Friday, 7 October 2011

Network Utilities

Most of the available networking tools are specialized and are mainly of interest to professionals who are maintaining a large network. Many, however are relevant to the Internet and some of these can be helpful to the average PC user. The commands in the first table are generic and in general, with some minor exceptions, apply across each operating system.

Generic Network Utilities
ping <target_name>
Verifies IP-level connectivity. This utility verifies that a host computer can connect to the TCP/IP network and network resources.
ipconfig /all

# Renew IP addr. config
ipconfig /renew

# Release IP addr. config
ipconfig /release
Display TCP/IP configuration information, renew and release DHCP assigned address configuration and register in dynamic DNS or flush the local DNS cache.

The *nix equivalent of this command is usually ifconfig
# Display current ARP entries
arp -a

# Add a permanent ARP entry
arp –s <inet_addr> <eth_addr>

# Delete host
arp –d <inet_addr>
The arp utility can be used to manually resolve IP addresses to MAC addresses and to modify or display the current ARP cache table.
# Display current connection and listening ports
netstat -a

# Display Ethernet stats
netstat –e

# Displays routing table
netstat –r
Display TCP/IP protocol statistics and information about TCP and UDP connection to and from the local computer.
tracert <target_name>

# Do not resolve addresses
tracert –d <target_name>
Determine the route that an IP datagram takes to reach a destination.

For the more advanced users, we can add more powerful commands to our networking toolbox. The below commands are mostly of use to *Nix (in particular Linux) users whereby most of the things can be performed through scripts.  

Specific Networking Utilities
# Check if iptables is running
service iptables status

# Disable iptables
service iptables stop
# First IP
ifconfig eth0:0 netmask

# Second IP
ifconfig eth0:1 netmask
Assign multiple IP addresses
ifconfig eth0 hw ether 00:01:02:03:04:05
Change MAC address

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