Need some advice on learning networking

[slimslob]

Re: Need some advice on learning networking

I am officially done with reviewing material. It was quite beneficial. I'm exactly at the 50% mark in terms of overall progress. It's amazing to me that I've put in this much time and effort and I'm only half way done.

Because CCNA is vendor specific, they can drill down to specifics unlike some other vendor neutral certificates.

Earlier today I previewed my next chapter which is: Hot Standby Router Protocol. What is this, you ask?

In a small to medium network, you have a single Internet Service Router and 1 edge router. But in a production network, you're gonna have 2 ISP routers and multiple edge routers. In other words, the network will be designed to have no single point of failure. The name of the game is: redundancy redundancy redundancy.


The game plan is to watch a few videos and get an idea of how it works and then to do a deep dive into the protocol. It's looks complicated.



EDIT: I've only been watching the first video for about 10 minutes and it's very interesting.

Pro Tip: Best practice is to have 2 Internet Service Provider Routers and make sure they are from 2 different providers. For example, one internet provider should be ATT and the other should be Verizon, for example.

Actually you can still have a single point of failure, the LAN DHCP. I had it happen at a major oilfield engineering company, DHCP service went down over night. Everyone who turned their computer over night had no access to the internet, file servers and printers. Their local IT had been working on the internet access problem thinking it was a router problem. I got called because of the printing problem. It took me less than 5 minutes to find there was no DHCP. Their local IT was too busy to talk to me so the receptionist contacted the corporate IT who called me. I told him what I found.

[BillyCarpenter]

Re: Need some advice on learning networking

Actually you can still have a single point of failure, the LAN DHCP. I had it happen at a major oilfield engineering company, DHCP service went down over night. Everyone who turned their computer over night had no access to the internet, file servers and printers. Their local IT had been working on the internet access problem thinking it was a router problem. I got called because of the printing problem. It took me less than 5 minutes to find there was no DHCP. Their local IT was too busy to talk to me so the receptionist contacted the corporate IT who called me. I told him what I found.

In the topology that I'm talking about, the only single point of failure that you can have is at the access switch (the switch that the PCs plug into). All of the distribution and core switches are redundant. Ditto for the routers. In other words, if one goes down, there's still a path to connectivity. Likewise, if one internet router goes down, it will automatically switch to the other ISP router.


EDIT: I understand what you're saying. You're talking about the DHCP Server. While that's true, it's not relevant when designing a network with routers and switches.

[BillyCarpenter]

Re: Need some advice on learning networking

I've discovered many cool things that routers and switches can do. Maybe one of the coolest is the Hot Standby Routing Protocol.

Imagine that we we work in IT for a large national corporation and much of the business is dependent on the cloud/internet. It is critical that they have connectivity to internet. So, what do we do to ensure that they have internet access at all times?

First we tell them that they need an internet account with 2 major internet companies. Now we have 2 internet routers. Wait a minute....we can only have 1 default gateway on our PC. Even if had 2 NIC cards on our PC, that's not gonna work in a large domain network.

So, what if one of the internet routers goes down? What are we gonna do? Are we gonna go to every PC and change the default gateway to the ISP router that is still up? That's not gonna work.


What do we do?


Enter the HOT STANDBY ROUTER.


Anyone have any idea of how this is gonna work?

[BillyCarpenter]

Re: Need some advice on learning networking

I've been dreading learning Spanning Tree. It's used to prevent broadcast loops at Layer 2 (switch). This is one of those protocols that is extremely complicated and hard to learn.

Thus far here are the 2 hardest to learn protocols:

1. Spanning Tree
2. OSPF

[BillyCarpenter]

Re: Need some advice on learning networking

I once compared a network engineer to being a plumber. Actually, I read that somewhere. I kinda got where they were coming from but was unsure of the comparison. Now I'm sure of it. Being a network engineer today is like being a plumber back in 1950.


Don't misunderstand, I'm not saying that it's easy to learn. In fact, it's very difficult to learn for the majority. "Majority" being the key word. Everything is relevant. The majority of people are of average intelligence, myself included. So, learning these protocols that were written by people much smarter than us is very hard for us to understand. But to the people who wrote the protocols, we must seem like dummies.

