Exam Tip in Software

Encoder QR Code ISO/IEC18004 in Software Exam Tip

TCP/IP utilities need to be run from a command prompt with administrative privileges To do so, right-click the Start Menu command prompt icon and choose Run as Administrator from the context menu

Shows information about your IP connection, including any DNS and WINS servers used, whether the address is dynamic or static, and the host name Releases the IP address that has been assigned through DHCP You cannot release a leased IP address through the TCP/IP Properties dialog box Renews a DHCP address Not possible through the TCP/IP Properties dialog box Reregisters the DNS name with the configured DNS server Can be useful for troubleshooting name resolution problems Clears the contents of the DNS resolver cache located on the workstation A client will check its DNS resolver cache before checking a DNS server This will clear out an incorrect entry made by an improperly configured DNS server

Once you have a valid IP address, the next step is usually to test connectivity to another computer The Packet Internet Groper (PING) utility is used to do just that PING works by sending a packet of information that behaves much like sonar does for submarines If a PING is successful, the receiving computer responds, and you ve confirmed that both systems can send and receive TCP/IP packets Thus, other communication should work as well Typical PING syntax goes like this:

If you re not able to PING using the IP address, for example, something s amiss in the network in between source and destination (assuming the target computer is on) If you can PING using the IP address and not the computer name, the problem lies with name resolution Further, PING can be used with a series of modifiers that change the default behavior of sending four 32-byte packets out to the designated host for response Some of these can change the size of the PING packet, others can modify the duration of the ping test Again, use the / (help) switch to see a list of these modifiers

Firewalls can (and often are) also set to deny or drop PING requests, as PING attacks are an unsophisticated way to tamper with a server by tying up its resources responding to PING requests For example, you won t be able to ping wwwmicrosoftcom even though it can be reached PING is best used to troubleshoot in a private, corporate environment

When communication is failing, the general flow to PING to verify TCP/IP connectivity from a computer is as follows:

PING the loopback address of 127001 PING the local computer s IP address PING the default gateway PING the remote computer you are trying to reach using first the IP address (if known) and then the computer name

How does a packet of information get from point A to point B The TRACERT utility addresses this very question It works by employing PING packets, albeit with slight modifications If you test a connection using a normal PING packet, each packet has a time-to-live (TTL) value of 128, meaning that it can stop at up to 127 different routing points along its way (When the TTL value reaches 0, the packet is dropped Without this characteristic, all undelivered traffic on the Internet would still be out there, passing from one router to the Net in a never-ending attempt to find a destination) The TRACERT utility uses this same PING packet, but it has an initial TTL value of 1, meaning that the packet will die at its first stop When it dies, TRACERT notes the IP address of the device that dropped the packet The next PING packet sent to the destination has a TTL value of 2 This packet dies two hops away from its source, and TRACERT logs where it dies And so on and so on, until the PING reaches its destination, at which time the route from source to destination has been reconstructed Because it steps through the complete path taken by information, it can be very helpful in identifying slow or broken links in the information chain The syntax is very similar to PING: