CCNA - ENSA 9-12
Describe Class Based Weighted Fair Queueing (CBWFQ).
- Class-Based Weighted Fair Queuing (CBWFQ) extends the standard WFQ functionality to provide support for user-defined traffic classes. - With CBWFQ, you define traffic classes based on match criteria including protocols, access control lists (ACLs), and input interfaces.
Information recorded on the physical topology typically includes what details?
- Device name - Device location (address, room number, rack location) - Interface and ports used - Cable type
Define FIFO queueing.
- In its simplest form, First In First Out (FIFO) queuing buffers and forwards packets in the order of their arrival. - FIFO has no concept of priority or classes of traffic and consequently, makes no decision about packet priority. - There is only one queue, and all packets are treated equally.
Name three techniques to prevent packet loss.
- Increase link capacity (BW) to ease or prevent congestion. - Guarantee enough bandwidth and increase buffer space to accommodate bursts of traffic from fragile flows. WFQ, CBWFQ, and LLQ can guarantee bandwidth and provide prioritized forwarding to drop-sensitive applications. - Drop lower-priority packets before congestion occurs. Cisco IOS QoS provides queuing mechanisms, such as weighted random early detection (WRED), that start dropping lower-priority packets before congestion occurs.
Describe some methods of implementing redundancy in a well designed network.
- Redundant Links - Increase bandwidth with multiple links (Etherchannel) - Dual-multihomed (redundant connections to more than one ISP) - Multiple Devices - FHRPs
Name some helpful show commands for NTP.
- Show NTP associations - Show NTP status - Show clock detail
Place these in the correct order. A. Eliminate possible causes B. Propose hypothesis C. Define the problem D. Test hypothesis E. Analyze information F. Gather information G. Solve the problem
1. Define the problem 2. Gather information 3. Analyze information 4. Eliminate possible causes 5. Propose hypothesis 6. Test hypothesis 7. Solve the problem
To enable CDP globally for all the supported interfaces on the device, enter _________ in the global configuration mode. A. cdp run B. cdp enable C. no cdp enable D. lldp enable E. lldp run
A. cdp run
________________ is applied to inbound traffic on an interface. When the traffic rate reaches the configured maximum rate, excess traffic is dropped. A. Traffic Policing B. Traffic Shaping C. Traffic Alignment D. Traffic Classification
B. Traffic Policing
To enable CDP on the specific interface enter cdp enable command int interface configuration mode. A. cdp run B. cdp enable C. enable cdp D. cdp neighbors E. lldp run
B. cdp enable
Voice can tolerate a certain amount of loss without any noticeable effects. Voice packet loss should be no more than _______. A. 0.01% B. 0.1% C. 1.0% D. 10%
C. 1.0%
Video can tolerate a certain amount of latency. Latency should be no more than _________ (ms). A. 10 B. 30 C. 400 D. 800
C. 400 milliseconds (ms)
Network documentation should include what details?
Common network documentation includes the following: - Physical and logical network topology diagrams - Network device documentation that records all pertinent device information - Network performance baseline documentation
Which OSI layer are you troubleshooting when investigating a spanning-tree loop?
Data Link Layer
The variable amount of time it takes for the frame to travel between the source and destination. A. Code delay B. Packetization delay C. Queuing delay D. Serialization delay E. Propagation delay F. De-jitter delay
E. Propagation delay
Describe the role of the Distribution layer in the three-tiered network model.
It provides intelligent switching, routing, and network access policy functions to access the rest of the network. Routing, QoS, ACLs, etc.
The ____________ does the same thing as CDP, but it is not specific to Cisco devices.
Link Layer Discovery Protocol (LLDP)
Define SNMP
Simple Network Management Protocol
Scalability is the term for a network that can grow without losing availability and reliability. To support a large, medium or small network, the network designer must develop a strategy to enable the network to be available and to scale effectively and easily. What recommendations would you make for a basic network design strategy with scalability in mind?
- Use expandable, modular equipment that can be easily upgraded to increase capabilities. - Design a hierarchical network to include modules that can be added, upgraded, and modified, as necessary. - Create an IPv4 and IPv6 address strategy that is hierarchical. Careful address planning eliminates the need to re-address the network to support additional users. - Use a scalable routing protocol (OSPF) - Implement wireless connectivity to allow for mobility and expansion
Describe Weighted Fair Queueing (WFQ).
