Need some advice on learning networking

[BillyCarpenter]

Re: Need some advice on learning networking

By the way, I really didn't go very deep on RIP. Here's something interesting. Maybe I can explain it where it'll makes sense.


When there are multiple routers in a given network and RIP is deployed on all of them, it makes the routers "talk" to each other and share information. They let each other know about "routes" that they are directedly connected to and thus the other routers can add those routes to their routing table. That's why it's sometimes called: ROUTING BY RUMOR.

[blackcat4866]

Re: Need some advice on learning networking

It would be a huge time commitment, but I think you're the type of person that would be great at networking. Just judging by your work ethic/habits, this would be right up your alley.

Perhaps, but I would need to apply it to something frequently to retain any of it. True, I learn things quickly ... and forget them just as quickly if it's not used. I seem to retain only the barest outline of a topic, then dig back into the database for the details. =^..^=

[BillyCarpenter]

Re: Need some advice on learning networking

Perhaps, but I would need to apply it to something frequently to retain any of it. True, I learn things quickly ... and forget them just as quickly if it's not used. I seem to retain only the barest outline of a topic, then dig back into the database for the details. =^..^=

I hear ya. After being away from copiers for about 20-years, I had forgotten so much and plus things had changed since then. That's why I'm never gonna be an elite copier tech again. For starters, I don't have access to the training schools or information and I don't work for a big company anymore so I'm not seeing the volume of service calls that I once did. That stuff matters. Luckily, I was able to get enough information from you and others on this site to get it figured out but I'd love to have the proper training once again.

I still think you should consider taking the same CCNA course that I'm taking. It's only $15 per month and it's pretty good.

[BillyCarpenter]

Re: Need some advice on learning networking

I have nothing to do tomorrow so I'm gonna go for as long as I can tonight on CCNA.

These routers continue to reveal their secrets.


I told you about the 4 routing protocols. Normally, in a production enviroment only ONE routing protocol is used. Using more than 1 is considered bad practice. However, sometimes it's unavoidable. For instance, 2 companies may merge and each is using a different routing protocol. I know what you're thinking....how do we make it work when using 2 routing protocols? I'm glad that you asked.


A router uses what's called a "metric" when choosing the best route. That's true for all routing protocols. The lower the metric number the better as far as the router is concerned.

RIP may have a metric of 60 and OSPF may have a metric of 90 for the same route. So, what route wins? If you said the metric with the lowest number, you'd be mistaken. And here's why.

OSPF and RIP derive their metric in totally different ways so its pointless to compare them.

Fortunately there's a another way to help sort all of this out.


There's something called ADMINISTRATIVE DISTANCE.

The Administrative Distance is a measure of how trusted the routing protocol is. If routes to the same destination are received via different routing protocols (RIP/OSPF) the protocol with the lowest Administrative Distance wins.


Here's the Chart:


Connected Interface: 0
Static Route: 1
External BGP 20
EIGRP 90
OSPF 110
IS-IS 115
RIP 120

Since rip has the highest Administrative Distance, it's routes will be completely ignored and OSPF will be used.

Whew!!!

[BillyCarpenter]

Re: Need some advice on learning networking

For the better part of the day I've been configuring and verifying RIP in the virtual lab. It's interesting to take the "theory" and apply to the actual routers/switches/PC's.

The latest lab topology is the most complex and comprehensive yet. You can take a look at the topology below:


RIP.jpg


This was a lot to configure and verify. The train has officially left the networking station.

I'll explain more about the configuration in a later post but right now I want to talk about "subnetting."

I've talked about subnetting numerous time but it bears repeating: If you do not master the art of subnetting and understand it thoroughly, you don't stand a snowball's chance in hell of being able to network in a production environment. A subnetting calculator isn't gonna help you read a routing table that has been automatically summarized by the routing protocol. If you don't understand subnetting, you'll be left dazed and confused. Take my word for it.

[BillyCarpenter]

Re: Need some advice on learning networking

Hopefully, you can better see the network topology that I'm working with.

Here's what I had to configure and verify.


See Network Topology:


rip2.JPG

Here's what I had to configure and verify:

1. Set up RIP on all 4 routers and ensure that the it's enabled for all the correct networks on each router. (Note: Know your subnetting !!!)
2. Once RIP is set up on all routers, verify that all ip routes from the other routers are populated on ALL the routers.
3. Make sure we can ping all the networks.
4. Set up a default route to the internet. (Gateway of last resort.) I could have configured a gateway of last resort on each of the 4 individual routers but this is considered bad practice. The correct way of doing it is to configure a gateway of last resort on the core router (this is the router that the other 3 routers connect to.) and then advertise it via RIP.
5.Configure all of the routers to use the correct DNS Server.
6. From the routers, make sure that we can ping the facebook.com server by IP address and by hostname.
7. Configure each router on the 3 networks as DHCP servers and make sure all 9 PC received DHCP addresses. (Yes, Cisco Router can be set up as a DHCP Server.)
8. Log on to each PC and make sure that we can can ping Cisco.com (hostname and IP address)
9. Configure Loopback addresses for all the routers and switches. (A loopback is a virtual IP address that's used for testing purposes). It comes in very handy because unlike physical connections, it never goes down.

This lab kinda caught me off guard because it covered everything I've learned thus far about Dynamic protocols but they threw in some stuff that we covered way back. I had to think about it for a minute.

[BillyCarpenter]

Re: Need some advice on learning networking





Advertise default routes using RIP

NOTE
RIP is not explicitly listed in the latest 200-301 version of the CCNA exam topics (whereas OSPF is) but you can still be tested on it in the exam.

Consider the following example network:




default-information originatee is a candidate to be the default route.

