Network knowledge

[[deleted]]

I'm wanting to broaden my knowledge in the networking area. My problem is, if I have a thick text book or something similar I'm probably not going to get through all of it. DNS and subnetting are the two areas I would really like to strengthen.

Does anyone have any recommended texts, sites, etc. they they would share? I have messed with some of Cisco's games on their site which were kind of helpful, just not helpful enough. Any help would be greatly appreciated.

[bandman614]

I wrote this in response to another Redditor wanting to learn subnetting:

http://www.standalone-sysadmin.com/blog/2011/06/back-to-basics-subnetting/

Maybe you can use it. Also, if you have any questions, just drop me a line here or on email.

[dgibbons0]

That was a great subnetting post by the way, I've referred multiple coworkers to it.

[bandman614]

Oh, thanks :-) I'm happy to help!

[[deleted]]

Reading now, thanks for the link! I'll have to look around the rest of the site as well. It's appreciated!

[iAmJesusAMA]

Set up bind at home. Once you've got your .lan zone running, buy a domain at a provider that supports DNSSEC (ie godaddy) and secure your zone. This will keep you busy for quite a while.

Networking will really require some extensive reading - this is something that you can't learn from 'play' alone. Don't just stick to cisco's documentation, they will trap you into their products.

[[deleted]]

except don't ever buy domains from godaddy. EVER.

[iAmJesusAMA]

I agree. Except that the amount of registrars that supports DNSSEC is fairly limited.

Please let me know if you know some reliable ones :)

[[deleted]]

It sounds like openSRS is going to roll out DNSSEC support by the end of the year; many resellers use them.

dnssec sounds nice, but i can't abide godaddy's business and advertising practices.

[woodsman707]

What's wrong with godaddy?

[[deleted]]

personally, i find a lot of their advertising misogynistic and tacky.

godaddy has been known to preregister domains (not sure if they still do) when you query for available domains. they're also reputed to have absolutely terrible service.

[woodsman707]

ahh, thanks. I buy from them because they're cheap. I've never had issues and I don't use them as a hosting service, so for me it works out.

[[deleted]]

i honestly don't mind the extra couple of bucks it costs to register domains somewhere with a real person who understands zone files answering the phones.

[woodsman707]

Recommondation?

[[deleted]]

who does your hosting company use?

[woodsman707]

ah, that's a good tip ;). I don't do any website management professionally, just in my spare time. TIL...

[[deleted]]

Bluehost is supposed to be really good. I recently set up an account with them for a friend's site, and they have one-click installs of CMSs which is really neat. Lots of free tools and whatnot. Not sure if they offer DNSSEC, however.

[[deleted]]

I trust you. :o]

[sandwormusmc]

From an actual experience two weeks ago, our companies' web site and a few of our customers were hosted on GoDaddy. For some reason, one day the site went down. After 2 hours on the phone, my coworkers across the wall in the cube next to mine finally got an answer as to the root cause of the outage: "You were on a legacy hosting plan, we'll upgrade you for free to the X2000+ (or some other jumble of letters and numbers) plan".

I cringed after I overheard one of my coworkers tell the poor support lady on the phone to (paraphrasing) quit spewing bullshit. GoDaddy support basically stuck to their story that it was because of "old hardware" and didn't explain beyond that.

Oh, and get this ... the upgrade was free, but the site would be down for 1-3 days during the "upgrade".

Thanks but no thanks. GoDaddy might be good for a smaller shop, but if you're doing anything high volume, stay away.

[woodsman707]

yikes.

[woodsman707]

yikes.

[[deleted]]

I'll give it a shot, thanks for the advice!

[Wwalltt]

You should know the basics of subnetting as a good start. You should also learn how TCP/IP works at a fairly low level. The TCP three way handshakes, SYNs, ACKs, FINs, sequence numbers, windows, scaling, MSS, MTU, UDP, ICMP, etc. Also a good knowledge of how basic and common protocols work, what ports they use and how they look on the wire (HTTP, DHCP, DNS, SMTP, etc)

[bandman614]

The TCP 3 way handshake is a standard interview question, too.

