ping ss route netstat command

Useful command To Checking Connectivity of Network  -

• ping

• ss

• netstat

• route

• tcmpdump

• wireshark

• munin

• cacti

Ping - to use ping command for checking IP or host or network is reachable or not

Ex-  ping < network )

# ping  10.10.10.1 

SS - socket statistics  - to know all information about TCP/UDP Connection , Established Connection  , protocol , TCP socket etc.

# ss 

Option

-a = Display all info

-l = Display all open port/socket

-o = Show time info

-m = Show memory info

-p = Show process info

-i = Show internet TCP/IP information

-r = Resolve host name

-4 = Display only IPv4 socket

-6 = Display only IPv6 socket

Netstat - t o see the information about network connection , routing table , interface etc.

# netstat

Option

-t   = display all tcp connection

-u  = display all UDP connection

-r  = display all routing table

-s =  display networking statistics

-v = verbos mode

-l   = list all open socket

-a = all

-o = display time

route   =  to see the routing table  , add new route etc

# route

Option

-v, --verbose           be verbose

-n, --numeric          don t resolve names

-e, --extend            display other/more information

-F, --fib                  display Forwarding Information Base (default)

-C, --cache            display routing cache instead of FIB

To add default getaway

# route  add  default  gw  10.10.10.1

To set route for 2 different network

For example , we have 2 eth one is direct broadband connection establish by modem  & second eth1 we gave IP 10.10.10.100 & netmask 255.255.0.0 we do not give gateway

To add route command

#route  add  -net < network>  netmask <netmask>  gw <getaway>

Ex - # route  add  -net  10.10.20.0  netmask  255.255.0.0  gw 10.10.10.1 

Ex - # route  add  -net  10.10.30.0  netmask  255.255.0.0  gw 10.10.10.1 

To reject particular host/IP/Network

# route add -host  10.10.10.200  reject

Tcmpdump - is an command-line packet capture and analyzer tool for monitoring network traffic.

# yum install tcpdump

Command

# tcpdump

Specific interface

# tcpdump -i eth0

Display Available interface

# tcpdumb -D

Capture packet in ASCII Format

# tcpdump -A -i eth0

Capture packet in HEX & ASCII Format

# tcpdump -XX -i eth0

Capture packet & save in file : here *.pcap is file format

# tcpdump -w 0001.pcap -i eth1

Read capture packet file

# tcpdump -r 0001.pcap

Capture IP Address Packet

# tcpdump -n -i eth0

Capture TCP Packet

# tcpdump -i eth0 tcp

Capture packet form specific port

# tcpdump -i eth0 port 22

Capture packet form source IP

# tcpdump -i eth0 src 10.20.2.33

Capture packet form Destination IP

#tcpdump -i eth0 dst 10.20.2.126

Wireshark - is an open source network protocol analyzer that is used to troubleshoot network related issues.

# yum install wireshark*

Munin - is an web based network and system monitoring application that is used to display results in graphs using rrdtool.