a. TCP/IP is the medium of transport when your are accessing the Internet.
b. Some important TCP/IP port numbers are as given below:
1. FTP: 21, stands for File Transfer Protocol is a client server protocol Your Windows machine, running FTP client can communicate with the Unix Server running FTP server daemon, and transfer files to and from your computer.
2. Telnet: 23, stands for Telnetting from a remote terminal to a Telnet Server
3. SMTP: 25, stands for Simple Mail Transfer Protocol
4. https/WWW: 80, stands for Hyper Text Transfer Protocol
5. POP3: 110, stands for Post Office Protocol
6. https: 443, stands for https Secure
c. TCP/IP is the protocol used when you are Telnetting to a remote host. https is used for accessing the World Wide Web services.
d. Some of the important commands useful in trouble shooting TCP/IP networks are:
1. Ipconfig: Displays TCP/IP configuration values, including IP address, subnet mask, and default gateway. Available options with ipconfig command are given below:
i. /? Display this help message
ii. /all Display full configuration information.
iii. /release Release the IPv4 address for the specified adapter.
iv. /release6 Release the IPv6 address for the specified adapter.
v. /renew Renew the IPv4 address for the specified adapter.
vi. /renew6 Renew the IPv6 address for the specified adapter.
vii. /flushdns Purges the DNS Resolver cache.
viii. /registerdns Refreshes all DHCP leases and re-registers DNS names
ix. /displaydns Display the contents of the DNS Resolver Cache.
x. /showclassid Displays all the dhcp class IDs allowed for adapter.
xi. /setclassid Modifies the dhcp class id.
xii. /showclassid6 Displays all the IPv6 DHCP class IDs allowed for adapter
xiii. /setclassid6 Modifies the IPv6 DHCP class id.
2. nslookup provides the IP address of the remote computer after querying the dns server for the IP config information.
3. Ping: This command can be used to verify whether the target ip address or host name is present. You need to specify the target IP address or host name. You can ping the loop back address at 127.0.0.1. A response ensures that the TCP/IP stack is installed properly on your computer.
4. Route: Displays and manipulates route information.
5. Tracert: Determines the route packets take to reach the specified destination.
e. To see TCP/IP configuration on a Windows 95 / 98 computer, use WINIPCFG. It will display your IP address, subnet mask, default gateway, hardware MAC address.
f. To see TCP/IP configuration on an NT machine, use IPCONFIG. It will also display the IP configuration information on an NT machine. To get more details, use IPCONFIG/ALL.
g. To verify that client computer is configured properly with appropriate IP address, subnet mask , and default gateway use Ipconfig/all command.
h. If indicator light on network switch is blinking rapidly even when all other computer nodes are disconnected it is very likely that the switch port or the switch is bad.
2. SMTP is used to upload mail to the mail server. POP3 is used for downloading mail from a mail server to a client machine running POP3 client.
3. Both PPP and SLIP can be used for dial up connections. However, SLIP can't be used where the IP address need to be assigned dynamically. The advantage of PPP is multi protocol support, that it can support TCP/IP, IPX, AppleTalk etc. SLIP can support only TCP/IP and IP addresses need to be assigned manually.
4. WINS server resolves the NetBIOS names to IP addresses. A Windows network running TCP/IP need to be configured with WINS (or LMHOSTS file on each computer) for NetBIOS name resolution.
5. HOSTS file and DNS (Domain Name Server) are used for resolving FQDNs (Fully Qualified Domain Names) to IP addresses.
6. Networking utilities
a. NBTSTAT: This utility displays current NetBIOS over TCP/IP connections, and display NetBIOS name cache.
b. NETSTAT: Displays protocol statistics and current TCP/IP connections since the server was last booted.
c. TRACERT: Used to determine which route a packet takes to reach its destination from source.
d. IPCONFIG: Used to display Windows IP configuration information.
e. NSLOOKUP: This utility enables users to interact with a DNS server and display resource records.
f. ROUTE: Used to display and edit static routing tables.
g. Netsh is a command-line scripting utility that allows us to, either locally or remotely, display or modify the network configuration of a computer. Netsh also provides a scripting feature that allows us to run a group of commands in batch mode against a specified computer.
7. A user can start a DHCP client service by going to Control Panel or using My Computer as below:
control Panel -> Administrative Tools -> Services -> DHCP client Services -> Start
My Computer -> Manage -> Services and Applications -> Services -> DHCP client Services -> Start
8. APIPA stands for Automatic Private IP Addressing. A feature of Microsoft Windows, APIPA is a DHCP failover mechanism. With APIPA, DHCP clients can obtain IP addresses when DHCP servers are nonfunctional. APIPA exists in all popular versions of Windows except Windows NT.
When a DHCP server fails, APIPA allocates IP addresses in the private range 169.254.0.1 to 169.254.255.254. C