- Weighted Fair Queuing (WFQ) is an automated scheduling method that provides fair bandwidth allocation to all network traffic. - WFQ does not allow classification options to be configured. - WFQ applies priority, or weights, to identified traffic and classifies it into conversations or flows.
This field has 6-bits allocated for QoS. Called the ________________ field, these six bits offer a maximum of 64 possible classes of service. A. Differentiated Services Code Point (DSCP) B. IP Precedence (IPP) C. Explicit Congestion Notification (ECN) D. Class or Service (CoS)
A. Differentiated Services Code Point (DSCP)
Regarding SNMP, describe the difference between "get" and "set."
A get request is used by the NMS (network management system) to query the device for data. A set request is used by the NMS to change configuration variables in the agent device.
____________________ are test instruments that are used to directly measure electrical values of voltage, current, and resistance. A. Digital Multimeters B. Cable Testers C. Protocol Analyzers D. Cable Analyzers
A. Digital multimeters (DMMs)
Syslog alarms are separated into levels 0-7. Which is the most severe? A. 0 B. 1 C. 4 D. 7
A. 0 Warning Level 4 - Emergency Level 0: These messages are error messages about software or hardware malfunctions Notification Level 5 Informational Level 6 Debugging Level 7
Voice can tolerate a certain amount of jitter without any noticeable effects. Jitter should be no more than ___________. A. 30 ms B. 50 ms C. 100 ms D. 120 ms
A. 30 ms
Network congestion causes delay. Network congestion points are ideal candidates for QoS mechanisms. Name three examples of typical congestion points.
A. Aggregation B. Speed Mismatch C. LAN to WAN
- This is not really an implementation as QoS is not explicitly configured. - Use this when QoS is not required. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
A. Best Effort Model
Critical data is treated the same as casual email is treated. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
A. Best Effort Model
The model is the most scalable. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
A. Best Effort Model
- Sessions, or flows, are analyzed to determine what traffic class they belong to. - When the traffic class is determined, the packets are marked. A. Classification and marking tools B. Congestion avoidance tools C. Congestion management tools
A. Classification and marking tools
The fixed amount of time it takes to compress data at the source before transmitting to the first internetworking device, usually a switch. A. Code delay B. Packetization delay C. Queuing delay D. Serialization delay E. Propagation delay F. De-jitter delay
A. Code delay
The design facilitates understanding the role of each device at every tier, simplifies deployment, operation, and management, and reduces fault domains at every tier. Which borderless network design guideline is being defined by the above? A. Hierarchical B. Modularity C. Resiliency D. Flexibility
A. Hierarchical - The design facilitates understanding the role of each device at every tier, simplifies deployment, operation, and management, and reduces fault domains at every tier
The chassis on ___________________ accept field-replaceable line cards. A. Modular configuration switches B. Fixed configuration switches C. Stackable configuration switches
A. Modular configuration switches
When a router receives a Real-Time Protocol (RTP) digital audio stream for Voice over IP (VoIP), it must compensate for the jitter that is encountered. The mechanism that handles this function is ______________________. A. Playout delay buffer B. Priority Queue C. Low Latency Queueing D. Class Based Weighted Fair Queueing
A. Playout delay buffer
*Mar 1 11:52:42: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to down Refer to the syslog output. What is the mnemonic for this syslog message? A. UPDOWN B. Interface GigabitEthernet0/0/0 C. 3 D. Link E. *Mar 1 11:52:42
A. UPDOWN
This command tells the device to ignore the startup config file during startup. A. rommon 1 > confreg 0x2142 B. rommon 1 > confreg 0x2102 C. R1(config)# config-register 0x2102 D. R1(config)# config-register 0x2142
A. rommon 1 > confreg 0x2142 The confreg 0x2142 command allows the user to set the configuration register to 0x2142. With the configuration register at 0x2142, the device will ignore the startup config file during startup. You can bypass forgotten passwords this way.
Which OSI layer are you troubleshooting when investigating a DNS related problem?
