and switches send CDP messages out each of their interfaces. The messages essentially announce information about the device that sent the CDP message.
What are the "show cdp neighbor" outputs?

A R T
B S H I r
A - Capability Codes R - Router
T - Trans Bridge B - Source Route Bridge
S - Switch H - Host I - IGMP
r - Repeater
Devices that can support CDP learn information about others by
by listening for the advertisements sent by other devices.
What devices use CDP?
Switches and Routers
On media that support multicasts at the data link layer, CDP uses ____ frames; on other media, CDP ______.
multicast, sends a copy of the CDP update to any known data link addresses
CDP discovers several useful details from the neighboring Cisco devices. Name six:
1. Device identifier – typically the hostname
2. Address list – network and data link addresses
3. Local interface – the interface on the device issuing the "show cdp" command that neighbor was discovered on.

4. Port identifier – text that identifies the port used by the neighbor to send CDP message to the local device.

5. Capabilities list – information on what type of device it is (for instance, a router or switch)

6. Platform – the model and OS level running in the device
What is a disadvantange to CDP?
CDP creates a security exposure where enabled. Best to use when needed, then keep disabled.
What does the "show cdp" provide?
"show cdp" shows you the CDP timer and CDP holdtimes.
What is a CDP timer?
CDP timers determine how often to send CDP packets
What is CDP holdtime?
CDP holdtime determines how long can you retain those packets.
What is the command in global exec mode sets the CDP timer?
CDP timer <timer in sec>
What is the command in global exec mode sets the CDP holdtime?
CDP holdtime <timer in sec>
How do you turn off all CDP on a router?
global config mode "no cdp run"
How do you turn off CDP on a particular interface or port?
"no cdp enable" on interface config mode
What CDP commands shows you IP address, Hostname and IOS version of attached devices?
"show cdp neighbor details" or "show cdp entry * "
What CDP command shows you the IP address of attached devices?
"show cdp entry * protocol"
What CDP command shows you the IOS version of attached devices?
"show cdp entry * version"
What CDP command shows you the cdp timer and holdtime packets sent and recevied as well as cdp errors?
"show cdp traffic"
What CDP command shows you the sent and received cdp packets as well as the encapsulation method and the layer 1 and 2 status of an interface?
"show cdp interface"
What do the switch "show interfaces" and "show interfaces description" commands do?
List the two code status just like routers.

1. The two codes are named line status and protocol status.

2. They generally refer to whether Layer 1 is working (line status) and whether Layer 2 is working (protocol status).
What's going on if an interface shows as Administratively down?
The interface is configured with the Shutdown command
What's going on if an interface's:

Line Status is down
Protocol Status is down
Interface Status is notconnect
No cable; bad cable; wrong cable pinouts; the speeds are mismatched on the two connected devices; the device on the other end of the cable is powered off or the other interface is Shutdown
What's going on if an interface's:

Line Status is up
Protocol Status is down
Interface Status is notconnect
An up/down state is NOT expected on Switch interfaces
What's going on if an interface's:

Line Status is down
Protocol Status is down (err-disabled)
Interface Status is err-disabled
Port security has disabled the interface
What's going on if an interface's:

Line Status is up
Protocol Status is up
Interface Status is connect
The interface is working
Configuring both speed and duplex on a switch interface disables what?
disables the
IEEE standard autonegotiation process on that interface
When the IEEE autonegotiation process works on both devices, both devices agree to the _____ speed supported by both devices.
fastest
If it's supported by both devices, the will both use what mode?
full-duplex
If full-duplex is not supported on both devices, what speed will they use?
Half-duplex
When one device has disabled autonegotiation, and the other device uses autonegotiation, what will the device using autonegotiation do?
chooses the default duplex settings based on the current speed. The defaults are as follows:
1. If the speed is not known, use 10 Mbps, half duplex.
2. If the speed is somehow known to be 10 or 100 Mbps, default to use half duplex.
3. If the speed is somehow known to be 1000 Mbps, default to use full duplex.
Ethernet interfaces using speeds faster than ____ always use full duplex.
1 Gbps
Switches can automatically sense the speed used by the device on the other end of the cable, and can use that speed based on the _____ signals on the cable.
electrical
Finding a duplex mismatch can be much more difficult than finding a speed mismatch, because:
If the duplex settings do not match on the ends of the Ethernet segment, the switch interface will still be in the connect (up/up) state.
What happens when a Switch is in the (up/up) state, BUT there is a duplex mismatch?
1. In this case, the interface works, but it may work poorly, with poor
performance, and with symptoms of intermittent problems.

2. Half duplex uses CSMA/CD logic, waiting to send and receive a frame, believing collisions occur when they physically do not.
If a LAN design follows cabling guidelines, all collisions should occur by the end of the ____ of any frame.
64th byte
When a switch has already sent 64 bytes of a frame, and the switch receives a frame on that same interface, the switch senses a ______.
collision
Jabber refers to cases in which:
the NIC ignores Ethernet rules and sends frame after frame without a break in between the frames.
An incrementally late collisions counter typically means one of two things:
1. The interface is connected to a collision domain whose cabling exceeds Ethernet cable length standards.

2. The interface is using half duplex, and the device on the other end of the cable is using full duplex.
What are the symptoms in Counter values of excessive noise ?

Causes?
Counter values show Many input errors, but few collisions.

Caused by wrong cables, damaged cables, EMI
What are the symptoms in Counter values of Collisions?

Causes?
Counter values show that more than .1% of all frames are collisions.

Caused by duplex mismatch, jabber, DoS attack
What are the symptoms in Counter values of Late Collisions?

Causes?
Counter values show increasing late collisions

Caused by collision domain or single cable being too long, duplex mismatch
The VLAN switch forwarding logic can be summarized as follows:
1. Determine the VLAN in which the frame should be forwarded. On access interfaces, this is based on the access VLAN associated with the incoming interface.

2. Look for the frame’s destination MAC address in the MAC address table, but only for entries in the VLAN identified in step 1.
When VLAN switch forwarding, if destination MAC is Found (unicast):
forward the frame out the only interface listed in
the matched address table entry
When VLAN switch forwarding, if destination MAC is Not Found (unicast),
flood the frame out all other access ports
(except the incoming port) in that same VLAN
When VLAN switch forwarding, if destination MAC is Broadcast or multicast:
flood the frame out all other access ports
(except the incoming port) in that same VLAN.
The _____ state is the same as administratively down and down.
disabled
When using the "protect" or "restrict" violation action configured, the switch does what?
Discards the offending traffic, but leaves the port in a connect (up/up) state
If there is a dynamic entry of a MAC address and a port, but yet another frame is received in another port with the same MAC, the frame will likely...
be flooded on all other interfaces unless there’s a static entry in the MAC address table. The new source port will add its entry to the MAC table.