Network Troubleshooting 15 Flashcards
What is a troubleshooting model
A standardized step by step approach to the troubleshooting process.
Serves as a framework for correcting a problem on a network without introducing further problems or making unnecessary modifications to the network.
What is troubleshooting
The recognition, diagnosis, and resolution of problems. Begins with the identification of a problem and does not end until services have been restored and the problem no longer adversely affects users with a minimal interruption of service.
The seven step of the network + troubleshooting model
- Identify the problem
- Establish a theory of probable cause
- Test the theory to determine cause
- Establish a plan of action to resolve the problem and identify potential effects
- Implement the solution or escalate as necessary
- Verify full system functionally and implement preventative measure is applicable
- Document findings, actions and outcomes
List some things you include in a troubleshooting documentation template
A description of the initial trouble
A description of the conditions surrounding the problem
Whether or not you could reproduce the problem consistently
The exact issue you identified
The possible causes you isolated
The corrections you formulated
The results of implementing each correction you tried
The results of testing the solution
Any external sources used.
Troubleshooting with IP configuration utilities in TCP/IP network
a common first step is to verify the hosts IP addressing Information is correct.
Use ipconfig or ifconfig with Unix to determine if the host is configured for static or dynamic IP addressing and if it has a valid IP address
Use the utility to release and renew the address
Use The ping utility as an initial step in diagnosing general connectivity problems. These steps include
Ping the Loopback address 127.0.0.1 to test whether TCP/IP has initialized on an individual system
Ping a specific system to verify that it is running and is connected to the networking
Ping by IP address instead not host name to determine if it is a problem related to name resolution.
Localize the problem: ping the local Loopback address. Ping the systems own IP address. Ping the address of the default gateway. Ping the address of a remote host
When you ping a computer, it will respond with one of the following responses.
Normal response. The computer responds normally with requested data for different parameters
Destination unreachable. Target computer was identified but was not reachable by the default gateway
Unknown host. The target compute is unknown and unreachable
Destination does not respond. No response to the ping
Network or host unreachable. The routing table does not contain any entry for the network or the host.
Tracert utility
Use to determine where the communication fail of you cannot connect to a remote host
Issue this command from the local machine to see how far the trace gets before you receive an error message. Using the IP address of the last successful connection you know where to begin troubleshooting
Use traceroute command in Unix
The arp utility
Supports the ARP service of the TCP/IP protocol suite. It enables an administrator to view the ARP cache and add or delete cache entries. It is also used to locate a nodes hardware address. Any added entry becomes permanent until it is deleted or the machine is shut down
Can be used to help troubleshoot duplicate IP address problems and to diagnose why a workstation cannot connect to a specific host.
The arp -a command will return a tabular listing of all ARP entries in the nodes ARP cache
The arp options
Arp inet_addr used with other options to specify an Internet address
Arp eth_addr used with other options to specify a physical address
Arp if_addr used with other options to specify the Internet address of the interface whose arp table should be modified
Arp -a displays the current arp entries in the cache
Arp -a inet_addr specify a particular IP address
Arp -g displays the same info as -a option
Arp -N if_addr displays the ARP entries for the network interface specified by if_addr
Arp -d deletes a single host entry of followed by if_addr. Deletes all host entries if followed by *
Arp -s inet_addr eth_addr add a host
Arp used in conjunction with ping
Used to troubleshoot ore complex network problems.
Ping a host on the network and if no reply may be firewalls preventing the ping from returning accurate info
Use the arp command to find the host by the MAC address and bypass the IP address resolution.
The ARP cache is a table used
For maintaining the correlation between MAC address and its corresponding IP address. Is a finite size. Periodically flushed to free up memory
The NBTSTAT Utility
A window utility used to view and manage NETBIOS over TCP/IP status information.
Displays NetBIOS name tables for both the local computer and remote computers and also the name cache. The name tables enable you to verify the connection establishment.