Application Layer
Voice can tolerate a certain amount of latency, jitter, and loss without any noticeable effects. Latency should be no more than _____________? A. 100 milliseconds (ms) B. 150 milliseconds (ms) C. 200 milliseconds (ms) D. A few days E. It's not D F. 250 milliseconds (ms)
B. 150 milliseconds (ms)
CDP is a Cisco proprietary Layer ___ protocol that is used to gather information about Cisco devices which share the same data link. A. 1 B. 2 C. 3 D. 4 E. 8
B. 2
Voice traffic requires at least ________ Kbps of bandwidth. A. 25 B. 30 C. 100 D. 200
B. 30 kbps
Video can tolerate a certain amount of jitter without any noticeable effects. Jitter should be no more than _________ (ms). A. 5 B. 50 C. 200 D. 500
B. 50 ms
Hardware-based problems are solved using the ______________ approach. A. Divide and Conquer B. Bottom up C. Top Down D. Educated Guess
B. Bottom-up
____________________ are specialized, handheld devices designed for testing the various types of data communication cabling. A. Digital Multimeters B. Cable Testers C. Protocol Analyzers D. Cable Analyzers
B. Cable Testers
- Traffic classes are allotted portions of network resources, as defined by the QoS policy. - The QoS policy also identifies how some traffic may be selectively dropped, delayed, or re-marked. - The primary ____________________ tool is WRED and is used to regulate TCP data traffic in a bandwidth-efficient manner before tail drops caused by queue overflows occur. A. Classification and marking tools B. Congestion avoidance tools C. Congestion management tools
B. Congestion avoidance tools
Which two layers are collapsed in the two-tier model. Pick two. A. Access B. Core C. Distribution D. Bridge E. Link
B. Core C. Distribution Also known as the collapsed core network design
Features and options on _______________ are limited to those that originally come with the switch. A. Modular configuration switches B. Fixed configuration switches C. Stackable configuration switches
B. Fixed configuration switches
There are two primary SNMP manager requests. Pick 2 A. Pull B. Get C. Push D. ACK E. Set
B. Get E. Set There are two primary SNMP manager requests, get and set.
The original IP standard specified the ____________ field to be used for QoS markings at layer 3. It is 3 bits in width. A. Differentiated Services Code Point (DSCP) B. IP Precedence (IPP) C. Explicit Congestion Notification (ECN) D. Class or Service (CoS)
B. IP Precedence (IPP)
- This provides very high QoS to IP packets with guaranteed delivery. - It defines a signaling process for applications to signal to the network that they require special QoS for a period and that bandwidth should be reserved ahead of time. - This can severely limit the scalability of a network. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
B. Integrated Services (IntServ)
Resource intensive due to the stateful architecture requirement for continuous signaling. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
B. Integrated Services (IntServ)
Which QoS model provides per-request policy admission control? A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
B. Integrated Services (IntServ)
The design allows seamless network expansion and integrated service enablement on an on-demand basis. Which borderless network design guideline is being defined in the above sentence? A. Hierarchical B. Modularity C. Resiliency D. Flexibility
B. Modularity - The design allows seamless network expansion and integrated service enablement on an on-demand basis.
_______________ retains excess packets in a queue and then schedules the excess for later transmission over increments of time. The result is a smoothed packet output rate. A. Traffic Policing B. Traffic Shaping C. Traffic Alignment D. Traffic Classification
B. Traffic shaping
IPv4 and IPv6 specify an 8-bit field in their packet headers to mark packets. The ___________ field for IPv4 and the ___________ field for IPv6. (pick 2) A. QoS B. ToS. C. Traffic Class D. CoS E. DSCP F. RSVP
B. Type of Service (ToS) C. Traffic Class
This discovery protocol is cisco proprietary. A. ICMP B. LLDP C. CDP D. NTP E. SNMP
C. Cisco Discovery Protocol
- When traffic exceeds available network resources, traffic is queued to await availability of resources. - Common Cisco IOS-based _______________________ tools include CBWFQ and LLQ algorithms. A. Classification and marking tools B. Congestion avoidance tools C. Congestion management tools
C. Congestion management tools
- Provides many different levels of quality - No absolute guarantee of service quality - Requires a set of complex mechanisms to work in concert throughout the network A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
C. Differentiated Services (DiffServ)
- This provides high scalability and flexibility in implementing QoS. - Network devices recognize traffic classes and provide different levels of QoS to different traffic classes. A. Best Effort Model B. Integrated Services (IntServ) C. Differentiated Services (DiffServ) D. Room Service (RoomServ)
C. Differentiated Services (DiffServ)
_____________________ can investigate packet content while flowing through the network. A. Digital Multimeters B. Cable Testers C. Protocol Analyzers D. Cable Analyzers
C. Protocol analyzers
Software problems are often solved using a ____________ approach. A. Divide and Conquer B. Bottom up C. Top Down D. Educated Guess
C. Top down. Software problems likely reside in the application layer
Cisco devices can send log messages to several different facilities. Name as many as you can.
