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I don't understand Networking


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#1 DefaultGateway

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Posted 18 June 2016 - 12:35 PM

Dear BC Members and Staff,

I want to ask some questions about Networking, because I am not good at it. :(

 

QUESTION 1

Every website has an IP Address.

So instead of typing www.google.com, I could also type in the IP Address of Google, and then I will get to the website of Google.

To know what the IP is of Google, I open CMD and type "ping google.com", then IP of Google is visible.

And then I type that IP in the Browser, and I will go to Google.

But this does not work with every website??

 

QUESTION 2

Everyone has a public IP Address.

If I type my own public IP in the Browser, where will I get to?

I think I know the answer to this one, but I want to hear from you guys to verify if I am correct.

 

QUESTION 3

It's possible to give your own PC a static IP.

What if I put my own public IP as static IP of my PC?

Or what if I just randomly put any public IP as static IP of my PC?

 

QUESTION 4

It's possible to apply an IP Address on a Router Interface.

What if I apply a public IP Address on it?

Because normally you would use Local IP Addresses.

 

QUESTION 5

A website has a public IP Address of X.X.X.X.

What if I use that address as configuration of Static IP for my own PC?

Will the owner of this website get a notification that there is an IP Conflict or something else??

Will that site become unavailable??

 

QUESTION 6

What happens if I enter my School IP in the Browser??

 

I don't know if these Questions are allowed to ask.

In case someone thinks I want to hack something or damage something, then your thoughts are wrong, because I only want to UNDERSTAND and LEARN about Networking.



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#2 DefaultGateway

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Posted 18 June 2016 - 12:44 PM

Just want to add:

 

If you don't know the answers to my questions, please DON'T try it out.

I am afraid that some websites or someone PC can be damaged!

 

@CCNA/CCNP Qualified: Or is this not possible?



#3 Trikein

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Posted 18 June 2016 - 01:05 PM

1. What your describing is called Domain Name System(DNS). It's like 411 for the internet. Website name (domain) is like the persons name and the IP is like the phone number.It will work on most sites, except ones that use shared/virtual hosting. The IP points to a machine that has several websites on it so just typing in the IP doesn't tell the server what website you want.

 

2. Depends on what IP you mean. Excluding IPv6, you get 1 public IP(68.1.2.3) from your ISP and your router creates many private IP address(192.168.x.x) to connect to it. If you went to a friends house and typed in your IP, probably nothing would happen. That IP is assigned to the MAC address of what ever you have plugged into your modem, which is usually a router. If the router is enabled for remote support and typed in 68.1.2.3 , then you will get the login screen for your router. This is assuming you didn't have any port forwarding to direct port 80 to somewhere else.

 

3. Depends on how your ISP works. If they assign non static(DHCP) IPs then the IP will only work until it is assigned to someone else. Also, this would only work if the PC is connected direct to the modem. Putting a random IP is a bad idea, since you could be messing up someone else connection and get bad people to connect to you by accident. 

 

4. Do you mean using a public IP scheme for your private network? Not sure actually. I would NOT suggest doing it, and I think it would break the connection, but not sure exactly how. Would cause routing problems though, that's for sure. 

 

5. Depends on the website. I don't think you will be able to assign yourself a IP that isn't in the routing tables for the ISP. Basically if you can't ping the gateway of the static IP from where you are, you can't use that static IP and most websites won't be on residential connections. If someone in your area was using a static IP for a website, and you configured your router with it, it would break their websites and possibly some of your set up depending. They wouldn't get a notice(unless they pay someone to watch their website), but they would see their website go down and the first thing they would do is ping/tracert it and see it going to you. They would then contact the ISP and you might even get a warning or something. It's against the Terms of Service of most ISPs' I have used. 

 

6. Public or private? At school or at home? If at home and private, probably nothing. If home and public, probably a slash screen for your school's VPN, but that depends how they have their network set up and what they have running on it. 