The NBTSTAT options
NBTSTAT -a [remote name] displays the NetBIOS name table of the remote computer specified by the name
NBTSTAT -A [IP address] displays the NetBIOS name table of the remote computer specified by the IP address
NBTSTAT -c displays the NetBIOS name cache of the local computer
NBTSTAT -n lists the local NetBIOS name table along with the service code, type, and status
NBTSTAT -r lists NetBIOS names resolved by broadcast and via WINS
NBTSTAT -R purges the cache and reloads static entries from the LMHOSTS file
NBTSTAT -S lists NetBIOS connections and their state with destination IP addresses
NBTSTAT -s lists NetBIOS connections sun their stare converting destination IP addresses to computer NetBIOS names
NBTSTAT -RR sends name release packets to the WINS server and then starts refresh
The NETSTAT Utility
Shows the status of each active network connection
Will display statistics for both TCP and UDP
Because UDP is connectionless no connection information will be shown for UDP packets.
The several functions of the NETSTAT troubleshooting tool
Use to find out if TCP/IP based programs (SMTP or FTP) is listening on the expected port. If not the system needs to be restarted
Check the statistics to see if the connection is good.
Use statistics to check network adapter error counts
Used to display routing tables and check for network routing problems.
NETSTAT Command options
NETSTAT -a all connections and listening ports
NETSTAT -e ethernet statistics
NETSTAT -n addresses and port numbers in numerical form
NETSTAT -o process ID associated with each connection
NETSTAT -p [protocol] connections for the protocol specified. Value of protocol may be TCP, UDP, TCPv6 or UDPv6
NETSTAT -r routing table
NETSTAT -s statistics grouped by protocol - IP, IPv6, ICMP, ICMPv6, TCP, TCPv6, UDP, UDPv6
NETSTAT [interval] refreshes statistics specified in the command. CTRL+C stops refreshing
NETSTAT will display several socket states
SYN_SEND connection is active and open
SYN_RECEIVED server received the synchronize flag set from the client
ESTABLISHED client received the servers SYN and the session is established
LISTEN server is ready to accept a connection
FIN_WAIT_1 connection is active but closed.
TIMED_WAIT client enters this state after FIN_WAIT_1
CLOSE_WAIT passive close. Server received FIN_WAIT_1
FIN_WAIT_2 client received an ack of its FIN_WAIT_1 for the server
LAST _ACK server in this state when it sends its own FIN
CLOSED server received an ACK from the client and the connection is closed
The Nslookup utility
Used to test and troubleshoot domain name servers
Has two modes: the interactive mode. Enable query names servers for info about hosts and domain or to print a list of hosts in a domain
The non-interactive mode. Prints only the name and requested details for one host or domain.
nslookup syntax
For interactive mode: nslookup
Or. Nslookup [- option] [computer to find | - [dns server ]
Non interactive mode. Nslookup [name or IP addres of computer to look up] [ name or IP address of DNS]
System and Network Integrates Polling Software SNIPS Is
A system and network monitoring software tool that runs on Unix systems.
Offers both command line and web interfaces to monitor network and system devices. The monitoring functions determine and report the status of services running in the network.
What tools should be included in a network technicians toolbox
Variety of screwdrivers and spare screws Long nose pliers Small diagonal cutting pliers Small adjustable wrench Variety of wrenches or nut drivers Small AA or AAA flashlight Anti static wrist strap with clip
What are wide crimpers
A tool that attaches media connectors to the ends of cables. Use it if you need to make your own network cables or trim the end of a cable.
Usually comes with a cable stripper allowing the user to strip wires of their protective coating and use the crimping tool to attach a media connector
What is a pinch down block
Used to connect one group of telephone and network wires with another group in utility or telecommunication closets. Typically support low bandwidth Ethernet and Token Ring networks
Name the two primary types of punch down
Blocks
66 block. Used in the telephone industry to terminate telecommunications. Supports low bandwidth telecommunications transmissions.
