Nslookup is used to find details related to a Domain name server. Details like IP addresses of a machine, MX records, servers etc. It sends a domain name query packet to the corresponding DNS.
Nslookup has two modes. Interactive and non interactive. Interactive mode allows the user to interact by querying information about different hosts and domains.
Non interactive mode is used to fetch information about the specified host or domain.
Interactive mode:
Nslookup [options] [server]
What is Bash Shell?
Bash is a free shell for UNIX.
It is the default shell for most UNIX systems. It has a combination of
the C and Korn shell features. Bash shell is not portable. any Bash specific
feature will not function on a system using the Bourne shell or one of
its
replacements, unless bash is installed as a secondary
shell and the script begins with #!/bin/bash. It supports regular and expressions.
When bash script starts, it executes commands of different scripts.
Explain Some Network-Monitoring Tools in Linux: ping, traceroute, tcpdump, ntop.
Network monitoring tools are used to monitor the network, systems present on the network, traffic etc.
Ping: Ping command is used to check if the system is in
the network or not. To check if the host is operating.
e.g. ping ip_address
When the command is executed, it returns a detailed summary of the host. Packets sent, received, lost by estimating the round trip time.
Traceroute : the command is used to trace the path taken
by the packet across a network. Tracing the path here means finding out
the hosts visited by the packet to reach its destination. This information
is useful in debugging. Roundtrip time in ms is
shown for every visit to a host.
Tcpdump: commonly used to monitor network traffic. Tcdump captures and displays packet headers and matching them against criteria or all. It interprets Boolean operators and accepts host names, ip address, network names as arguments.
Ntop : Network top shows the network usage. It displays
summary of network usage by machines on the network in a format as of UNIX
top utility. It can also be run in web mode, which allows the display to
be browsed with a web browser. It can
display network traffic statistics, identify host etc.
Interfaces are available to view such information.