Cisco devices can send log messages to several different facilities. Event messages can be sent to one or more of the following: Console - Messages log to the console and can be viewed using terminal emulation software Buffered logging - stored in device memory for a limited time SNMP traps - Router events, such as exceeding a threshold, can be processed by the router and forwarded as SNMP traps to an external SNMP manager. Syslog - Cisco devices can be configured to forward log messages to an external syslog service
R1(config)# boot system flash0: isr4200-universalk9_ias.16.09.04.SPA.bin What is the effect of issuing the previous command?
Configures the router to locate and load a new IOS image, the file named isr4200-universalk9_ias.16.09.04.SPA.bin, from NVRAM during the next bootup.
________________ are multifunctional handheld devices that are used to test and certify copper and fiber cables for different services and standards. A. Digital Multimeters B. Cable Testers C. Protocol Analyzers D. Cable Analyzers
D. Cable analyzers
For ethernet traffic, frames are marked in the _________ marking field. A. QoS B. ToS. C. Traffic Class D. CoS E. DSCP F. RSVP
D. CoS QoS Tools: Ethernet (802.1q, 802.1p) Layer: 2 Marking Field: Class of Service (CoS) Width in Bits: 3 (8 possible classifications)
______________ is the variation in the delay of received packets. A. Congestion B. Latency C. Queuing D. Jitter E. Bandwidth
D. Jitter
*Mar 1 11:52:42: %LINK-3-UPDOWN: Interface GigabitEthernet0/0/0, changed state to down Refer to the syslog output. What is the syslog reporting facility? A. UPDOWN B. Interface GigabitEthernet0/0/0 C. 3 D. Link E. *Mar 1 11:52:42
D. Link
Although data traffic is relatively insensitive to drops and delays compared to voice and video, a network administrator still needs to give priority to certain types of data traffic. Put the following in order of priority. A. Mission Critical - Not Interactive B. Not Mission Critical - Not Interactive C. Not Mission Critical - Interactive D. Mission Critical - Interactive
D. Mission Critical - Interactive C. Not Mission Critical - Interactive A. Mission Critical - Not Interactive B. Not Mission Critical - Not Interactive
The fixed amount of time it takes to transmit a frame onto the wire. A. Code delay B. Packetization delay C. Queuing delay D. Serialization delay E. Propagation delay F. De-jitter delay
D. Serialization delay
R1# copy running-config usbflash0: Describe the effect of issuing the above command.
We are using the "copy run usbflash0:/" command to copy the configuration file to a USB flash drive.
To enable LLDP globally on a Cisco network device, enter the _____________ command in the global configuration mode. A. cdp run B. cdp enable C. enable cdp D. lldp enable E. lldp run
E. lldp run
The show cdp neighbors command provides helpful information about each CDP neighbor device, including the following: A. Device identifiers B. Port identifier C. Capabilities list D. Platform E. A, B, C F. All of the above
F. All of the above -Device identifiers - This is the host name of the neighbor device (S1). - Port identifier - This is the name of the local and remote port (G0/0/1 and F0/5, respectively). - Capabilities list - This shows whether the device is a router or a switch (S for switch; I for IGMP is beyond scope for this course) - Platform - This is the hardware platform of the device (WS-C3560 for Cisco 3560 switch).
The fixed amount of time it takes to buffer a flow of packets and then send them out in evenly spaced intervals. A. Code delay B. Packetization delay C. Queuing delay D. Serialization delay E. Propagation delay F. De-jitter delay
F. De-jitter delay
True or False: Traffic should be classified and marked as close to its destination as technically and administratively feasible.
False. Called a trust boundary, traffic should be classified and marked as close to its SOURCE as technically and administratively feasible.
_________________ define the processing capabilities of a switch by rating how much data the switch can process per second.
Forwarding rates
Information recorded on the logical topology typically includes what details?
Information recorded on a logical network topology may include the following: - Device identifiers - IP addresses and prefix lengths - Interface identifiers - Routing protocols / static routes - Layer 2 information (i.e., VLANs, trunks, EtherChannels)
___________________ switches are typically deployed in the core and distribution layers of an organization's switched network.
Multilayer or Layer 3 switches
Which OSI layer are you troubleshooting when investigating a routing protocol loop?
Network Layer
Define NTP and describe why we need it.