110 block. Punch down block or cable termination block used for structured wiring systems. Multi pair station cables are terminated, allowing cross connection to other punch down locations. Supports higher bandwidth and suitable for use in data applications
What are punch down tools
Used in a wiring closet to connect cable wires directly to a patch panel. Strips the insulation from the end of the wire and embeds the wire into the connection at the back of the panel.
What is a circuit tester
An electrical instrument used for testing whether or not current is passing through the circuit.
What is a multimeter
An electronic measuring instrument that takes electrical measurements such as voltage, current, and resistance. Can be analog or digital.
Four categories
I low current levels
II interior residential
III distribution panels, motors, and appliance outlets
IV high current applications
What is a voltmeter
Measures voltage and resistance between two points in a circuit. Come in analog and digital.
Digital volt meter DVM provides scales for reading voltages in AC and DC and different resistances.
Can be used to test resistances between cable endpoints or voltages inside a low power system. Not for high power equipment
What is a voltage event recorder
VER Used in conjunction with a voltmeter to test and verify the electrical signals transmitting through the network cables are within the requires specifications. Help diagnose electrical faults or Intermittent problems regarding low or high voltage
What is a cable tester
Or media tester
Is an electrical instrument that verifies if a signal is transmitted by a cable. Will determine whether a cable has an end to end connection and can detect shorts or opens but cannot certify the cable for transmission quality
What is a cable certifiers
A type of certifier that allows you to perform tests. Can detect shorts, crosstalk on a cables test the cable those and whether a cable is straight through or crossover and check if the NIC is functioning and at what speed: half or duplex.
What are crossover cables
A special network cable used in Ethernet UTP installations which enable devices to be connected without using a hub or switch. The transmit and receive lines are crossed to make them work like a Loopback, a function that the switch does.
In troubleshooting, crossover cables connects two stations’ network adapters directly without a switch so communications can be tested between them.
A T1 crossover cable is used to
Connect two T1 CSU/DSU devices by using T568B pairs
What is a straight though cable
A RJ 45 cable used for network connectivity
Crossover cable vs straight cable wiring
In regular Ethernet UTP patch cable Pins 1 and 2 transmit and Pins 3 and 6 receive.
In straight wired pin 1 is wired to pin 1 etc
In cross over pin 1 and 2 connect to pin 3 and 6 and vv
What is a hardware Loopback plug
a special connector used for diagnosing transmission problems. It plugs into a port and crosses over the transmit and receive lines. Commonly used to test ethernet NICs
The plug directly connects Pin 1 to Pin 3 and Pin 2 to Pin 6
For T1 testing connects Pin 1 to Pin 4 and Pin 2 to Pin 5
What are time domain reflectometers
TDR a measuring tool that transmits an electrical pulse on a cable and measures the reflected signal. Bends, short circuits, and connector problems on the cable modify a signals amplitude before it returns to a TDR. It analyzes the returned signal and based in the signals condition and its rate of return it checks the time span and determines cable problems. If attached on a coaxial cable network of will indicate whether terminators are installed properly and are functioning correctly
What is a tone generator
A device that sends an electrical signal through one pair of UTP wires. Can verify continuity and detect faults in UTP cables. Most commonly used on telephone systems to trace wire pairs.
What is a tone locator
Or toner probe
Is a device that emits an audible tone when it detects a signal in a pair of wires. Can verify continuity and detect faults in UTP cables. Most commonly used on telephone systems to trace wire pairs.
What is a butt set
Aka linemans test set
A special type of telephone handset used by telecom technicians when installing and testing local lines. Allows to bridge onto wire pairs with clips in order to monitor the line and use dialing features as if it were a physical phone on the system. Some can detect polarity reversals and other line faults to troubleshoot performance issues.