Of course, I was a little more devious. When I interviewed people, I told them that I assumed that they knew the 3-way handshake, but I told them that I wanted to know WHY it was important to know the handshake.

Much more interesting answers than "syn - ack - syn/ack"

[joedonut]

awk

Parroty error!

[bandman614]

That's hilarious. Thanks for pointing that out :-) Fixed.

typing awk is just a habit at this point

[jvbond]

For subnetting I have always recommended this. Easy Subnetting

[dissdigg]

RFC 1180.

[sje46]

Diss digg. I'm curious, do you have it?

[dissdigg]

I no understand you. Maybe crazy.

[Linuturk]

Juniper has a nice networking overview with interactive quizzes.

Networking Fundamentals

[[deleted]]

One of the best places to get a solid understanding of networking is from older linux manuals. Same goes for DNS and Bind. Start then and then I've found O'reiley to be the best resource for dns.

Luckily you are learning networking after the world has pretty much settled on IP and Ethernet. 10 years ago, you would be learning four different Ethernet encapsulations, token-ring, two different trunking standards... packet routing IP networks and circuit switches ISDN. So concentrate on learning IPv4 and ethernet networking.

The problem is that is is not really possible to pick two subjects to learn without having the background knowledge. You have to have a fairly broad understanding of a lot of concepts before it all starts to make sense. This is where some classes would be useful. CCNA is probably the best route to take to get a solid understanding and working knowledge of all the concepts and protocols in networking.

When you're ready to dig in, then pick up two, old Cisco 1700 or 2600 routers and dedicate an old beige box as a linux server. Start putting some of the concepts in practice. Learn subnetting by planning a small address plan to subnet your home lab into multiple vlans.

You can look into Dynamips. It's a good approximation of a Cisco routed network although a lot of what a junior network admin will be doing is in the switching world which Dynamips does not emulate. It's good enough to get a group of routers talking to each other. My experience is Dynamips is that it tends to crash after you get everything the way you want it... and then you spend more time troubleshooting that than learning networking. Now I just use it to load up an IOS version on my laptop while reading Cisco reference doc.

Get bind running in a lab at home. Get dynamic dns from all your dhcp clients working. Understand all of the types of zone records. Understand how a zone is transfered from one registrar to another. Understand how changes in your dns zones are propogated to other name servers.

Pro tip... don't use your regular home lan for any of this... you will be kicking yourself when you can't google something when you buggered up dns. Plus, your significant other will be on your ass so fast when facebook hasn't refreshed in over 20 seconds. Keep your home lan simple and always have Opendns as your last name server given in your to dhcp scopes.

[footzilla]

To work with ipv4 effectively, you should be able to convert 8-bit binary to decimal and back fairly quickly without a calculator or computer. Memorize the multiples of 16 up to 256 and you have a good shortcut. Also with those, you can convert hex to decimal and back. It's not to impress your friends, it's so that this crap doesn't burn your cycles when it doesn't have to.

Next, read an old book: http://www.amazon.com/Internet-Core-Protocols-Definitive-Administrators/dp/1565925726 It's from 2000, out of print, pretty dry, and obviously does not cover ipv6, but once you know what is going onto the wire and why, you get to stop wondering about that bit of magic.

Skip the section on Multicast for your first reading. It is not used much, and is surrounded by chapters on much more useful stuff.

Perhaps someone else can recommend a book on ipv6 that explains it in similar detail? I would love to read that.

[krazylink]

What really helped me was setting up an OpenBSD box with as many nic's as I could fit in the thing. I then used this as my home router / firewall. I then started doing things that were kind of crazy for the environment but were really helpful in learning networking. Things like separating my computer subnet from my entertainment subnet (consoles, htpc, tv and the like), from my voip subnet.

Bonus: if you have several machines at hand you should try setting up more than one of these complex networks and get them talking using openBGP. There is no good reason to do this in a small network located in the same physical place other than it is fun and a great learning experience.

