PING : NETWORK TROUBLESHOOTER

Network Diagnostic tool

#Ping uses timed IP/ICMP ECHO_REQUEST and ECHO_REPLY packets to probe the "distance" to the target machine and since it's inception it's been part of Berkeley UNIX, many OS like Microsoft, Mac OS

Ping [Packet InterNet Grouper] can be very useful Internet network diagnostic tests.

Steps to be followed while troubleshooting Network Issue's

Ping the localhost: Ping to 127.0.0.1 address will always ping yourself,  

1)  You can check  Ethernet adapter is Fine or Malfunctioning.

2)  Also check  TCP/IP Stack is installed on local PC 

Ping the Default Gateway: Ping to default gateway address will always network interface is up and has default route ( you can get Default gateway in ifconfig or ipconfig command )

1) Incase ICMP is blocked using firewall you cannot get response back. 

Ping to Check Internet / Intranet servers:  Ping to see if you can reach another computer internet / intranet (8.8.8.8 google DNS server).

1) You test whether host is alive and current time taken to respond back to ping. 

Ping to check domain is UP & Get Domain IP address :  Ping can be used to probe domain is UP and get domain IP address.

1) Check whether domain is up. 

2) You can get the IP address of the domain.

Ping Life Cycle: You can use the Ping command to determine how long it takes to bounce a packet off of another site, which tells you its Internet distance in network terms

1. Source sends an ICMP ECHO_REQUEST to the destination.
   
2. Ping program initialize an SEQUENCE ID which increments with each ICMP ECHO_REQUEST
   
3. Ping initializes TTL (Time-to-live) period.
   
4. Ping also inserts the sending time in the data section of the ECHO_REQUEST.
   
5. Ping calculates ROUND_TRIPTIME, when host is responds with ICMP ECHO_REPLY back to the source.
   
6. Ping with new ICMP ECHO_REQUEST increments the sequence identifier till user specified or default.

Ping statistics: Ping percentage of packet loss  number of packets transmitted, number of packets received, percentage of packet loss & round-trip time minimum, average and maximum.

Aliases - First thing to setup in Linux

Aliases are best made tools for making your life simpler in Linux.

You can set it temporarily ( session based )  or Permanent( edit /etc/bashrc ) or User specific( edit ~/.bashrc )

It reduces the typing effort of commands or groups of commands that are long and/or tedious to type.

Commands :  

# alias  name=' very big command with arg1 arg2...' 

# alias  name='script.sh' 

# alias dir="ls -al | grep ^d" 

# alias p="pwd"; l="ls -al"  

aliases can be used to increase the safety of the system by making commands interactive.

# alias rm="rm -i" 

# alias cp="cp -i"   

You can create your own user friendly commands

# alias dir="ls -al | grep ^d"  

Removing Aliases

# unalias rm  
# unalias cp