Community archive

Ask something
Discussion Locked

Few Simple Netowrk Questions

0 helpful
34 replies

by isaaclau

Closed to new repliesThis discussion is closed. It stays readable, but it takes no new replies.

1. Routers are used to connected mutiply network , right? How about switch? Can it also connect mutiply network just by using the UPLINK connections?

So what are the difference in the usage of switch and router? (I know that they are base on layer2 and layer3, in which router has path determination..but so what? )

2. Can I said router is a gateway? Why do we need a gateway?

3. ppl todays mostly using routers to share Broadband to the Internet? Why can't a hub of switch in doing so?

------------------------------
I am now learning CCNA semeaster 1, but just got those silly questions. It would be great if you can help me. Thx a lot!

34 replies

by isaaclau

For question 3:

"why can't a hub OF switch in doing so"
is changed to "why can't a hub OR switch in doing so"...

sorry

by tech4life

http://www.darron.net/network/secondpage.html

"Switches control the flow of network traffic based on the address information in each packet. A switch learns which devices are connected to its ports (by monitoring the packets it receives), and then forwards on packets to the appropriate port only. This allows simultaneous communication across the switch, improving bandwidth.

The term ?hub? is sometimes used to refer to any piece of network equipment that connects PCs together, but it actually refers to a multi-port repeater. This type of device simply passes on (repeats) all the information it receives, so that all devices connected to its ports receive that information."

tech4life

by isaaclau

Thx first, I know the difference between hun and switch.....my real problem is concerning router..gateway and switch.........

pls see my question again.......

really thx!

by lordinfidel

These are the basic concepts of routers.

1. Routers are also known as gateways. There is a difference but it is only in the way they are deployed, they both do the same thing, it is only the verbage in which they are acting.

A router can connect dissimilar networks together. They can be dissimilar based on protocol used or more commonly on todays net, different IP networks. Which is where the term routing comes in to play. A router routes requests from 1 netwk to the other.

Routers are used thoughout the Net (ISP backbones) to get your request from point a->b->c->d->destination.

A gateway *is* a router. It is basically your computers exit point from your network. Which is why it is called a gateway. But for all intesive purposes it is still a router. It is routing your request from your local net to another netwk that your computer can not get to without it's routing you to it.

by isaaclau

quote"A router can connect dissimilar networks together. They can be dissimilar based on protocol used or more commonly on todays net, different IP networks"

This sentence is in particular make me undersatnd........
"different IP networks?" doesit mean different Network Number" ???
for example.....
network 203.185.65.0 can't connect to network200.123.45.0 by joinging them with 2 dirrerent switch....instead...router can join them and let them communicate?

Pls help me!

by lordinfidel

You have come to a quandry. How does a host on the 203.285.65.0 net talk to a host on the 200.123.45.0 net?

This is where subnetting and routing come into play.

I am going to take this to a simple step for you.
We are going to use the pvt address range of 10.1.0.0/16 and 10.2.0.0/16 (the 16 stands for a subnet mask of the first 16 bits; eact octet'.' is 8 bits in length)

10.1.0.0/16 will be NetA
10.2.0.0/16 will be NetB

While both address' look the same, they really are not. They are both 2 totally different networks.

Now lets say that you have a 10 port switch or hub, 8 computers (4 are configured for NetA and the other 4 for NetB). And you plug all 8 hosts into the switch.

You would think that because that since they are all plugged into the same switch that they could talk to each other. The numbers are close to each other right?

Wrong. In IP there is no grey areas. You are either part of that network or you are not. NetA is it's own soverign nation and NetB the same.

In order for NetA to talk to NetB, they need to form a "treaty". That treay comes in the form of a router.

So you get a router (or build one, all you need is a machine 'windows srvr, linux' with 2 nics in it)

You assign Nic1 an IP address from NetA
You assign Nic2 an IP address from NetB

Not done yet.

You now need to tell your "router" that it needs to forward ip packets. This is called IP forwarding, with out it your router will be useless.

There is someother tweaking, but I won't get into it here.

Once your system is set up you can now plug that router into your switch.

Then, you would need to go to each of the 8 computers and set up their dflt gtwy. NetA would be set to Nic1's IP, NetB would be set to Nic2's IP.

Now all of the systems will be able to magically talk to each other.

by lordinfidel

So you see, switches know nothing about routing IP. They only know about MAC address. And they can only send packets to the ports(plugs on the switch) it has locally that it can relate a MAC to.

They can not 'route' MAC address'. In fact a MACaddress is not routable. IP is a routable protocol. IPX is also routable but it is not used on the NET. IP is the de facto standard for the net which is why I keep using it in the examples.

