Podcast
Questions and Answers
What is the primary purpose of autonegotiation as mandated by the IEEE 802.3ab standard?
What is the primary purpose of autonegotiation as mandated by the IEEE 802.3ab standard?
Which command is used to display and modify entries in the ARP cache?
Which command is used to display and modify entries in the ARP cache?
What should be verified in the case of a VLAN assignment issue?
What should be verified in the case of a VLAN assignment issue?
What can result from missing or misconfigured default gateways?
What can result from missing or misconfigured default gateways?
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Which command would you use on a Windows PC to verify the default gateway setting?
Which command would you use on a Windows PC to verify the default gateway setting?
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How can you change the VLAN assignment of a specific port in a network switch?
How can you change the VLAN assignment of a specific port in a network switch?
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What type of problems can arise from duplex mismatches in a network?
What type of problems can arise from duplex mismatches in a network?
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Why is verifying the ARP cache important during troubleshooting?
Why is verifying the ARP cache important during troubleshooting?
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What must be ensured when applying an ACL to avoid misconfigurations?
What must be ensured when applying an ACL to avoid misconfigurations?
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How should entries in an ACL be ordered to minimize misconfigurations?
How should entries in an ACL be ordered to minimize misconfigurations?
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What is a common cause of ACL misconfigurations in relation to IPv4 addresses?
What is a common cause of ACL misconfigurations in relation to IPv4 addresses?
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What issue can arise when the established keyword is applied incorrectly in an ACL?
What issue can arise when the established keyword is applied incorrectly in an ACL?
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What challenge do BOOTP and DHCP face when functioning over a NAT router?
What challenge do BOOTP and DHCP face when functioning over a NAT router?
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What are the two types of network topology diagrams?
What are the two types of network topology diagrams?
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What should network device documentation include?
What should network device documentation include?
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What is a primary purpose of establishing a network baseline?
What is a primary purpose of establishing a network baseline?
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What type of data should be collected for establishing a network baseline?
What type of data should be collected for establishing a network baseline?
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Which of the following is NOT a benefit of having a network baseline?
Which of the following is NOT a benefit of having a network baseline?
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In setting a network performance baseline, it is essential to start with:
In setting a network performance baseline, it is essential to start with:
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What is one consequence of not establishing a network baseline?
What is one consequence of not establishing a network baseline?
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What element does NOT typically belong in comprehensive network device documentation?
What element does NOT typically belong in comprehensive network device documentation?
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Establishing a network baseline helps in determining:
Establishing a network baseline helps in determining:
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Why is it important to maintain accurate network documentation?
Why is it important to maintain accurate network documentation?
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What is a common symptom of general network issues?
What is a common symptom of general network issues?
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Which problem is specifically related to Layer 1 issues?
Which problem is specifically related to Layer 1 issues?
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What factor can make optimization issues particularly difficult to diagnose?
What factor can make optimization issues particularly difficult to diagnose?
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What is a key approach to troubleshooting connectivity issues?
What is a key approach to troubleshooting connectivity issues?
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What should be checked to identify neighbor issues?
What should be checked to identify neighbor issues?
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Why can determining a network layer problem take time?
Why can determining a network layer problem take time?
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What is a likely consequence of missing routes in the routing table?
What is a likely consequence of missing routes in the routing table?
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What is a potential outcome of not addressing environmental problems in network troubleshooting?
What is a potential outcome of not addressing environmental problems in network troubleshooting?
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Which of the following is NOT a symptom of a network layer network problem?
Which of the following is NOT a symptom of a network layer network problem?
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What could signal a problem with the topology database?
What could signal a problem with the topology database?
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What should be the minimum duration for capturing data for analysis?
What should be the minimum duration for capturing data for analysis?
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Which of the following factors should be considered when selecting variables for data analysis?
Which of the following factors should be considered when selecting variables for data analysis?
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How often should an annual analysis of the entire network be conducted?
How often should an annual analysis of the entire network be conducted?
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What is a recommended maximum duration for capturing data unless long-term trends need to be measured?
What is a recommended maximum duration for capturing data unless long-term trends need to be measured?
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Which devices are typically monitored in a logical network topology according to the discussed steps?