What are the different types of LED indicators on network adapters, switches, routers, and cable and DSL modems
Link indicators. Indicates signal reception from the network. If not lit it could indicate a problem with the cable or the physical connection
Activity indicators. Flickers when data packets are received or sent. Of constantly flickering the network might be overused or there is system generating noise
Speed indicators. Dual mode adapters have a speed indicator to display the adapter is operating at 10 Mbps, 100 Mbps, or 1 Gbps.
Dual color indicators. Indicate different network states. Green normal activity, Amber collisions in the network
What is a network analyzer
Aka packet or protocol analyzer or packet sniffer
A software or hardware tool that integrates diagnostic and reporting capabilities to provide a comprehensive view or an organizations network.
As data crosses a network an analyzer will intercept it, log It, and analyze the information according to baseline specifications.
What is a network sniffer
Can identify and capture data packets on a network, record and analyze traffic, and identify open ports on the network. Can analyze data packets from different protocols and identify data vulnerabilities on the network.
What is a demarc
A demarcation point where a buildings wiring ends and the telephone company’s wiring begins.
Can be installed on the outside of building. Common with residential Demarcs
Can be installed on the inside of a building common with most commercial and industrial Demarcs
What is a smart jack
A device that serves as the demarc between the end users inside wiring and local access carriers’ facilities
What is a wireless tester
A wifi spectrum analyzer used to detect devices and points of interference as well as analyze and troubleshoot network issues on a WLAN or other wireless networks. Gives an overview of health of a WLAN in once central location.
What is a spectrum analyzer
An instrument that displays the variation of signal strength against the frequency
What is WLAN survey software
Used to plan, simulate, and implement WLANs. Used before and after implementation to determine the health of the network based on defined measurable criteria.
Describe cause and resolution of the physical troubleshooting issue of cross talk where there is slow network performance and an excess of dropped or unintelligible packets. Users hear garbled voice or conversations from another line
Causes: occurs when two cables run in parallel and the signal of one cable interferes with the other. Also be caused by crossed or crushed wire pairs in Twisted pair cabling
Resolution: the use of twisted pair cabling or digital signals can reduce the effects. Maintaining proper distance between cables can help
Describe cause and resolution of the physical troubleshooting issue of near-end cross-talk where there is signal loss or interference
Causes: occurs along the transmitting end of the cable. Often occurs in or near the terminating connector
Resolution: test with cable testers from both ends and correct any crossed or crushed wires. Verify that the cable is terminated properly and that the twists in the pair of wires is maintained.
Describe cause and resolution of the physical troubleshooting issue of attenuation where there is slow responses from the network
Cause: degradation of signal strength
Resolution: in wired networks use shorter cable runs. In wireless networks add more access points and signal boosters along the transmission path.
Longer cable length, poor connections, bad insulation, a high level of cross-talk or EMI can all increase this issue. Evaluate the environment for interference.
Describe cause and resolution of the physical troubleshooting issue of collisions where there is high latency, reduced network performance, and intermittent connectivity issues.
Causes: tend to occur on networks as nodes attempt to access shared resources.
Resolution: depends. If network uses hubs replacing them with a switch will alleviate the problem
Describe cause and resolution of the physical troubleshooting issue of shorts where there are electrical snorts - complete loss of signal
Causes: two nodes of an electrical circuit that are meant to be at different voltages create a low resistance connection causing this issue
Resolution: use a TDR, time-domain reflectometers, to detect and locate shorts. Replace cables and connectors.
Describe cause and resolution of the physical troubleshooting issue of open impedance mismatch also known as echo where the tell tale sign of open impedance mismatch is an echo on either the talker or listener end of the connection
Causes: the mismatching of electrical resistance
Resolution: use a TDR to detect impedance. Collect and review data, interpret the symptoms, and determine the root cause in order to correct the cause
Describe cause and resolution of the physical troubleshooting issue of EMI interference where there is humming, cracking, and static are all signs of interference
Causes: can be caused by a number of devices
Resolution: remove or avoid environmental interferences as much as possible. Turning off competing devices or relocating them. Ensure there is adequate LAN coverage.