(When I say MAC, I don't mean a macintosh, If you tryto make a mac a router it would probably burst into flames)

Now your 2 address', in order for those 2 nets to talk to each other directly, there must be a router that is connected directly to both netwks.

If not, then that is where routing comes in. Which is how the net works. You need to get to a website (or any other remote service), located on a netwk that is not connected to yours. Routers in between you and the remote net, route your request to the destination net and back again. (not necessarily taking the same path back).

Essentially, there are a few basic concepts. Once you understand those concepts, you can build on them.

by lordinfidel

As we saw before, a router routes requests between dissimilar IP networks (can be other's like protocol, I am just sticking with IP for this example).

A switch on the other hand does no IP routing. If you plug 2 hosts from 2 different networks into a switch, they will not be able to talk to each other unless a router is present. The switch knows nothing about convential IP routing.

What makes a switch special, is that it keeps a arp table of all of the hosts connected to it.

This makes a switch different from a hub. When you plug into a switch, the switch records your MAC address into it's arp table. It now knows what port you are plugged into. When a request for your system is received via ARP, and it hits the switch you areplugged into, the switch knows what port to deliver the request to.

Unlike a hub that does not keep that information. A hub will have to ask each port every time it receives a request to see who the owner of the MAC is.

There are some other perks of switches such as portfast, spanning tree and remote mgmt of the ports. Which makes switches the preferred connection devices in production networks and ISP's.

Hubs are fine for local lans and for non-mission critical netwk segments.

by lordinfidel

I hope that you can now tell the difference between a router and a switch.

And why you don't use switches to connect to the net and why you need a router(gtwy) to do so.

Now for my soap box
------------------
(this is for anyone reading)

I understand the need for people to want to go to school and learn networking. It is a very lucrative career path. But there are certain steps that need to be followed when going after mid-high level certs such as the CCNA, MCSEand RHCE.

A certain knowledge of computing should exist before attempting these certs.

I for one worked in the industry first before even thinking about taking my exams.
By the time I though I was ready for the CCNA, I was already versed in routing.

My point is, certs today have become more of a training ground for people instead of what they were originally designed for. An assesment of ones present skills relating to that track.

Not learning it as you guy. Before taking the CCNA you should already be familiar with routing concepts. Before taking the MCSE you should be able to install the OS in your sleep. The RHCE you should know linux, used linux, configured linux, loved linux, before even thinking about taking the exam.

The certs should not be, "hey I think I want to be a CCNA, lets take a course"

On a side note, All of my peers who have their certs have never taken a class. Myself included. Our feeling is that there is little a school can teach you that you can't teach yourself.

And that my friends is the crux of good computing, being able to teach yourself. Without that skill, you should not even consider computing.

by admin

Not the beginning of a journey, but a marker on the path :)

It seems to me that it is way to difficult for most people to retain very much until after they do it until, as you say, they can do it in their sleep. Then again, the job market is pretty bad around here. I noticed that nothing IT related even made the top ten list of occupations to consider at the local State University this year and possibly this will be a good thing in time and four years of school might wait out the difficult time getting that first experience, and certainly won't make matters worse for the person that loves IT.

by mrjay67

I couldnt agree much more with your soapbox comments. It seems that too many people are taking these classes/exams and have no knowledge of the real world of IT. I personally have yet to actually take any tests. I have seen too many people that have certs that ask me simple(newbie) questions. It's appauling that i have to compete with people such as that. There are few enough jobs out there(at least in my local)as it is, and then we have to compete with people that are as i call them "paper MCSEs or CCNEs". I have seen that there are real answers and then there are Microsofts. With so much theory in many of the cert exams i dont see how the paper certs are able to get by in the real world. Perhaps eventually this will weed out those in it for just the "money" where ever that went. Sorry but your soapbox hit a nerve with me.

PS. im not saying ALL NEW MCSEs dont know real world or are lacking in some way. It just seems to be more common than should be.

Just my thoughts.

by djent

Now all you have to do is educate the HR people along with the paper tigers.

by rmet

I have been in "the" industry since the late 70's. I moved into networking in the late 90's. Granted with my experience I am no wiz kid, but I do have a solid foundation of the BIG picture. I got my CNE, and of course am blackmailed to continue witheach new version. If you do not get the newest cert, then you lose them all. As much as any other reason, that is the main reason people are chasing certs. I worked with 3 and 4, and have 5, but no experience with 5. Companies do not know how to read resumes, nor know how to relate to honesty. We are on a rocky road!

by bertzz

A Hub works in the link layer of the OSI model, that is it only repeats packets as if all the computers were attached to the same wire. I does not route packets between different networks.

