A Technical I.T./DevOps Blog
Problem scenario
You are concerned you have an older, vulnerable version of OpenSSH. What command should you run to see what version you are using?
Solution
ssh -V
Versions from 4.4p1 up to, but not including, 8.5p1 are not vulnerable due to a transformative patch for CVE-2006-5051, which made a previously unsafe function secure.
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Continue reading “What Is The Command to Find What Version of SSH You Are Using?”
Problem scenario
You want to direct traffic to web servers (e.g., duplicative, stateless web servers). You want to do it without a load balancer (as they can become a bottleneck). What technologies could you use?
Possible Solution #1
Use Round Robin DNS. This DNS system can send traffic to a list of web servers. See more on cloudflare.com.
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Continue reading “How Do You Distribute Traffic to Web Servers without a Load Balancer?”
Problem scenario
RDP is not allowing you to log into a Windows Server. What should you do?
Possible Solutions (that can be followed in random order)
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Problem scenario
You get an error about insufficient IP addresses. You have exhausted a pool of IP addresses but you do not understand why. What could be wrong when you have no spare IP address, or you get a message related to this problem when you do not think that there is a shortage?
Possible Solution
You were doing an upgrade with a “rolling” option such that there was no downtime.
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Continue reading “How Do You Troubleshoot Not Having Enough IP Addresses?”
Problem scenario
You are not sure if an email address is associated with spam. Someone make comments on your blog. You are not sure if they are legitimate comments or if it is someone trying to spam a website or create a message that is an advertisement. What should you do to check-in on the email address?
Solution
Try https://cleantalk.org/blacklists/
On cleantalk.org you can search for IP addresses,
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Problem scenario
You read that a gateway was directing web traffic to a specific IP address or endpoint. Can a gateway forward HTTP/HTTPS traffic?
Solution
Yes.
Gateways are a type of router. Routers connect two or more networks and provide the routing function.
https://www.ibm.com/docs/fr/aix/7.2?topic=routing-tcpip-gateways
Gateway describes a load balancer operating at the edge of the mesh receiving incoming or outgoing HTTP/TCP connections.
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Continue reading “Can a Networking Gateway Redirect Internet Traffic to a Different Destination?”
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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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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Continue reading “How Do You Architect a System without DNS Being a Single Point of Failure?”
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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Continue reading “How Do You Get a USB-to-Ethernet Cable to Work with Linux?”
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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Continue reading “How Are Backoff Strategies (with Client Retries) Helpful?”