Describe cause and resolution of the physical troubleshooting issue of bad modules SFPs or GBICs where there is no communication through the devices
Causes: modules get corrupted
Resolution: replace the faulty devices
Describe cause and resolution of the physical troubleshooting issue of cable problems where the nodes on the network cannot communicate. The router, switches, and the individual nodes on the network are full functional but the problem persists
Causes: there is a problem with the network cables
resolution: bad connectors- check and replace the faulty connectors, verify that the cables are secured to the connectors and are properly crimped
Bad wiring- check and replace the wires that are in bad condition
Open, short cables- use cable testers and locate open or short cables, repair the cables and recheck that the issues are resolved. If not replace the cables
Split cables- identify the split cables and replace them with compatible cables
DB loss- check the cable for defects or Damage, crimping, and connection with the connectors. Identify and remove sources of interference
TXRX reversed- check the network port indicators on the system, if the link light is off there is an issue with the network adapter. Replace the network adapter
Cable placement- verify that the cable is placed away from source of EMI. Identify and remove the sources of interference.
Distance- verify that the cable are run inky for the max distance they are supported.
Describe cause and resolution of the logical troubleshooting issue port speed where there is no or low speed connectivity between devices
Causes: ports are configured to operate at different speeds and are therefore incompatible with each other
Resolution: verify that equipment is compatible and is operating at compatible speeds.
Describe cause and resolution of the logical troubleshooting issue of port duplex mismatch where there is late collisions, port alignment errors, and FCS errors are present during testing
Causes: caused by configuration errors. Occur when the switch port and a device are configured to use a different set of duplex settings, or when both ends are set to auto negotiate the settings
Resolution: verify the the switch port and the device are configured to use the same duplex setting. May need to upgrade devices
Describe cause and resolution of the logical troubleshooting issue of wrong VLAN where there is no connectivity between devices
Causes: devices are configured to use different VLANs
Resolution: reconfigure the devices to use the same VLANs
Describe cause and resolution of the logical troubleshooting issue of wrong IP address where there is no connectivity between devices
Causes: either the source or destination device had an incorrect IP address
Resolution: use the ping command to determine if there is connectivity between devices.
If a network is running a rogue DHCP server, two computers could have been leased the same IP address. Check TCP/IP configuration into using ipconfig /all on windows and ifconfig on Linux/Unix/MAC machines. Confirm the issue, troubleshoot DHCP. Could be that a static IP address was entered incorrectly. Check IP addresses and empty the ARPS cache on both computers
Describe cause and resolution of the logical troubleshooting issue wrong gateway address where there is no connectivity between devices
Causes: the IP address of the gateway is incorrect for the specified route
Resolution: change the IP address mod the gateway to the correct address
Describe cause and resolution of the logical troubleshooting issue of wrong DNS Where there is no connectivity between devices
Causes: a device is configured to use the wrong DNS server
Resolution: open TCP/IP properties and check the IP address of the DNS server listed for the client. Replace with the correct IP address and test connectivity
Describe cause and resolution of the logical troubleshooting issue of wrong subnet mask where there is no connectivity between devices
Causes: either the source or destination device has an incorrect subnet mask
Resolution: use the ping command to determine of there is connectivity between devices. Check the subnet mask on no devices. Change the incorrect subnet mask to a correct one and test connectivity
Describe cause and resolution of the logical troubleshooting issue of duplicate IP address where the system displays notification that the same IP address is in use on the network. No connectivity between devices
Causes: the same IP address is assigned to more than one system
Resolution: if network is DHCP enabled, try to identify the systems that are assigned IP addresses manually and change the IP address of such systems to be outside the DHCP scope. If network not DHCP Enabled, locate the system that have the same IP address, and change the IP address in one of the systems.