A Switcher also works in the link layer of the OSI model,but includes a little level of intelligence, only repeat to the port where the destination computer is plugged.

A Router works in the network layer of the OSI model, that is, a router can route messages between different networks based on the routing tables or learning protocols.

A Gateway works up to the seventh layer of the OSI model (application layer), different types of gateways can translate different wire protocols and standars, can translate between FTAM and FTP, between X400 and SMTP, between token-rings networks and ethernet networks, and so on.

Recommended readings: the Open Standard Interconexion model of the International Standard Organization.

Regards.

by lordinfidel

I was just reading your post.....

Not for nothing, but You really need to read the doc that you quoted. I don't mean to blast but.....

A Gateway works up to the seventh layer of the OSI model (application layer), different...

R U High? A gateway is a *ROUTER*. It has nothing to do with layer 7. Layer 7 is an application level (ie mail server, ftp, web).

Read your OSI model.

Routers are Layer 3 devices. All they know is IP. (or whatever protocol they are configured for)

Do not confuse a Mail Gateway with a Router. They are 2 *VERY* seperate things! A mail gateway can not route packets. It works at the app layer and passes the message down to the lower layers.

FYI- it's not called a switcher, it's just a switch. This is not baseball.

by bertzz

Excuse me, but a gateway is NOT a router. You can call it so if you like, but it isn't. Please read the OSI model again, I have it in my hands.

by lordinfidel

Now that I have had time to sleep, let's go over what we have learned.

We have learned that a Gateway can be several different types of devices. The term is interchangeable between it's given use.

But the base concept remains the same. It connects 2 or more systems that normally are not connected and allows them to communicate.

As for the debate....

All I can give on that is some advice. When you debate, make sure that you are correct and that you have good, well-known, legitimate third party sources to pull from.

It is one thing to pull a quoute off of known-name news site that is off of some-ones web page that they put up. It's another to go to abc/nbc to get the article.

Know your sources, but always check out theother debaters source, regardless of it's location.

I do hope that other have gotten something out of this debate and that it has not gone to waste.

by lordinfidel

A gateway (in the networking world) is by definition, From RFC2328 STD 54

http://www.faqs.org/rfcs/std/std54.html

Section 1.2.

Definitions of commonly used terms

Router

A level three Internet Protocol packet switch. Formerly called a gateway in much of the IP literature.

----------------------

Here are some other terms.....

IGP
BGP
EIGP
EGP

What do you think the G stands for.

----------------------------------

If a router is not a gateway then I need to resign my hob and give back my CCNA and RHCE certs!

I guess we should notify the IETF of the misuse of the term "Gateway" Also".

by lordinfidel

EIGP is a mistake. (aka typo (accidental mix)

And IGP is wrong
What I meant to type was IGRP

I think I was trying to correct the first one and type the second one, but still messing up.

IGRP is the Interior Gateway Routing Protocol
EGP is the Exterior Gateway Protocol
BGP is Border Gateway Protocol

I apologize for the confusion that this may have caused some of the readers.

For further information about these you can go to www.protocols.com

Protocols.com will give you a brief explanation of each plus a link to the RFC which governs that protocol.

by lordinfidel

I made a mistake im my refrernces to the routing protocols.

The list should be

IGRP- Interior Gateway Routing Protocol
(there is also the E-IGRP, extentded .......

EGP- Exterior Gateway Protocol
BGP- Border Gateway Protocol

I apologizefor the mis-typing of the list.
In any event, these are commonly used protocols used on routers.

For further definition of these routing protocols you can go to www.protocols.com

You can find links to the current rfc's covering these.

by lordinfidel

The modern OSI model is broken up into 4 layers.

It loosely translates to the classic 7 layer model.

From Page 9 of TCP/IP Network Adminsitration.

Layer 1= Network Access Layer
Layer 2= Internet Layer
Layer 3= Host to Host transport layer
Layer 4= Application Layer

I live, breath, eat and sleep routing. But apparently I must have missed something in Routing 101. Or maybe it was because I have *NEVER* attended a IT school in my life.

I guess I need to enroll in a boot camp because I am obviously an Idiot. Maybe I should remove my routing protocols from my routers and install them on my Mail server, or better yet my web servers.

Oh and call MS, because they need to change all of their OS's tcp/ip properties pages to read Default Router and not Default Gateway.

And don't forget to call Linus Torvalds. He needs to get with his open source people and change all of the Distros so that the route command is displays router instead of gateway.

