Network Addressing and Basic Troubleshooting Module 7 – 8 Checkpoint Test Online

Hint

Duplex mismatches are typically caused by a misconfigured interface or, in rare instances, by a failed autonegotiation. Duplex mismatches may be difficult to troubleshoot because the communication between devices still occurs.

Hint

When changes are made to the running-config file, it should be saved to NVRAM as the startup configuration file in case the router is restarted or loses power. The following command saves the configuration to NVRAM: copy running-config startup-config

Hint

The data that is transmitted over the network can flow using one of three modes: Simplex – Data can only flow in one direction. Half-duplex – Data flows in one direction at a time. Full-duplex – Data flows in both directions at the same time.

Hint

The first action to take place when a switch is powered on is the POST or power-on self-test. POST performs tests on the CPU, memory, and flash in preparation for loading the boot loader.

Hint

Place the options in the following order:

ping	tests end-to-end connectivity between hosts
netstat	displays network connections
tracert	displays the route that is taken to the destination
ipconfig	displays IP settings on host
nslookup	asks the name server for information on the destination domain

Hint

Full-duplex communication allows both ends to transmit and receive simultaneously, offering 100 percent efficiency in both directions for a 200 percent potential use of stated bandwidth. Half-duplex communication is unidirectional, or one direction at a time. Gigabit Ethernet and 10 Gb/s NICs require full duplex to operate, and do not support half-duplex operation.

Hint

In-band configuration requires at least one interface to be active and configured with an IP address to allow for Telnet and SSH connections. AUX and console connections are out-of-band connection methods that do not require any networking services to be configured. CLI is used to configure devices, but does not provide access.

Hint

With out-of-band management, the only requirement is to have a computer directly connected to the console port of the device. This is the primary method to configure a new device because no network connection or prior configurations on the device is required.

Hint

Duplex mismatch is one of the most common causes of performance issues on 10/100 Mbps Ethernet links. It occurs when one port on the link operates at half-duplex while the other port operates at full-duplex

Hint

If a router cannot locate the startup-config file in NVRAM it will enter setup mode to allow the configuration to be entered from the console device.

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If Layers 1 through 3 appear to be operating successfully and the devices can ping the web server, the firewall settings should be checked to determine if the web traffic to the server is permitted.

Hint

Normally, the closer a wireless NIC is to an access point, the faster the connectivity. This problem does not require the network password to be reissued. The combination of the low bandwidth and the intermittent connectivity is pointing towards a weak signal or interference from outside sources.

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The default gateway IP address must be in the same network as the host in order for the host and router to communicate with each other. Because this is a DHCP client, the IP configuration is provided by the DHCP. Thus the DHCP configuration should be checked and corrected.

Hint

The command ipconfig /release will release the current DHCP binding. Ipconfig /renew will request fresh configuration information from the DHCP server. After these two commands are issued, if the workstation is unable to obtain a valid IP configuration from the DHCP server, it could be that there is no network connectivity or the DHCP server is not operational.

Hint

Documentation of all steps taken in troubleshooting, even the ones that did not solve the issue, is a valuable reference should the same or similar problem occur again. Good documentation can save hours of trying to remember how a problem was fixed in the past.

Hint

When troubleshooting a single wireless client, take into consideration all the things a client needs to join and use the network including the following: – The client must be within RF range of an AP and requests to authenticate. – The client authenticates. – The client requests and receives an IP address.

Hint

The laptop could be using an older NIC that uses a protocol not supported by the network. This would be especially likely if the wireless router was not configured in mixed mode. In addition, the wireless router could have SSID broadcasting deactivated. In either case, the computer would not be able to discover the network name. An IP address or workgroup configuration is not required to see the network name.

Hint

For PC1 to be able to communicate with hosts on the other networks, it needs to have an IP address in the same network as the gateway to which it is connected. Its current address of 10.100.1.10/16 is not within the 10.10.0.0/16 network of the gateway interface on R1 (address 10.10.1.1/16).

Hint

The ping utility tests end-to-end connectivity between the two hosts. However, if the message does not reach the destination, there is no way to determine where the problem is located. On the other hand, the traceroute utility (tracert in Windows) traces the route a message takes from its source to the destination. Traceroute displays each hop along the way and the time it takes for the message to get to that network and back.

Hint

A wireless laptop normally does not have an antenna attached unless a repair has recently been implemented. If the wireless NIC is enabled, the correct media, radio, will be used. When the NIC detects an access point, the correct frequency is automatically used.

Hint

The store-and-forward frame forwarding method receives the entire frame and computes the CRC, based on the number of bits (1s) in the frame, to determine whether the received frame has an error. This method is required for QoS analysis on converged networks where frame classification for traffic prioritization is necessary.

Hint

A straight-through cable can be used to connect a computer or a router to a switch. A rollover cable can be used to access a router or switch console line. A coaxial cable is not used any longer in Ethernet networks, but can be found in video connections. A crossover cable can be used to connect a switch to a switch, a computer to a computer, and a router to a router.

Hint

There are three major steps to the router boot sequence:

1. Perform Power-On-Self-Test (POST)
2. Load the IOS from Flash or TFTP server
3. Load the startup configuration file from NVRAM