The Telnet Command

Technically, telnet is a protocol. This means it is a language that computer use to communicate with one another in a particular way.  From your point of view, Telnet is a program that lets you login to a site on the Internet through your connection to Teleport. It is a terminal emulation program, meaning that when you connect to the remote site, your computer functions as a terminal for that computer.

Once the connection is made, you can use your computer to access information, run programs, edit files, and otherwise use whatever resources are available on the other computer. What is available depends on the computer you connect to. Most of the times, if you type '?' or 'help', you would normally receive some type of information, menu options, etc.

                     Note: telnet connections give you command-line access only. In other

                     words, instead of being able to use buttons and menus as you do with a

                     graphical interface, you have to type commands. However, telnet allows

                     you to use certain utilities and resources you cannot access with your

                     other Internet applications.

Usage:     telnet  hostname or IP address  port(optional)

The Netstat Command

This command is used to query the network subsystem regarding certain types of information. Different types of information will be received depending on the switches used in conjunction with this command.

The IpConfig Command

The ipconfig command will give you information about your current TCP/IP configuration. Information such as IP address, default gateway, subnet mask, etc can all be retrieved using this command.

The Finger Command

By default, finger will list the login name, full name, terminal name, and write status (shown as a "*" before the terminal name if write permission is denied), idle time, login time, office location, and phone number (if known) for each current user connected to the network.

Usage:    finger  username@domain

Switches:     -b    Brief output format

                   -f     Supresses the printing of the header line.

                       -i     Provides a quick list of users with idle time.

                       -l     Forces long output format.

                       -p    Supresses printing of the .plan file (if present)

                       -q    Provides a quick list of users.

                       -s    Forces short output form.

                       -w   Forces narrow output form.

The Arp Command

The arp command will display internet to ethernet (IP to MAC) address translations which is normally handled by the arp protocol. When the hostname is the only parameter, this command will display the currect ARP entry for that hostname.

Usage:   arp hostname

Switches:     -a            Displays current ARP entries by interrogating the current

                                          protocol data.  If inet_addr is specified, the IP and Physical

                                          addresses for only the specified computer are displayed.  If

                                          more than one network interface uses ARP, entries for each ARP

                                          table are displayed.

                  -g            Same as -a.

                  inet_addr     Specifies an internet address.

                  -N if_addr    Displays the ARP entries for the network interface specified

                                                by if_addr.

                  -d               Deletes the host specified by inet_addr.

                  -s            Adds the host and associates the Internet address inet_addr

                                         with the Physical address eth_addr.  The Physical address is

                                          given as 6 hexadecimal bytes separated by hyphens. The entry

                                         is permanent.

                  eth_addr      Specifies a physical address.

                  if_addr       If present, this specifies the Internet address of the

                                              interface whose address translation table should be modified.

                                              If not present, the first applicable interface will be used.

The Nbtstat Command

Can be used to query the network concerning NetBIOS information. It can also be useful for purging the NetBIOS cache and reloading the LMHOSTS file. This one command can be extremely useful when performing security audits. When one knows how to interpret the information, it can reveal more than one might think.

The Ping Command

The ping (Packet Internet Groper) is used to send ICMP (Internet Control Message Protocol) packets from one host to another. Ping transmits packets using the ICMP ECHO_REQUEST command and expects an ICMP ECHO_REPLY.

Usage:    ping IP address or Hostname

Switches:    -t             Ping the specifed host until interrupted.

                     -a             Resolve addresses to hostnames.

                     -n count       Number of echo requests to send.

                     -l size        Send buffer size.

                     -f             Set Don't Fragment flag in packet.

                     -i TTL         Time To Live.

                 -v TOS         Type Of Service.

                 -r count       Record route for count hops.

                 -s count       Timestamp for count hops.

                 -j host-list   Loose source route along host-list.

                 -k host-list   Strict source route along host-list.

                 -w timeout     Timeout in milliseconds to wait for each reply.

The Traceroute Command

The traceroute command is used to trace the route that a packet takes to reach its destination. This command works by using the time to live (TTL) filed in the IP packet.