109.3 Basic Network Troubleshooting

Question 1

DNS lookup utility for troubleshooting DNS issues, options use the + sign.

Answer 1

dig [ global options ] host [ local options ]

Ex. dig +noall +answer MX linux.com

Question 2

Ping command for IPv6.

Answer 2

ping6

Question 3

Traceroute command for IPv6.

Answer 3

traceroute6

Question 4

Tracepath for IPv6.

Answer 4

tracepath6

First column shows TTL.

Question 5

Can be used to get the host name from an IP address or the IP address from a host name.

Answer 5

host 66.6.44.4

host kmauthorized.com

Question 6

Enables or disables receiving multicast packets on the network interface.

Answer 6

ifconfig [-]allmulti

Question 7

Sets promiscuous mode.

Answer 7

ifconfig eth0 -promisc

Question 8

Flush all IP addresses from the 192.168.1.0 network.

Answer 8

ip -s a f to 192.168.1.0/24

Question 9

Get additional statistics about the IP network.

Answer 9

ip -s -s

Question 10

Remove 192.168.1.151 from the eth0 interface.

Answer 10

ip a del 192.168.1.151/24 dev eth0

Question 11

Bring eth0 down and back up again.

Answer 11

ip link set eth0 down

ip link set eth0 up

Question 12

Flush protocol addresses.

Answer 12

ip eth0 flush

Question 13

A simplified version of traceroute, determines MTU, no need for superuser privileges.

Answer 13

tracepath

Question 14

Changes made to the routing table using which command are temporary?

Answer 14

route

Question 15

Reads and writes data across network connections using TCP or UDP.

Answer 15

netcat

Question 16

Command to temporarily change the hostname.

Answer 16

hostname -b

Question 17

Full path to conf file to permanently change the hostname.

Answer 17

/etc/hostname

/etc/sysconfig/network (on older Fedora-based systems)

Question 18

Location of BOOTPROTO, IPADDR, NETMASK on Fedora-based systems.

Answer 18

/etc/sysconfig/network-scripts/

Question 19

Command to enable IP forwarding on a CentOS system.

Answer 19

echo 1 > /proc/sys/net/ipv4/ip_forward

Question 20

Full path to check state of eth0 after ifup command, and if empty, this indicates that another utility was used to bring up eth0.

Answer 20

/run/network/ifstate