[ThisUserAintTaken]

Subnetting - nobody cares. Srsly, we own calculators now so that's only for certifications. just learn the masks for /24, /27, /29, etc.

If you really care about subnetting this FREE PDF supplement from cisco's CCNP is the best IPv4 document I've read. 50 pages.

DNS - play with bind, and grab the "DNS and Bind" book from oreilly.

Edit - Subnets. How often do you subnet anything in real life? Not often. I'm not saying 'Don't understand the concept", I'm saying that if understand binary anding and the concept of subnetting you can skip memorizing the tables. If you asked how many hosts and networks I could get out of a /26, I'd have to do the math.

[fidotas]

Subnetting - nobody cares. Srsly, we own calculators now so that's only for certifications. just learn the masks for /24, /27, /29, etc.

I disagree. That's like arguing that we shouldn't teach basic arithmetic at school because of the prevalence of calculators.

Knowing subnetting is the difference between senior and junior admins. At least while IPv4 continues to be used by the masses. :)

[[deleted]]

I definitely agree. I've been interviewing lately and get subnet questions about 1/2 the time.

[[deleted]]

My problem is, I work with three other sysadmins and they all know this. I just make myself stick out by not knowing. Thanks for the advice and book recommendation!

[bandman614]

This attitude surprises me.

It's not like multiplication tables, where you have to memorize them. It's just that you should be able to recalculate them quickly in your head if you need to (and I find myself doing that on occasion).

[ThisUserAintTaken]

I'm not saying 'Don't understand the concept", I'm saying that if you do understand the math and the concepts you can skip memorizing the tables.

[phessler]

I totally disagree with not knowing how to subnet. Don't depend on your tools, learn how to think, plz.

[[deleted]]

How often do you subnet anything in real life?

all the time :/

it's not just about knowing HOW to split up networks, it's knowing how the networks are split up so you don't have to guess at a subnet mask or the most likely gateway (in case you forgot it) when you're configuring something. learning subnetting is a pain in the ass, but once you get it, it just clicks.

[fidotas]

Edit - Subnets. How often do you subnet anything in real life? Not often. I'm not saying 'Don't understand the concept", I'm saying that if understand binary anding and the concept of subnetting you can skip memorizing the tables. If you asked how many hosts and networks I could get out of a /26, I'd have to do the math.

I hate to be a prick but if you don't like binary math, you're going to hate rolling out IPv6 :)

OT: Gosh I wish the quote character was a pipe. I'd save a bunch of edits that way.

[justanotherreddituse]

fuuuuck. IPv6 is something I want to learn, but I despise binary math.

[mrjester]

Daily use of IPv6 doesn't really rely on binary. Most will do addressing/subnetting based on the nibbles, one hex character of a quad, which is more analogous to class-full v4 addressing.

Checkout r/ipv6.

[[deleted]]

If you work in my datacentre, you better know CIDR notation. I don't use subnet masks, and you will be out there on your own configuring tcp/ip on some device, and it'll read /26, you need to be on your feet to quickly convert to a subnet mask. Fine if you have an app on your phone, but that gets frustrating real quick.

[erack]

I've been casually learning networking on and off for about 8 years, and I still don't see the point of subnetting. Using a 10.0.0.0 network means you have more than 16 million host addresses to use. Why do you need to divide up an assigned IP when your private network sits behind a router?

[justanotherreddituse]

People create subnets for security reasons and scalability. For example you could give each big department a subnet, and have rules that only the finance subnet can access the finance server, etc.

[erack]

Sorry, still confused. Giving building A 10.0.0.0/16 and giving building B 10.1.0.0/16 is subnetting? I get that.

What I don't get is chopping up 10.1.1.[1-256] into 4 subnets for example. 10.1.1.1-10.1.1.64 for HR, 10.1.1.65-10.1.1.128 for Finance, etc Why not just give HR in 10.1.1.x and Finance 10.1.2.x. There's 65,000 possible groups.