 

If you are looking to learn, look up DNS, IP scheme, NAT, and OSI model; that should get you started. Do you prefer text, video, examples, etc when learning? I can make some suggestions but the best way to learn IMO is to buy a old router and just play with it.


Edited by Trikein, 18 June 2016 - 01:09 PM.


#4 DefaultGateway

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Posted 19 June 2016 - 02:02 AM

Thank you very much for your Answers. :)

And don't worry, I am NOT messing with IP Addresses.

I just wanted to know how some things worked.

 

There is one last question I would like to ask.

In some Cisco Assignments they let you assign a 209.165.X.X. address to a Loopback Interface and your own PC.

Is this OK?? (because 209.165.X.X is a public address)


Edited by DefaultGateway, 19 June 2016 - 02:05 AM.


#5 technonymous

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Posted 19 June 2016 - 05:37 AM

Thank you very much for your Answers. :)

And don't worry, I am NOT messing with IP Addresses.

I just wanted to know how some things worked.

 

There is one last question I would like to ask.

In some Cisco Assignments they let you assign a 209.165.X.X. address to a Loopback Interface and your own PC.

Is this OK?? (because 209.165.X.X is a public address)

That is a tough question to answer. I am in no way a network engineer guru. With that said, Yes, in a sense it is a public IP a ISP would assign... However, you can setup that IP on a private network too. If we're talking about large ISP networks here.. Then, generally working with commercial grade routers you would create loopback interface for the router itself and assign an IP.

 

In addition, this opens up the ability to take advantage of all sorts of protocols IE: Border Gateway Protocol, peering, data metric path vectoring, transit services (leasing of bandwidth) etc for internet routing. This way neighboring routers can talk to one another and share routing table information while enforcing their security protocol policies of their own. Large networks are all connected like a spider web eventually. Hence the "WWW". However, a router in the US may have a neighbor in the EU and ultimately connected by a fiber line under the ocean. Who knows!


Edited by technonymous, 19 June 2016 - 05:46 AM.


#6 DefaultGateway

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Posted 19 June 2016 - 06:36 AM

Thank you for your Reply. :)

I have no questions anymore.

 

Cheers,

DefaultGateway



#7 Kilroy

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Posted 19 June 2016 - 09:50 AM


QUESTION 1

Every website has an IP Address.

So instead of typing www.google.com, I could also type in the IP Address of Google, and then I will get to the website of Google.

To know what the IP is of Google, I open CMD and type "ping google.com", then IP of Google is visible.

And then I type that IP in the Browser, and I will go to Google.

But this does not work with every website??

The IP address to name conversion is handled by DNS (Domain Name Service)

Pinging a web address will give you one IP address, provided the web site is configured to respond to ping attempts. Machines can be configured to not respond to ping requests. There used to be an attack called Ping of Death that could take a web site down with improper ping requests.

One server can actually handle many different functions, Web Server, FTP Server, Mail Server, Image Server, and so on.

 

 


QUESTION 2

Everyone has a public IP Address.

If I type my own public IP in the Browser, where will I get to?

I think I know the answer to this one, but I want to hear from you guys to verify if I am correct.

Not necessarily true. Some ISPs (Internet Service Provider) give their users private IP addresses (10.x.x.x or 192.168.x.x). This is due to running out of public IPv4 addresses.

If you type in your public IP address, which you can find by going to WhatIsMyIP.com most likely you will get nothing. Your firewall and router will need to be configured to allow the traffic and the traffic must be allowed by your ISP. Many ISPs block mail server and web server traffic. In order to receive something the proper ports must be opened and a device must be listening. Any machine that is listening on your public IP address can be attacked from anyone on the Internet from that port. Shodan.io can show you many devices on the Internet.

 

 


QUESTION 3

It's possible to give

your own PC a static IP.

What if I put my own public IP as static IP of my PC?

Or what if I just randomly put any public IP as static IP of my PC?