[rthonpm]

Re: Need some advice on learning networking

You're just showing why for most of this I generally sub out infrastructure work. Except for DHCP, which we do with Windows Servers.

Consider also how once these things are set up just how fast they work. I did a DHCP server a few weeks ago with eight VLAN's and a pile of reservations. When the server actually went into production, everything was all but instantaneous as soon as hosts connected to it.

Sent from my BlackBerry using Tapatalk

[BillyCarpenter]

Re: Need some advice on learning networking

You're just showing why for most of this I generally sub out infrastructure work. Except for DHCP, which we do with Windows Servers.

Consider also how once these things are set up just how fast they work. I did a DHCP server a few weeks ago with eight VLAN's and a pile of reservations. When the server actually went into production, everything was all but instantaneous as soon as hosts connected to it.

Sent from my BlackBerry using Tapatalk

Configuring routers and switches is a totally different technology and skillset compared to Windows Server. That becomes readily apparent once you apply it to a production environment. Unless a person has that training with routers & switches, I think most would have no choice but to sub it out. That same can be said for Windows Servers. Unless a person knows what they're doing, they would have to sub that out.


As far as DHCP? Routers generally aren't used for DHCP Servers. I'm still in the training stage and they want to make sure that we're aware that it can be done and that we know how to do it. And it's instantaneous in this case too. The hosts receive a DHCP address in the blink of an eye.

[BillyCarpenter]

Re: Need some advice on learning networking

Just when I thought I was done with RIP, I get pulled back in. This time it's about classful vs. classless routing.

"Classless" implies that routing decisions are not tied to the class of the IP address: Class A, B, or C, but may be based on any portion of the 32-bit IP address as specified by the mask.


I know that doesn't make a lot of sense. I'll attempt to explain it.

Lets say that I enter the following route in the router: 10.1.0.1/24. That means that the first 3-octets are the network portion of the IP address and the 4th octet is the host portion.

Here's the potential problem with a router that using a "classful" routing protocol.

IP address 10.1.0.1 is a Class A Network. The first octet always identifies what class of network it is....regardless of the mask. So, a "classful" routing protocol doesn't care about the the /24 cidr and it's gonna advertise my route as a class A network (10.0.0.0/8). That's not good.

That sounds complicated, I know. And I probably butchered the explanation. Sorry.

PS - The solution is simple. You can turn "auto-summary off in RIP or use a protocol that doesn't use classful routing....like OSPF. I just have to learn this stuff for the stupid test.

[BillyCarpenter]

Re: Need some advice on learning networking

I was able to spend a lot of time on CCNA over the 3-day weekend. I feel that I made a lot of progress. Things seem to be getting easier. That's not to say that they're easy...just easier than what they were.


I made a concerted effort to really learn the fundaments inside and out and that has paid off in spades for me.

Anyway, here's the bottom line for classless vs. classful routing protocols. They work hand in hand with route summarization. Bottom Line: Route Summarization = good. Auto Route Summarization = bad.

Don't let the routers auto summarize the routes for you. It will come back to bite you. Turn auto summarization to off and manually summarize the routes if called for.

[BillyCarpenter]

Re: Need some advice on learning networking

This section on Dynamic Routing Protocols has been a real doozy. I still have to cover OSPF and then I'm done with this topic as far as what's outlined in the curriculum. However, I don't think this online course alone will be enough to pass the test. I need to read about Dynamic Protocols in the official CCNA book and watch some videos from a 3rd party. And then I need spend several hours in the virtual lab.

I see that "Spanning Tree" is about 3 topic away and I hear it's a real bitch to learn.

[BillyCarpenter]

Re: Need some advice on learning networking

Welp, I was at the very end of Dynamic Routing Protocol section and that's when it happened...they threw me a curve ball. What am I talking about? The learning just went to a much deeper understanding.


Here's an example of what I'm talking about. Before I give an example, here's a question for everyone: What's the difference between a broadcast and multicast signal?

Here's another question: What is the IP address for a broadcast and multicast signal?


Were you able to come up with the answer for those questions?


Answer:

A broadcast signal goes out to every host in the subnet (network) and every host must process the packet.
A multicast signal is a method of sending packets to a group of interested receivers in a single transmission.


What is the IP address for broadcast and multicast?

Answer:

Broadcast address: 255.255.255.255
Multicast address: 224.0. 0.0 to 239.255. 255.255

Why is any of this important?

There's one universal truth in networking that I have noticed. BROADCAST TRAFFIC IS BAD.

One of the benefits of VLANs is that it segments broadcast traffic and frees up resources.

How does this any of this relate to Dynamic Routing Protocols?


The answer is complex and I'll attempt to explain:

In order for a Dynamic Routing Protocol to do it's job, it must update it's routing table frequently if there's any changes. For instance, if the connecting router goes down, the next door router must update it's routing table by deleting these routes? But how do routers update their routing tables? Well, RIP v.1 (version 1) sends out a broadcast signal to everyone on the network asking for an update. RIP v. 2 did away with broadcast requests and used multicast.

If you followed all of that, you're doing great.

[BillyCarpenter]

Re: Need some advice on learning networking

I need to make a small correction. I said that broadcast traffic is bad. It would be more accurate to say that broadcast traffic is a "necessary evil." Without using a broadcast signal, IP networking doesn't fly. But it creates problems.


Also, just to clear up any confusion about multicast signals....

Don't let it confuse you. A multicast is simply a communication between different hosts that have signed up for the same application. In this case it's RIP version 2 that is the application. Netflix and YouTube also use multicast signals.

[BillyCarpenter]

Re: Need some advice on learning networking

PS - All of that information led to learning about configuring a passive interface on a router to cut down on broadcast/multicast traffic. It never ends it seems. I'll explain that later.