The Router Log Level directive is used by the sys log server to specify the level of severity of the log. This directive is used to control the types of errors that are sent to the error log by constraining the severity level. Eight different levels are present in the Log Level directive, which are shown below in order of their descending significance: Number Level Description 0emergEmergencies - system is unusable 1alertAction must be taken immediately 2critCritical Conditions 3errorError conditions 4warnWarning conditions 5notice Normal but significant condition 6infoInformational 7debug Debug-level messages Note: When a certain level is specified, the messages from all other levels of higher significance will also be reported. For example, when Log Level crit is specified, then messages with log levels of alert and emerg will also be reported.

Dsniff is a set of tools that are used for sniffing passwords, e-mail, and HTTP traffic. Some of the tools of Dsniff include dsniff, arpredirect, macof, tcpkill, tcpnice, filesnarf, and mailsnarf. Dsniff is highly effective for sniffing both switched and shared networks. It uses the arpredirect and macof tools for switching across switched networks. It can also be used to capture authentication information for FTP, telnet, SMTP, HTTP, POP, NNTP, IMAP, etc. Answer option B is incorrect. Cain is a multipurpose tool that can be used to perform many tasks such as Windows password cracking, Windows enumeration, and VoIP session sniffing. This password cracking program can perform the following types of password cracking attacks: Dictionary attack Brute force attack Rainbow attack Hybrid attack Answer options D and C are incorrect. These tools are port scan detection tools that are used in the Linux operating system.

The Common Gateway Interface (CGI) is a standard protocol for interfacing external application software with
an information server, commonly a Web server. The task of such an information server is to respond to
requests (in the case of web servers, requests from client web browsers) by returning output. When a user
requests the name of an entry, the server will retrieve the source of that entry's page (if one exists), transform it
into HTML, and send the result.
Answer option A is incorrect. DHCP is a Dynamic Host Configuration Protocol that allocates unique (IP)
addresses dynamically so that they can be used when no longer needed. A DHCP server is set up in a DHCP
environment with the appropriate configuration parameters for the given network. The key parameters include
the range or "pool" of available IP addresses, correct subnet masks, gateway, and name server addresses.
Answer option B is incorrect. The Internet Protocol (IP) is a protocol used for communicating data across a
packet-switched inter-network using the Internet Protocol Suite, also referred to as TCP/IP.IP is the primary
protocol in the Internet Layer of the Internet Protocol Suite and has the task of delivering distinguished protocol
datagrams (packets) from the source host to the destination host solely based on their addresses. For this
purpose, the Internet Protocol defines addressing methods and structures for datagram encapsulation. The
first major version of addressing structure, now referred to as Internet Protocol Version 4 (IPv4), is still the
dominant protocol of the Internet, although the successor, Internet Protocol Version 6 (IPv6), is being deployed
actively worldwide.
Answer option D is incorrect. Transmission Control Protocol (TCP) is a reliable, connection-oriented protocol
operating at the transport layer of the OSI model. It provides a reliable packet delivery service encapsulated
within the Internet Protocol (IP). TCP guarantees the delivery of packets, ensures proper sequencing of data,
and provides a checksum feature that validates both the packet header and its data for accuracy. If the
network corrupts or loses a TCP packet during transmission, TCP is responsible for retransmitting the faulty
packet. It can transmit large amounts of data. Application layer protocols, such as HTTP and FTP, utilize the
services of TCP to transfer files between clients and servers.

Nmap
Explanation:
Nmap is a free open-source utility for network exploration and security auditing. It is used to discover computers and services on a computer network, thus creating a "map" of the network. Just like many simple port scanners, Nmap is capable of discovering passive services. In addition, Nmap may be able to determine various details about the remote computers. These include operating system, device type, uptime, software product used to run a service, exact version number of that product, presence of some firewall techniques and, on a local area network, even vendor of the remote network card. Nmap runs on Linux, Microsoft Windows, etc.