Which devices are typically monitored in a logical network topology according to the discussed steps?
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What should follow after starting with a simple data selection process?
What should follow after starting with a simple data selection process?
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How often should baseline measurements be conducted on different sections of the network?
How often should baseline measurements be conducted on different sections of the network?
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What is a common pitfall when selecting too many data points for analysis?
What is a common pitfall when selecting too many data points for analysis?
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What is the typical adequate duration for a baseline capture of data?
What is the typical adequate duration for a baseline capture of data?
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Which of the following is NOT mentioned as a step in identifying devices and ports of interest?
Which of the following is NOT mentioned as a step in identifying devices and ports of interest?
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Study Notes
Troubleshooting IP Connectivity
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Duplex Mismatches: Gigabit Ethernet and most Fast Ethernet NICs use autonegotiation for speed and duplex. Problems can occur if there is a duplex mismatch.
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Local Network Addressing: The
arp
command in Windows displays and modifies entries in the ARP cache, which stores IPv4 addresses and their resolved Ethernet physical (MAC) addresses. -
VLAN Assignment: Ensure devices are in the correct VLAN. For example, a device connected to FastEthernet0/1 should be in VLAN 10 instead of VLAN 1.
-
Default Gateway: A misconfigured or missing default gateway can cause connectivity issues. Use commands like
show ip route
on routers androute print
ornetstat -r
on PCs to verify default gateways.
Network Documentation
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Physical vs. Logical Topology: Network topology diagrams are classified as either physical or logical, showing the physical connection of devices or the logical flow of data, respectively.
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Device Documentation: Network device documentation should include accurate and up-to-date records of network hardware and software, encompassing all pertinent information about the devices. End-system documentation should also be maintained.
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Network Baseline: A network baseline is used to establish normal network performance to understand the network's typical behavior. It provides insight into whether the current network design can meet business requirements and reveal areas of congestion or underutilization.
Data Measurement
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Network Failure: Network failures are usually noticed quickly by users and administrators and are critical to productivity. These involve a subset of users, applications, destinations, or a type of traffic.
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Suboptimal Performance: Optimization issues are harder to detect and diagnose because they can involve multiple layers or even a single host computer. Determining if the issue is a network layer problem can take time.
Network Layer Troubleshooting
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General Network Issues: Check for recent changes in the network topology. Investigate equipment and connectivity problems, including power issues, environmental conditions, and Layer 1 problems such as cabling faults, bad ports, and ISP issues.
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Routing Table: Verify that the routing table is as expected, ensuring there are no missing or unexpected routes.
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Neighbor Issues: Check if routers are properly forming neighbor adjacencies.
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Topology Database: Examine the topology database for any missing or unexpected entries.
Transport Layer Troubleshooting - ACLs
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ACL Misconfigurations:
- Traffic Flow Selection: Ensure that ACLs are applied to the correct interface in the right direction.
- Order of Access Control Entries: The entries should be ordered from specific to general.
- Implicit Deny Any: The "implicit deny any" can cause problems if misconfigured.
- Complex IPv4 Wildcard Masks: While efficient, complex IPv4 wildcard masks are more prone to errors.
- Transport Protocol Selection: Make sure only the correct transport layer protocol is specified.
- Source and Destination Ports: Verify that inbound and outbound ports are correctly specified.
- Established Keyword: Misusing the "established" keyword can lead to unexpected outcomes.
- Uncommon Protocols: ACL misconfigurations can affect protocols other than TCP and UDP.
Transport Layer Troubleshooting - NAT for IPv4
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BOOTP and DHCP: NAT requires valid source and destination IPs. BOOTP and DHCP packets can have difficulty over a router running static or dynamic NAT due to the source IP being 0.0.0.0. Configuring the IPv4 helper feature can resolve this.
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DNS: A DNS server outside a NAT router might not have an accurate view of the internal network.
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Description
Test your knowledge on troubleshooting IP connectivity issues, including duplex mismatches, VLAN assignment, and default gateway configurations. Additionally, explore essential network documentation concepts such as physical and logical topology. This quiz will enhance your understanding of fundamental networking principles.