Describe cause and resolution of the logical troubleshooting issue of power failure where there is a power failure that affects switches and routers
Causes: switch and router adapters connect to cable modems which depend on the availability of power.
Resolution: use cable modems and other network devices with battery backed power supplies to ensure that there is uninterrupted service of several hours in case of local power failures.
Describe cause and resolution of the logical troubleshooting issue of bad/missing routes where the router is sending packets using an invalid path
Causes: the router setting is incorrect
Resolution: check and change the router setting and reboot the router for the changes to be effected.
Describe the cause and resolution for troubleshooting the wireless issue of interference where there is low throughout, network degradation, dropped packets, intermittent connectivity, and poor voice quality.
Causes: can be caused by a number of devices including cordless phones, Bluetooth devices, cameras, paging systems, unauthorized access points, metal building framing, and clients in ad-NIC mode.
Resolution: remove or avoid environmental interferences.
Describe the cause and resolution for troubleshooting the wireless issue of incorrect encryption type where the encryption types between two devices do not match, no connection is established or if different encryption keys are used between two devices, they cannot negotiate key information for verification and decryption in order to initiate communication
Causes: improper configuration and different encryption types
Resolution: ensure that the security settings match between and among devices
Describe the cause and resolution for troubleshooting the wireless issue of Congested channel where there is very slow speeds
Causes: interference from neighboring wireless networks ; congested network channels
Resolution: log into the router and manually change th channel the wireless router is operating on
Describe the cause and resolution for troubleshooting the wireless issue of incorrect frequency where there is no connectivity
Causes: devices must operate on the same frequency
Resolution: deploy devices that operate on the same frequency
Describe the cause and resolution for troubleshooting the wireless issue of SSID mismatch where there is no connectivity
Causes: devices are configured to use different ESSIDs
Resolution: set the devices to use the same SSID ensure that the wireless client and the access point are the same.
Describe the cause and resolution for troubleshooting the wireless issue of standard mismatch where there is no connectivity between devices
Causes: devices are configured to use different standards such as 802.11a/b/g/n.
Resolution: devices chosen to work together should use the same standard to operate
Describe the cause and resolution for troubleshooting the wireless issue of signal strength where there is low signal strength and throughput
Causes: the distance between two points causes this connectivity issue. The longer the distance between the two devices, the lower the signal strength. Issues that can occur because of low signal strength include latency, packet loss, re transmissions, or transient traffic.
Resolution: add another point to increase coverage, use a spectrum analyzer to determine coverage and signal strength.
Describe the cause and resolution for troubleshooting the wireless issue of bounce where there is no or low connectivity between devices
Causes: signals from device bounces off obstructions and are not received by the receiving device
Resolution: move one of the devices to avoid obstructions. Monitor performance and check for interference.
Describe the cause and resolution for troubleshooting the wireless issue of antenna placement where there is no or low connectivity
Causes: the position of your antenna can negatively affect overall performance of placed incorrectly
Resolution: alter the position of the antenna and Monitor device performance.
Describe the cause and resolution for troubleshooting the wireless issue of configurations where the wireless modem is active, but clients cannot access the Internet.
Causes: configuration of the wireless modem os incorrect
Resolution: check the configuration of the wireless modem by assessing the web admin interface
Check the encryption type, SSID, and pass phrase text that is specified and confirm that the wireless modem was rebooted after the configuration change.