I forgot Cisco... How can I forget them to. I guess we need to revoke all of the CCIE's out there who answered the question incorretlty when specifying their default gateway!

by lordinfidel

Ya know, you try to be nice and share your knowledge, and then you get people like that who are just plain ignorant.

And I have now been up for 48 hours. So my tolerance level for stupidity is really f'n low.

by lordinfidel

http://www.thelinuxreview.com/howto/intro_to_networking/c5736.htm

Often, the router that is used to connect a LAN to the Internet will be called a gateway. It will have added capability to direct and filter higher layer protocols (layer 4 and up) to specific devices (such as web servers, ftp servers and e-mail servers).

Gateway's OSI Operating Layer

A Gateway operates at the Transport Layer and above and it typically translates each source layer protocol into the appropriatedestination layer protocol. A mainframe gateway may translate all OSI Model layers. For example, IBM's SNA (System Network Architecture) does not readily conform to the OSI Model, and requires a gateway to translate between the two architectures.

I think I have made my point.

Have you even read my profile? Do you notice that no one even dares get involved with this?

Have you ever read any of my other posts?

I do complex routing all day. Security audits; I can hack into systems easily. I participate in TR, not as a novice, but to share my insights with others. There may be times that I learn something new, that will always be present in the career of an IT pro.

But today is not the case.

There is no amount ofconvincing that you can give me or the IT communinty that a router is not a gateway.

They are one and the same.

There are however different types of gateways, as the term can be used across platforms. The most popular being a mail gateway. Aproxy can also be considered a gateway.

by lordinfidel

A gateway by definition is: (from dictionary.com)

1.An opening or a structure framing an opening, such as an arch, that may be closed by a gate.

2.Something that serves as an entrance or a means of access: a gateway to success; the gateway tothe West.

3.Software or hardware that enables communication between computer networks that use different communications protocols. Also called router2

By this definition, (2)means to access- anything that serves as a entrance to a differentlocation can be called a gateway.

Routers are gateways to a different netwk. Mail servers (gateways) route mail to different domains. Proxy's receive requests from one network and pass them thru to it's gateway. A proxy is a intermediary gateway, but still a gateway.

I beleive my point has been driven home. If you still can't figure this out, then I suggest you go work for AOL tech support.

by lordinfidel

Match up with someone who is my equal.

I feel bad sometimes (well not really) when I trample on people just starting out. But I usually try to do it with guidance, give them hope or an answer, point out why they are wrong and show them how to correct it.

This is not the case. No one calls me a Novice and get's away with it. It's open season in hunting country.

DoubleKill-GodLike

by isaaclau

Routers are used to connect dirrerent network(network/subnet address), while switch can't do it.......just becoz it is layer 2.....not Ip(network Layer), is that correct????

Take your example......but for the 8 computers connecting to one switch.....although there network number aren't the same........but they are both connect to one switch........and switch basically just use MAC address???? Why can't they communicate????? Sorry.....I am really just a newbie...

Second...I've seen some post complaining the current IT ppl doesn't really know the real World of IT........I would like to claim that I was actually 16 yrs old....I was interest in networking so that I start to learn networking....I was a programmer....but like to learn more about networking......only!!!!

by lordinfidel

question 1- again it all has to do with routing.
The 2 sets of systems are on different subnets and need an intermediary device (router) to route the packets between the 2 networks.

A swtich does not have this capability.

#2- As far as your age, that's fine. I for one am not going to blast you for attempting to learn. That's what forums like this are for.

It allows the newbie to interact with the more seasoned. Something that someone just starting out won't be able to do.

If I started when I was 16 I would be a routing god by now. So stick with it, you have a long way to go. Don't expect to learn everything in one day. When someone blasts you just remind them that you are not in an admin role and are just learning by doing. Most IT pro's respect those who attempt to learn the info on their own and ask questions then those who are going to a school.

Just hang in there

by isaaclau

For Transport layer: It controls the traffic flow,
if there is an error in transmission, then it provides a re-trnamission. Also....(Qos) is talked in here. How much data should be sent once time to ensure better traffic..........

For Network Layer.....It concerns only the path selection by looking up at the destination address(Netowrk Number)...then it will choose the best path to go in accordance with the router.....It use a "Best-Effort" delievery only....no one make sure if packet willarrive there.....the flow of traffic is not being concerned in here....

Is that Correct????

Second, I was happy that you don't mind I asking such silly question......and give me the clear explanation. this really encourage me to learn Networking......I study networking not just like others , who thinks just have some lessons , will have good carrer path....I am interested in this subject....and planning to spend lots of time.......that what you called "real World, real IT"............

This discussion is closed to new replies.