[slimslob]

Re: Need some advice on learning networking

I h ave found that the problem with Facebook today is that someone was making a change to a router table and made a mistake. Started sending everyone in the wrong direction. Facebook tech staff tried to correct it and ended up making it worse. At least that is the story that is going around Computer Sciences academia.

[rthonpm]

Re: Need some advice on learning networking

Facebook ended up taking all of its associated DNS entries off the core routers of the Internet. Then when they tried to roll back the change, the team couldn't do it because DNS names wouldn't resolve. Complicating matters further, onsite staff didn't have access to the servers to directly make the change at the console.

Taking down a production network is easier than you think!

Sent from my BlackBerry using Tapatalk

[BillyCarpenter]

Re: Need some advice on learning networking

I h ave found that the problem with Facebook today is that someone was making a change to a router table and made a mistake. Started sending everyone in the wrong direction. Facebook tech staff tried to correct it and ended up making it worse. At least that is the story that is going around Computer Sciences academia.

I'm sure that they were using some kind of routing protocol. That's gonna automatically pick the best (fastest) route. However, these routes can be manipulated by manually changing the "cost" of a particular route. Cost is sometimes changed for load balacing reasons. In other words, we don't want all of our traffic going down one path but rather it's better to have 2 paths balance the load.


And, yes, it'd super easy to take down a production network. Even though I'm learning this stuff, it's more for my own personal enjoyment. I woldn't want to do it for a job. Too much pressure.

[BillyCarpenter]

Re: Need some advice on learning networking

PS - Whomever took down that network will be in the unemployment line. Can you image being THAT guy?

[rthonpm]

Re: Need some advice on learning networking

PS - Whomever took down that network will be in the unemployment line. Can you image being THAT guy?

I reached out to a long time network engineer that I've known for years to ask his opinion on this. He admitted that this type of misconfiguration happens more often than most people think. The only difference in this case is that it was such a large company, and the split of duties didn't allow someone onsite to deal with the issue.

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[BillyCarpenter]

Re: Need some advice on learning networking

I reached out to a long time network engineer that I've known for years to ask his opinion on this. He admitted that this type of misconfiguration happens more often than most people think. The only difference in this case is that it was such a large company, and the split of duties didn't allow someone onsite to deal with the issue.

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I've watched a ton of videos on this type of scenario where a switch or router is misconfigured. Most of the time the router/switch that's being configured is at a remote location and it's easy accidentally configure the wrong piece of equipment.

For the record, I also read that Facebook are building their own routers. At least some of 'em.

[slimslob]

Re: Need some advice on learning networking

I reached out to a long time network engineer that I've known for years to ask his opinion on this. He admitted that this type of misconfiguration happens more often than most people think. The only difference in this case is that it was such a large company, and the split of duties didn't allow someone onsite to deal with the issue.

Sent from my BlackBerry using Tapatalk

To further complicate matters and delay getting them back up, the offsite personnel who had router access rights needed to go onsite to do so. When they arrived at location,their security ID badges were accepted by the scanners but access also required possession of a physical key for the mechanical lock(s). They had to contact the onsite people to get someone down to the door to let them in.

[BillyCarpenter]

Re: Need some advice on learning networking

Spanning Tree is whack butt I've about got it down.


Spanning Tree is to used to prevent broadcast loops that can bring down the network. You don't have to worry about it if you've only got one connection from one switch to another.


Anyway, whomever came up with Spanning Tree is some kind of mad genius.

First a root bridge is elected. Than a root port. Then the designated ports are elected. It's quite the process and I'm glad I learned it. I still need to practice or I'll quickly forget.

[slimslob]

excellent explanationFacebook shoots own foot, hits Instagram and WhatsApp too - Malwarebytes Labs | Malwarebytes Labs

[BillyCarpenter]

Re: Need some advice on learning networking

excellent explanationFacebook shoots own foot, hits Instagram and WhatsApp too - Malwarebytes Labs | Malwarebytes Labs

I haven't covered BGP and I'm not sure if it's covered in the CCNA course. I briefly looked it up just now and the protocol is the only one that will route over the internet for huge networks. Without knowing how it works, it's impossible (for me) to understand what went wrong.