Networks and Security Questions and Answers

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Networks Security Questions and Answers: Submit Your Question

Q - 1 What is OSPF protocol

Ans- (a) OSPF has two primary characteristics. The first is that the protocol is open, which means that its specification is in the public domain. The OSPF specification is published as Request For Comments (RFC) 1247.

The second principal characteristic is that OSPF is based on the SPF algorithm, which sometimes is referred to as the Dijkstra algorithm, named for the person credited with its creation.

(b)OSPF is a link-state routing protocol that calls for the sending of link-state advertisements (LSAs) to all other routers within the same hierarchical area. Information on attached interfaces, metrics used, and other variables is included in OSPF LSAs. As OSPF routers accumulate link-state information, they use the SPF algorithm to calculate the shortest path to each node.

Ospf: Open Shortest Path First.
It Uses SPF(Dijkstra) algorithm and selects the Loopfree path. It is a purely classless Routing protocol(ie sends mask along with the ip address)
It supports SLSM, VLSM, Discontinuous Networks. and the hope count is Unlimited. It is Having Complex Configuration Including Area, Process id, Wild card mask. The metric used is bandwidth(10raise to8/Bandwidth). Administrative Distance is 110

Q - 2 Explain How do we do authentication with message digest(MD5)? (Usually MD is used for finding tampering of data)

Ans- The unique number will be generated by MD5, if it is tamped with someone, the value will be changed so you know you are tampered

Q - 3 Explain What is meant by port blocking within LAN?

Ans- Restricting the users from accessing a set of services within the local area network is called port blocking.

we,ll give you the fine example its nothing but we have to block the switch port with particular maC address..for example we have 8-port switch ,in that first port we connected a machine that belongs to this mac address {4e5a.23bf.34ae.9a4c} and we block the switch port with this mac address for instance you unplug the original host and plug the other one now your new machine will be prevented from accessing switch port thats the idea.... so if u enabling port blocking command in a switch only particular machine or intented machine allow to use access ,other machine will be restricted... port blocking is used for security purpose...otherwise some intruders enter into your company and destroy your lan with single laptop thats it

Q - 4 Explain What is difference between ARP & RARP? How both of these protocols will work, and where it will use?

Ans- ARP -Meaning of ARP "Address Resolution Protocol", is used to map ip Network addresses to the hardware (Media Access Control sub layer) addresses used by the data link protocol. The ARP protocol operates between the network layer and the data link layer in the Open System Interconnection (osi) model.


RARP-RARP (Reverse Address Resolution Protocol) is a protocol by which a physical machine in a local area network can request to learn its IP address from a gateway server's Address Resolution Protocol (ARP) table or cache. A network administrator creates a table in a local area network's gateway router that maps the physical machine (or Media Access Control - MAC address) addresses to corresponding Internet Protocol addresses. When a new machine is set up, its RARP client program requests from the RARP server on the router to be sent its IP address. Assuming that an entry has been set up in the router table, the RARP server will return the IP address to the machine which can store it for future use. RARP is available for Ethernet, Fiber Distributed-Data Interface, and token ring LANs.

Q - 5 Explain all these questions.
What is classful and classless routing?
Diff bet RIPv1 & RIPv2?
What is multicasting?
What is VLSM?

Ans- Classfull routing protocol is a routing protocol that strictly. follows the classfull IP like IGRP,RIP

Classless Routing A scheme which allocates blocks of Internet addresses in a way that allows summarisation into a smaller number of routing table entries.

classful routing:in this routing only ip addresses are used..subnet mask is not used.due to which it does not support subnetting and vlsm

classless uses subnet mask alos...due to which subnetting and vlsm is possible in this case

Rip v1 is classfull routing protcol
Rip v2 is classless routing protocol

multicasting is sending data(packets) to more than one computers but not all on that network

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