Network Time Protocol It is important to synchronize the time across all devices on the network because all aspects of managing, securing, troubleshooting, and planning networks require accurate timestamping. When the time is not synchronized between devices, it will be impossible to determine the order of the events and the cause of an event.
Which OSI layer are you troubleshooting when the cause of network transmission errors is due to late collisions, short frames, and jabber?
Physical Layer
_____________________________ allows the switch to deliver power to a device over the existing Ethernet cabling.
Power over Ethernet (PoE)
Describe the difference between SNMPv1, SNMPv2, and SNMPv3.
SNMPv1 - Offers minimal security SNMPv2 - Offers minimal Security - Allows for bulk retrieval of information SNMPv3 - Operates similarly to SNMPv2 but it secures transmission of critical data between managed devices
R1# copy flash: tftp: Source filename []? isr4200-universalk9_ias.16.09.04.SPA.bin Address or name of remote host []? 172.16.1.100 Destination filename [isr4200-universalk9_ias.16.09.04.SPA.bin]? Writing isr4200-universalk9_ias.16.09.04.SPA.bin... !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! (output omitted) 517153193 bytes copied in 863.468 secs (269058 bytes/sec) What the heck just happened?
The Cisco IOS Software image (isr4200-universalk9_ias.16.09.04.SPA.bin ) backup was saved to a tftp server located at the 172.16.1.100 IP address.
Describe Low Latency Queueing (LLQ).
The Low Latency Queuing (LLQ) feature brings strict priority queuing (PQ) to CBWFQ. PQ allows delay-sensitive packets (voice) to be sent before packets in other queues automatically. LLQ is similar to CBWFQ in that it allows users to define traffic classes in addition to voice traffic being placed in the front of the line automatically.
Describe the relationship between the SNMP agent and the MIB.
The SNMP agent and MIB reside on SNMP client devices. Network devices that must be managed, such as switches, routers, servers, firewalls, and workstations, are equipped with an SNMP agent software module. MIBs store data about the device and operational statistics and are meant to be available to authenticated remote users. MIB = Management Information Base
Cisco IOS QoS includes ________________ as a possible congestion avoidance solution. This algorithm drops traffic early before the buffer is full to prevent tail drops.
Weighted Random Early Detection (WRED)
Describe the role of the Access layer in the three-tiered network model.
The access layer represents the network edge, where traffic enters or exits the campus network. Traditionally, the primary function of an access layer switch is to provide network access to the user.
Describe the role of the Core layer in the three-tiered network model.
The core layer is the network backbone. It connects several layers of the campus network. The core layer serves as the aggregator for all of the distribution layer devices and ties the campus together with the rest of the network. The primary purpose of the core layer is to provide fault isolation and high-speed backbone connectivity.
If there are no boot system commands in the configuration, the router defaults to loading _______________________?
The first valid Cisco IOS image in flash memory.
Log messages should be ______________________ so that when they are sent to another destination, such as a Syslog server, there is record of when the message was generated.
Timestamped
What is the goal of redundancy in network design?
To prevent disruption of network services by minimizing the possibility of a single point of failure.
Which OSI layer are you troubleshooting when investigating an extended ACL related problem?
Transport Layer
SNMP agents generate and send _________ to inform the NMS immediately of certain events. Select the right answer and define the term. A. Alerts B. Notifications C. Syslog messages D. Traps
Traps Traps are unsolicited messages alerting the SNMP manager to a condition or event on the network. Examples of trap conditions include, but are not limited to, improper user authentication, restarts, link status (up or down), MAC address tracking, closing of a TCP connection, loss of connection to a neighbor, or other significant events.
R1# copy tftp running-config Describe the effect of issuing the above command.
We are copying the running config file FROM the TFTP server TO the running-config of the device. To restore the running configuration or the startup configuration from a TFTP server, use either the copy tftp running-config or copy tftp startup-config command
Network bandwidth is measured in the number of bits that can be transmitted in ______________
a single second
A _____________ is the area of a network that is impacted when a critical device or network service experiences problems.
failure domain
A _______________ is used to establish normal network or system performance to determine the "personality" of a network under normal conditions.
network baseline
The __________________ of a switch refers to the number of ports available on a single switch.
port density
A network administrator can use the command ____________ to discover the IP address for a switch, and then remotely access it.
show cdp neighbors detail
With LLDP enabled, device neighbors can be discovered by using the ____________________ command
show lldp neighbors
When more details about the neighbors are needed, the __________________ command can provide information, such as the neighbor IOS version, IP address, and device capability.
show lldp neighbors detail