How Do You Architect a System without a Load Balancer Being a Single Point of Failure?

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Problem scenario
You want to design a system without a single point of failure. How can you ensure a load balancer is not a single point of failure?

Solution
Have DNS route to two or more load balancers. DNS does not know the back-end servers’ or pods’ health statuses, according to a StackOverflow.com posting. Therefore you would want to configure the TTL governing the networking of the DNS to be short to ensure DNS services are aware of a web server that is down (according to a Quora posting).

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How Do You Architect a System without DNS Being a Single Point of Failure?

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Problem scenario
You want to design a system without a single point of failure. How can you ensure a DNS is not a single point of failure?

Solution
Have multiple authoritative DNS servers. To read more, see Networkworld or Medium. We observe that one tradeoff is there is not a single source of truth, but the benefit is that you do not have a single point of failure.

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How Do You Get a USB-to-Ethernet Cable to Work with Linux?

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Problem
You connect a USB convertor (for a wired ethernet cable) to your Linux laptop. It isn’t working as a plug-and-play device. What could be wrong?

Solution
1. In the GUI on the Linux desktop, go to “Settings” or “Control Settings”. 2. Then go to “Network”.
3. Click a plus sign “+” (to add a new profile).
4. On the Identity tab,

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How Are Backoff Strategies (with Client Retries) Helpful?

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Question
Sometimes a client attempts to connect to or use an application. Sometimes a Kubernetes Pod is being created and tries to pull down an image. Sometimes a network device tries to establish a connection to an endpoint. These attempts can initially fail. Retries can be attempted in rapid succession. To mitigate excessive attempts in a short amount of time (to not waste resources or cause a denial-of-service attack),

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How Do You Get a NIC on a Linux Server to Work?

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Problem scenario
Your NIC on your Fedora Linux server totally will not work. The physical NIC has no lights on it. It seems it is disabled. You cannot enable it with commands.

You see errors like these in logs: “NetworkManager.service: Start request repeated too quickly.”

What should you do?

Solution
Run this command:

journalctl -u NetworkManager

Do you see lines like these?

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How Do You Get a NIC to Permanently Be in a firewalld Zone with a Single Command?

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Problem scenario
A NIC or network interface is not being protected by a zone in the firewalld. You run firewall-cmd commands, and later run “firewall-cmd –runtime-to-permanent” afterward. But a NIC (e.g., a virtual NIC) will not persistently remain in a zone. You want your firewall-cmd commands to have a permanent effect. The “firewall-cmd –runtime-to-permanent” command is supposed to work, but it is not helping. What should you do?

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How Do You Get a NIC to Permanently Be in a firewalld Zone with Multiple Commands?

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Problem scenario
A NIC or network interface is not being protected by a zone in the firewalld. You run firewall-cmd commands with different flags, but some NIC (e.g., a virtual NIC) will not persistently remain in a zone. You want your firewall-cmd commands to have a permanent effect. The –permanent flag is supposed to work, but it is not helping. What should you do?

Solution
If a firewall-cmd command fails with a –permanent flag,

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Should You Disable WPS on Your WiFi/Router at Home?

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Problem scenario
You want to not broadcast your home’s network (e.g., to make sure people do not borrow your bandwidth or hack your devices such as your thermostat with ransomware). You want to keep using your WiFi. You try to disable the “Broadcast Network Name (SSID)”, but you get a prompt like “WARNING:
Disabling Broadcast Network Name (SSID) will disable Wi-Fi Protected Setup (WPS) functionality. Are you sure you want to change?”

Should you click “OK”?

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How Do You Troubleshoot an IP Address That You Can SSH to, But You Cannot Ping It?

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Problem scenario
nmap shows that the host seems down. You cannot ping the IP address. But you can SSH to the IP address. How is this possible?

Solution
Possible Solution #1
A host server could have multiple IP addresses (e.g., with a virtual server hosted by a type 2 hypervisor utilizing KVM or QEMU). The networking could be done at the kernel level.

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