TCP IP INTERVIEW QUESTIONS

1. What are the components which constitute a TCP/IP socket pair.

A socket pair comprises of source port, destination port, destination IP address and source IP address.

2. How is the source port number in a transport layer header derived

The source port number is derived by the operating system and is unique for every connection.

3. What is the source port number in a TCP packet which is targeted to a Web server.

The source port number would be a random number which is derived by the operating system.

4. Name 3 common fields which is found in TCP and UDP headers

The source port, destination port and checksum are common fields which are part of TCP and UDP headers




5. Which tool can be used to find the list of TCP/IP connections on an operating system.

netstat command is used for identifying the list of TCP/UDP connections on a operating system.

6. Which ports numbers are used initially by a FTP client to establish connectivity with a FTP server.

FTP servers work on TCP port 20 and 21. FTP clients initially establish 3 way handshake connectivity with TCP port 21, which is the control connection. After successful connection, another 3 way handshake is established with TCP port 20 , which is the FTP data port.

7. What is configured on the TCP/IP adapter of a PC for deriving the network address in the routing table.

The network address is derived by Anding operation with the IP address and subnet mask which is configured on the TCP/IP adapter of a PC.

8. What happens when the command ping tcpipguru.com is typed on command prompt.

When a ping is initiated to a website name, a DNS resolution follows which would retrieve the IP address on which the website is hosted. The system would now initiate the ping to the servers IP address (Web server on which tcpipguru.com is hosted), which is received after DNS resolution, following which the servers IP address responds.

9. Which protocol do https servers use at the transport layer.

https servers use TCP at the transport layer. TCP port 443 is used.

10. A user on a PC behind a NAT router access tcpipguru.com. To which IP address would the DNS query packet be sent to from the PC for name resolution.

DNS queries from the PC would be sent to the DNS server IP address which is configured on the PC.


11. Does HTTP commence data transfer before or after the TCP 3 way handshake.

Data transfer commences after TCP 3 way handshake.

12. Name a layer 2 protocol which does not use TCP.

ARP protocol does not use TCP.

13. Which transport layer protocol does ping use

Ping does not use any transport layer headers. It uses ICMP at the network layer.

14. Which protocol does ping and tracert use in common

Ping and tracert uses ICMP at the network layer.

15. Which VPN protocol uses TCP port 1723 for communication

PPTP uses TCP port 1723 for communication.

16. Which field in an IP header does a router look to forward the packet.

Routers look into the destination IP address in the IP header to forward the packet.