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Network Configuration and Troubleshooting

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1. ifconfig command

ifconfig (interface configurator) command is use to initialize an interface, assign IP Address to interface and enable or disable interface on demand. 

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> ifconfig

# ifconfig with interface (eth0) command only shows specific interface
> ifconfig eth0

# Assigning an IP Address and Gateway to interface on the fly. The setting will be removed in case of system reboot.
> ifconfig eth0 192.168.50.5 netmask 255.255.255.0

# enable Specific Interface
> ifup eth0

# disable Specific Interface
> ifdown eth0

# set MTU Size
> ifconfig  eth0 mtu xxx

# set Interface in Promiscuous mode
# Network interface only received packets belongs to that particular NIC. If you put interface in promiscuous mode it will received all the packets.
> ifconfig eht0 - promisc

2. ping command

PING (Packet INternet Groper) command is the best way to test connectivity between two nodes. Whether it is Local Area Network (LAN) or Wide Area Network (WAN). Ping use ICMP (Internet Control Message Protocol) to communicate to other devices. You can ping host name of ip address using below command.

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> ping ip
> ping domainName
> ping -c times  ip/domainName

3. traceroute command

traceroute is a network troubleshooting utility which shows number of hops taken to reach destination also determine packets traveling path.

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> traceroute 4.2.2.2

4. NETSTAT command

Netstat (Network Statistic) command display connection info, routing table information etc. To displays routing table information use option as -r.

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> netstat -r

5. dig command

dig (domain information groper) query DNS related information like A Record, CNAME, MX Record etc. This command mainly use to troubleshoot DNS related query.

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> dig domainName

6. nslookup command

nslookup command also use to find out DNS related query.

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> nsloopup domainName

7. route command

route command also shows and manipulate ip routing table.

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> route

# add route
> route add -net 10.10.10.0/24 gw 192.168.0.1

# delete route
> route del -net 10.10.10.0/24 gw 192.168.0.1

# add default GateWay
> route add default gw 192.168.0.1

8. host command

host command to find name to IP or IP to name in IPv4 or IPv6 and also query DNS records.

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> host domainName

# Using -t option we can find out DNS Resource Records like CNAME, NS, MX, SOA etc.
> host -t domainName

9. arp command

ARP (Address Resolution Protocol) is useful to view / add the contents of the kernel’s ARP tables.

查看局域网所有IP地址的设备,且获取相应的MAC

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> arp -a

10. hostname command

hostname is to identify in a network. Executhostname command to see the hostname of your box. You can set hostname permanently in /etc/sysconfig/network. Need to reboot box once set a proper hostname.

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> hostname

11. GUI tool system-config-network

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> system-config-network

12. ethtool command

ethtool is a replacement of mii-tool. It is to view, setting speed and duplex of your Network Interface Card (NIC). You can set duplex permanently in /etc/sysconfig/network-scripts/ifcfg-eth0 with ETHTOOL_OPTS variable.

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> ethtool eth0

13. iwconfig command

iwconfig command in Linux is use to configure a wireless network interface. You can see and set the basic Wi-Fi details like SSID channel and encryption. You can refer man page of iwconfig to know more.

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> iwconfig [interface]
> man iwconfig

Reference

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