interview question and answer - set 2

Question No 11. What is the port number of FTP, SSH, TFTP, Telnet, SMTP, POP3, SNMP?

FTP Data -20 - File Transfer Protocol

FTP control – 21 – File Transfer Protocol

SSH – 22 - Secure Shell

TFTP – 69 – Trivial File Transfer Protocol
TELNET – 23 – Remote access

SMTP – 25 – Simple Mail Transfer Protocol

POP3 – 110 – Post Office Protocol

SNMP – 161 – Simple Network Management protocol

Question No 12. Who will release the Public ip address pool to the ISP (Internet Service Provider)?

IANA – Internet Assigned Number Authority.

IANA is responsible for global coordination of the Internet Protocol addressing systems, as well as the Autonomous System Numbers used for routing Internet traffic.

Two types : IP version 4 (IPv4) and IP version 6 (IPv6). IPv4 was initially deployed on 1 January 1983 and is still the most commonly used version. IPv4 addresses are 32-bit numbers often expressed as 4 octets in “dotted decimal” notation. Deployment of the IPv6 protocol began in 1999. IPv6 addresses are 128-bit numbers and are conventionally expressed using hexadecimal strings.

Users are assigned IP addresses by Internet service providers (ISPs).

Question No 13.  TCP/IP comes under which layer in OSI?

TCP/IP and OSI both are not a Layer. Both are reference model.

OSI Reference model.

1.       Application Layer

2.       Presentation Layer

3.       Session Layer

4.       Transport layer

5.       Network Layer

6.       Data link layer

7.       Physical layer

TCP/IP reference model.

1.       Application Layer

2.       Transport Layer

3.       Internet Layer

4.       Data link layer

5.       Physical layer

In another word, the TCP/IP work between the Network and Transport layer. Because, TCP comes under Transport Layer & IP comes under Network Layer.

Question No 14.  Give one example where STP should be used on a network?

By default STP used, when you have a redundant link between the switches.

Question No 15.  If a switch reboots, will the mac-address table on it be retained?

Static mac- address-table entry will be retained and dynamic learned mac address will be removed.

Question No 16. Provide one limitation of access control lists?

• You cannot see what ACL line was matched by a packet 
• ACLs do not affect multicast and broadcast traffic that is forwarded from or to the access points (APs) and wireless clients 

• ACLs are processor dependent and can impact the performance of the controller under heavy load.

Question No 17. Should the DNS server and default gateway on a PC be the same?

Possible: Can enable the dns server on your gateway ip. Then both gateway ip and dns remain same.

Question No 18. Is a gateway required to be configured on a PC to ping the gateway.

No need

Question No 19. What is the difference between NAT and proxy server.

Assume that, there are two organizations. Organization 1 using internet with a NAT device . Organization 2 using internet with Proxy server.

Organization 1 : Assume that the default gateway address of the TCP/IP adapter setting of the users PC is configured with the IP address of the NAT device. At organization 1, when a user attempts to access a device on the internet through any protocol like HTTP, FTP, Ping, Telnet etc, the IP packet carrying the traffic would be sent to the default gateway and NAT applied on the packet. When NAT is applied , the source IP address of the IP packet generated by the user would be re-written with the IP address of the NAT device irrespective of the type of protocol. So all IP packets would be translated and most types of IP traffic can flow through NAT.

Organization 2: The default gateway configured on the TCP/IP adapter settings of the Users PC is the Proxy Servers IP address. Additionally, the browser is also configured with the Proxy Servers IP address. When a user initiates HTTP traffic ( Typing a URL on the browser ), the request would be sent to the Proxy server and the source IP address of the IP packet would be re-written with the Proxy Servers IP address. What would happen if the user tries to FTP or Ping a device which is on the internet ? The request goes to the proxy server, because the default gateway is the proxy servers IP address. But when the packet reaches the Server, it does not have the capacity to re-write the source, because the proxy server supports only packets carrying HTTP traffic. This is why also other packets apart from HTTP are dropped.

Question No 20. What is the Difference between HTTP and HTTPS?

Difference between HTTP and HTTPS:

 i. URL begins with “http://" in case of HTTP while the URL begins with “https://” in case of HTTPS.
ii. HTTP is unsecured while HTTPS is secured.
iii. HTTP uses port 80 for communication while HTTPS uses port 443 for communication.
iv. HTTP operates at Application Layer while HTTPS operates at Transport Layer.
v. No encryption is there in HTTP while HTTPS uses encryption.
vi. No certificates required in HTTP while certificates required in HTTPS.