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Troubleshooting Networks (Network Issues (MTU Maximum Transmission Unit …

- - - - Remote
        Question Users
        Close-ended ?s for experienced users
        Open-ended ?s for novice users
      - On site
        Identify Symptoms first hand
      - Duplicate Problem
        Log into users comp
        Log in under different user
  - - - Top-to-bottom OSI Model Approach
      - Divide and Conquer
        
        As you gather information for troubleshooting, a general sense of where the problem lies should manifest. Place this likely cause at the appropriate layer of the OSI model and begin to test the theory and related theories at that layer.
      - Bottom-to-top OSI Model Approach
  - - - Establish New Theory
        Return to step 2
      - Escalate the Problem
        
        Inform other parties for guidance
        
        Pass job off to another authority who has control over device/issue
- - - - Patch
        Flat plate shaped antennas
        Generates half sphere beam
        Always on walls
      - Unidirectional
        Directs signal in specific direction
      - Omnidirectional
        Radiates outward in all directions from WAP
- - - - Certifiers
        will report speed and duplex settings
  - - - Speed Test Sites
      - Protocol Analyzer
        Lets you look at protocols running at different levels of network
        helps you determine slowdowns on a network by giving you an idea of excess or unexpected traffic
      - Looking Glass Sites
        Runs diag from outside of the network
        ping, traceroute, etc
      - Wifi Analyzer
        documents all existing wireless networks in the area
        Handheld tool or software on laptop
    - - arp
        helps diagnose problems associated with the Address Resolution Protocol (ARP). CompTIA refers to the output of the arp command as the MAC address lookup table, while most folks would just call it the arp cache or arp table.
      - ping
        test the connection between two nodes
        Uses ICMP
        
        ping -6
        use IPv6
        
        ping –t
        tells ping to run indefinately
        
        Can test availability of Sites using FQDNs(Google.com)
        Use to test DNS
        
        Destination host unreachable
        This message means, “I can’t get to that IP address.” In this case, you should check for possible routing problems—for example, have you specified a default gateway?
        
        Unknown host
        This message means, “I don’t know the IP address!” You probably specified an invalid/unused DNS name.
      - pathping
        ombines the functions of ping and tracert and adds some additional functions.
      - tracert
        traces the route between two hosts
      - ipconfig and ifconfig
        
        ifconfig The ifconfig command displays or sets settings on a network card on a UNIX/Linux/OS X system.
        • ifconfig Displays the network card and IP settings
        • ifconfig eth0 up Enables the first Ethernet card
        • ifconfig eth0 down Disables the Ethernet card
        
        ipconfig The ipconfig command is used i*n Windows to display the IP address information of the system.
        • ipconfig /all Displays all TCP/IP settings and the MAC address
        • ipconfig /displaydns Displays the DNS resolver cache
        • ipconfig /flushdns Clears out the DNS resolver cache
      - nslookup
        provides a command-line utility for diagnosing DNS problems
      - netstat
        enables a network tech to examine network statistics about a system
        Listening ports or established connections
        
        -a
        ALL connections and listening ports
        
        -b
        exe involved in creating each connection of listening port
        
        -e
        ETHERNET Stats
        
        -f
        Fully Qualified Domain Names (FQDN) for foreign addresses
        
        -n
        Addresses and ports in NUMERICAL form
        
        -o
        OWNING process ID associated with each connection
        
        -p protocol
        Shows connections for protocol specified
        
        -r/route print
        ROUTING table
        
        -s
        Per-protocol Stats
        
        -t
        Current Connection offload State
        
        -interval
        Redisplays selected stats, pausing interval seconds between each display
      - nbtstat
        enables a network tech to check information about the NetBIOS name
        
        -a
        lists remote machine's name table given it's name
        
        -A
        lists temote machine's name table given its IP address
        
        -c
        lists NBT's cache of remote machine names and their IP addreses
        
        -n
        lists local NetBIOS names
        
        -R
        Purges and reloads the remote cache name table