 

Yes, you can give your own PC a static IP address. This is frequently done on networks for devices that are on all of the time, servers, network printers, video cameras, etc.

 

In order to set your PC to your public IP it would need to be directly connected to the Internet and not behind a router, HIGHLY NOT RECOMMENDED. How long this would work would depend on your ISP. Most ISPs charge to have a static public IP address. So, while you may be able to operate for a while with a static IP address your ISP may change your address and your machine would stop working.

 

 


QUESTION 4

It's possible to apply an IP Address on a Router Interface.

What if I apply a public IP Address on it?

Because normally you would use Local IP Addresses.

 

Yes, that's how your router works. The WAN (Wide Area Network) side has your public IP address and the LAN (Local Area Network) has your private IP address. You can't use the public IP address on both sides of the router. Imagine your router needed to route traffic to the WAN from the same address on the LAN, since both are the same how would it know where to send the traffic?

 

 


QUESTION 5

A website has a public

IP Address of X.X.X.X.

What if I use that address as configuration of Static IP for my own PC?

Will the owner of this website get a notification that there is an IP Conflict or something else??

Will that site become unavailable??

[/quote]

Nothing would happen, other than your PC would have no Internet access. In order to cause any issue your ISP would also have to be the ISP of the web site. Take a read or listen to [url=https://www.grc.com/sn/past/2006.htm#25]Security Now! Episode 25 - How the Internet Works - Part 1[url] and [url=https://www.grc.com/sn/past/2006.htm#26]Security Now! Episode 26 - How the Internet Works - Part 2[url] for more information on Internet Routing Tables.

 

[quote name="DefaultGateway"]

QUESTION 6

What happens if I enter my School IP in the Browser??

The answer is the same as question 2, it all depends on what devices are listening on that IP address.


Edited by Kilroy, 19 June 2016 - 09:53 AM.


#8 DefaultGateway

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Posted 19 June 2016 - 10:28 AM

I have never heard from the site "shodan.io".

Thank you for sharing this. :)

 

 

Some ISPs (Internet Service Provider) give their users private IP addresses (10.x.x.x or 192.168.x.x). This is due to running out of public IPv4 addresses.

 

Do you mean IPv6?



#9 Trikein

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Posted 19 June 2016 - 12:49 PM

@BC Advisor How common is Carrier NAT in the US? I know it's more common in Europe and Asia but I thought most large ISP in the US has a stock of IPv4.

 

Also, anyone know of any performance benefits for a consumer with IPv6 vs IPv4? I know you don't need NAT, but is UPnP still used? Does a IPv6 firewall work inherently different? 



#10 Kilroy

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Posted 22 June 2016 - 02:29 PM



 


Some ISPs (Internet Service Provider) give their users private IP addresses (10.x.x.x or 192.168.x.x). This is due to running out of public IPv4 addresses.

 

Do you mean IPv6?

 

No, I mean IPv4 addresses.  There are sufficient IPv6 addresses to give everyone who has ever lived their own address.  Home users have used NAT because our ISP only gives us one one IP address.  I've got 16 devices that connect to my home network for just myself and my spouse (most of them are mine).  Once all of the IPv4 addresses were allocated the ISPs have had to find ways to provide addresses for their users.

 

I don't know that I'd want to go IPv6 for home, mainly for security reasons.  If you're using a public IPv6 address you are directly connected to the Internet meaning that you can be directly attacked.  I'd much rather have all of my equipment sit behind my router.  With the number of possible IPv6 addresses I don't know how likely an attack is, but I'd rather not take any chances until we see the issues.



#11 technonymous

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Posted 23 June 2016 - 07:16 AM

I don't see how they can try to hack you directly since the ipv6 IP that you're assigned is coming from the router. I notice when I go to websites to check IPV6 it lists my pc's IPv6. However, the first octets of the IPv6 are that of the routers as well. So there is still a sort of NAT forwarding protection going on there. If no session or forwarding port is open on the pc then the packet is going to get dropped by the router.






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