A Linux systems administrator needs to persistently enable IPv4 forwarding in one of the Linux systems. Which of the following commands can be used together to accomplish this task? (Choose two.)
A.
sysctl net.ipv4.ip_forward
B.
sysctl -w net.ipv4.ip_forward=1
C.
echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf
D.
echo 1 > /proc/sys/net/ipv4/ip_forward
E.
sysctl –p
F.
echo "net.ipv6.conf.all.forwarding=l" >> /etc/sysctl.conf
Correct answer is C and E. C changes the config file (which is read each time on boot) and E loads it immediately.
B (sysctl -w net.ipv4.ip_forward=1) make the change immediately but does not persist. it's wrong.
To persistently enable IPv4 forwarding in a Linux system, you typically need to modify the system configuration files. The two commands you can actually use together to accomplish this task are:
C. echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf: This appends the configuration net.ipv4.ip_forward=1 to the /etc/sysctl.conf file, which will enable IPv4 forwarding persistently across reboots.
E. sysctl –p: This command reloads the sysctl settings from the configuration files, including /etc/sysctl.conf, so that the changes take effect immediately without needing a system reboot.
So the correct combination of commands is C and E. They ensure that IPv4 forwarding is enabled persistently and immediately without requiring a reboot.
B & C accomplish the same goal: write 'net.ipv4.ip_forward=1' to '/etc/sysctl.conf'. (And whatever is in '/etc/sysctl.conf' gets used persistently.) (A) prints the current value of 'net.ipv4.ip_forward'. (D) turns on IPv4 forwarding temporarily (e.g.: gone after reboot). (E) reads 'sysctl' configuration file(s). (F) relates to IPv6, not IPv4 in the question.
C. echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf E. sysctl –p
The command echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf[C] is used to add the line net.ipv4.ip_forward=1 to the /etc/sysctl.conf file. This line enables IPv4 forwarding when the system boots.
The command sysctl –p[E] is used to reload the sysctl settings from the /etc/sysctl.conf file. This makes the changes take effect immediately without requiring a system reboot.
Option B, sysctl -w net.ipv4.ip_forward=1, does enable IPv4 forwarding, but it does not persist after a system reboot. This command changes the runtime settings of the system, which are reset to their default values when the system is rebooted.
On the other hand, Option C, echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf, writes the setting into the /etc/sysctl.conf file, which is read at boot time. This makes the change persistent across reboots.
Option E, sysctl –p, is used to reload the sysctl settings from the /etc/sysctl.conf file immediately, without needing to reboot the system. This is why options C and E are chosen for persistently enabling IPv4 forwarding.
C. echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf
This command adds the net.ipv4.ip_forward=1 line to the /etc/sysctl.conf file, which will be read during system startup.
E. sysctl –p
This command is used to apply changes from the sysctl configuration file, including the changes made in /etc/sysctl.conf. It makes sure that the changes take effect without requiring a system restart.
Alot of people are putting BC and I thought I agreed with it until I looked closer at the question, and I found 2 things wrong with BC
1. B doesnt actually make it persistent across system reboots only C does that
2. The question asks what commands can be used together, seems odd to run these commands together
C and E however
C. will turn on ipv4 forwarding via appending it to the /etc/sysctl.conf file
D. will apply and reload the changes without a reboot of the system
The commands that can be used together to persistently enable IPv4 forwarding in a Linux system are:
C. echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf
E. sysctl –p
The first command echo "net.ipv4.ip_forward=1" >> /etc/sysctl.conf is used to add the net.ipv4.ip_forward=1 line to the end of the /etc/sysctl.conf file. This file is used to configure kernel parameters at runtime. The change made in this file will persist across reboots.
The second command sysctl –p is used to apply the changes made to the /etc/sysctl.conf file. It reloads the configuration file and sets the new values for the specified parameters.
The other options sysctl net.ipv4.ip_forward, sysctl -w net.ipv4.ip_forward=1, echo 1 > /proc/sys/net/ipv4/ip_forward, and echo "net.ipv6.conf.all.forwarding=l" >> /etc/sysctl.conf are not suitable for persistently enabling IPv4 forwarding, as the changes made with these commands will not persist after a reboot.
The correct options to persistently enable IPv4 forwarding in Linux are C and E.
Option C adds the line "net.ipv4.ip_forward=1" to the file /etc/sysctl.conf which is used to configure kernel parameters at boot time. This ensures that IPv4 forwarding is enabled each time the system starts.
Option E is used to reload the sysctl configuration from the /etc/sysctl.conf file, which in turn sets the IPv4 forwarding value to 1 as specified in the configuration file.
1.to allow persistent IPv4 packet forwarding: sysctl -w net.ipv4.ip_forward=1
2. Once the system is satisfactorily tuned, make the new values permanent by modifying /etc/sysctl.conf or the /etc/sysctl.d/ directory.
Even in your used link it states:
Using either method above will not make the change persistent. To make sure the new setting survives a reboot, you need to edit the /etc/sysctl.conf file.
# sudo nano /etc/sysctl.conf
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