Ensure that the clients can also support the same encryption type
Verify that the same SSID and key phrase are defined in the network connection
Verify that the wireless receiver on the desktop is configured properly with the correct compatibility drivers installed
For a laptop check that the wireless network adapter is functional and turned on. Update device driver on the client systems
What is the typical IP address for accessing the admin interface for some routers
Http://192.168.1.1
Describe the cause and resolution for troubleshooting the wireless issue of incompatibilities where the wireless device is not accessible from the client
Causes: the settings on the wireless device is not compatible with the clients
Resolution: check the configuration of the wireless modem by accessing the web admin interface. Verify that the client systems can support the same configuration. If not, identify the configuration supported on both the clients and the servers and apply the same on the wireless device and the client systems
Describe the cause and resolution for troubleshooting the wireless issue of incorrect channel where the wireless signal is not accessible even within the expected range
Causes: most common could be another wireless device or application that operates at the same frequency level creating conflict
Resolution: identify the conflicting device and move it to another location outside the reach of the WAPS. If it is not possible to relocate the device, change the channel of one of the devices such that they operate on a difference frequency. Ensure that the cordless phones, microwaves, and other electrical equipment are at a safe distance from the access point
Describe the cause and resolution for troubleshooting the wireless issue of latency where the delay in Data transmission on the network is very high
Causes: the signal strength is weak or the position of the wireless antenna is modified
Resolution: verify that the wireless modem is functional. Change the antenna to the position that gives the best performance
Describe the cause and resolution for troubleshooting the wireless issue of incorrect switch placement where the switch performance is considerably reduced
Causes: there is a conflicting device in the range which is causing the interference that results in the switch performance being degraded
Resolution: locate the conflicting device, move it to another location. If not possible rework the network layout and determine a better position for the switch such that there is no conflict with other devices. Monitor the switch performance periodically to prevent further occurrence of the issue
Describe the causes and resolution for the troubleshooting issue of switching loop where there is a switching loop on the network
Causes: packets are switched in a loop
Resolution: needs STP Shielded Twisted Pair to ensure loop free switching of data. Rework on the network arrangement and cabling to prevent the switching loop
Describe the causes and resolution for the troubleshooting issue of routing loop where there is a routing loop on the network
Causes: Packets routed in a loop
Resolution: recheck the router configuration and adjust it to prevent a routing loop
Describe the causes and resolution for the troubleshooting issue of route problems where the packets do not reach their intended destination
Causes: this could be caused by configuration problems, route convergence, broken segments, or router malfunctioning
Resolution: verify that the router is functional. I’d necessary replace the router
Describe the causes and resolution for the troubleshooting issue of proxy arp where the proxy server is not functional
Causes: the proxy settings are misconfigured. This may lead to DoS attacks
Resolution: correct the proxy setting to resolve the issue
Describe the causes and resolution for the troubleshooting issue of broadcast storms where the network becomes overwhelmed by constant broadcast traffic generated by a device on the network
Causes: there are too many broadcast messages being sent in parallel, causing him network traffic
Resolution: identify the device and reconfigure it to increase the interval of broadcast messages. On the network, apply restrictive setting to prevent network nodes from sending broadcast messages
Describe the causes and resolution for the troubleshooting issue of port configuration where it is incorrect
Causes: the recent changes made to the port configuration were incorrect
Resolution: on the system console of the switch, verify the port properties of the individual nodes and check their status. If required restore the port configuration to its default setting from the last backup
Describe the causes and resolution for the troubleshooting issue of VLAN assignment where the nodes in the network cannot communications are with one another
Causes: by default computers on different segments are added to different VLANs and they cannot communicate with one another unless the switch is configured to allow communication between computers on different VLANs
Resolution: check the VLANS assignment on the switch console and reassign the computers to the VLAN to enable communication among the. Ensure that the IOS of the switch is updated to reflect the latest settings
Describe the causes and resolution for the troubleshooting issue of mismatched MTU/MTU black hole where the Maximum transmission unit, MTU, is inaccessible
Causes: the TCP/IP connection handshake does not occur between the devices (routers) and the connection cannot be established
Resolution: reconfigure the MTU to check whether the problem gets resolved. If not replace the device
In the command prompt use this command to see network details
Ipconfig /all | more
In the command prompt if you ping DC what will result
The DNSs servers IP address
Use this command in the command prompt to view your NetBIOS name cache
NBTSTAT -c -n
