Network troubleshooting questions please?

[mikehende]

Hey guys, let me start this new thread to keep things uniformed? I am doing some research on network troubleshooting and have some questions on things I have found on the net please:

1] Can an ip address be different from a Default Gateway address?If yes, what would be the circumstances?

2] If one pc on a network gets banned from an internet site, can another pc on the network work since it will have a different IP address?

3] When an IP address changes by unplugging a router, will it auto change the ip addresses of every pc on the network?

Thanks.

 

[JackMDS]

1) Not clear what is it that you are talking about.

Each Ethernet Capable Device on a Network must have its own unique IP.

Gateway is usually the IP of a Device that provides service (like DHCP) to the Network's Devices. Typically it is the Router's LAN IP on a regular Network. Gateway IP can be any IP provided, it assigned correctly according the specific configuration of the Network.

2) A PC behind a Router can not be Banned from a Site. Sites see your WAN (ISP assigned IP). So basically all the PCs behind the Router are blocked regardless of their local IP.

3) If you talking about ISP external Address it might or might not change depending on the ISP policies

----------------------------
P.S. This type of general questions do not provide any real info about the Network its devices and configuration to give a credible answer.

They just invoke Guessing and indicate some sort of O.P Anxiety following some wrong action.

May one or two of the Books in the right side of this page might help.

https://www.google.com/search?q=networking+for+dummies&ie=UTF-8

 

[mikehende]

Thanks, sorry about first question, that was my mistake. Networking is very difficult for me so please bear with me and let me ask these questions to be sure I get?

1] The gateway IP address is the modem's address?

2] A router has a different IP address from the gateway address?

3] So it's your router's address which site's ban so if you use any pc behind that address then any of those will be blocked too? If yes, then only way to not get blocked is to change your router's address? In this case your router's address is the Default Gateway address?

 

[Pandasaurus]

Short (as possible, in this case) answer...

1) Depending on your exact configuration... Possibly. More on this in a second.
2) Technically, yes. A router will have two addresses.
3) Yes, yes, no.

A router handles traffic traveling between two networks. In this case, between "the internet" (we'll just leave it at that for now) and your own network (home, work, whatever the case may be). Part of this process is what is called "Network Address Translation (NAT)". Your router has a publicly known IP Address. This is the address anyone else on the internet will use to communicate with any device on your network. This address is unique, not used by anyone else in the world (basically). Typically, you will only have one public IP, no matter how many computers you have plugged into the router. The router will keep track of all of your "private" IP Addresses (these are the addresses used by your computer(s). These addresses are not unique in the world, and can be (and are) used on any other private network in the world. However, they are unique within your own private network.), and which traffic from the internet is destined for which private address. The router then "translates" the private addresses into your public address. This is how you can have multiple computers connected to the internet through one router and one public address.

The basic explanation of the "Default Gateway" is... The computers on your network don't know how to communicate with anything outside your own private network. So, any time they need to get "outside", they simply send the traffic to the Default Gateway, which has the responsibility of sending the traffic on its way.

So, the most correct answer to your final set of questions is... The "public" address of your router would be what a site uses to ban you. This has nothing to do with your Default Gateway. Your public address is controlled by your ISP.

And no, I won't tell you how to try to sneak past a ban. We've already had a thread on that this week.

 

[mikehende]

The "public" address of your router would be what a site uses to ban you. This has nothing to do with your Default Gateway. Your public address is controlled by your ISP.

And no, I won't tell you how to try to sneak past a ban. We've already had a thread on that this week.

Thanks, things are a little clearer now but please note the "ban" example was only used here because that was what I had come across in one of the tutorials on the net, it has absolutely nothing to do with myself personally .

I am trying to learn the basics of remote internet troubleshooting, I am being told I would need to know mainly about pinging and specifically how to change an IP address, the latter I am not getting yet but will know exactly what the employer means by this tomorrow morning. My research shows that when you unplug a router it will automatically assign a new IP address, I am not understanding at this time why I would need to change an IP address myself in help desk remote network troubleshooting?

 

[JackMDS]

My research shows that when you unplug a router it will automatically assign a new IP address, I am not understanding at this time why I would need to change an IP address myself in help desk remote network troubleshooting?

Let assume that you are providing remote help service to a Site that every time they power down the Router it get a new WAN IP address (many FIOS location behave this way).

You were connected to the remote via (example) IP. 999.888.777.666

You told them (or did from remote) to power down the Router. When the Routers come back from the reboot the IP changed to 999.888.777.000.

You can Not connect any more unless you know waht the new IP is and change it in your Remote Control client. You might need to call and ask someone to find what the new IP is.

That said if the remote site is configured with a Dyndns.org type of service it is connected to the a sub-domain of the service, then within few minutes you might Auto the connection.

There can be few other scenarios as well.

That what I trying again and again to tell you, your questions are not providing the Technological parameters to give you focused help.

You can expect a 101 course through a forum posting.

These two pages are old and some info there is Gone but theyare depicting the basics of the topic.

http://www.ezlan.net/myip.html

http://www.ezlan.net/vnc.html

 

[mikehende]

I didn't realize it was that much detailed or there would be so many different scenarios

 

[matricks]

My research shows that when you unplug a router it will automatically assign a new IP address, I am not understanding at this time why I would need to change an IP address myself in help desk remote network troubleshooting?

What happens when you restart a router/modem/CPE (customer premises equipment, general term for equipment that connects the customer to the ISP) depends on the ISP. Some ISPs will assign a new address to each session/lease, some will remember the last assigned address for some variable time and assign that same address, and some assign static addresses (customer has one specific IP address tied to him). The goal usually isn't to actually change the IP address, but to obtain a new lease/start a new session (depends on the technology used by the ISP). A new IP address will be a confirmation that this succeeded, but in a customer support scenario you should be able to look up the actual sessions/leases, and not rely on a changed IP address.

About default gateways (and an opportunity to learn about subnet masks): Each network device has an IP address, and also a subnet mask. The subnet mask tells the device which addresses are local, and which are not. Local addresses can be reached directly on the network. If the device wants to connect to an IP address that is not local, it will check its routing table (see "route print" in Windows command line) and figure out if there is a defined route for the network the remote IP address belongs to. If there is a route in the table, the device will follow it. If there isn't, it will go through the default gateway. In other words, if the address is not local, and the device does not know where to go to reach it, it will reach through the default gateway and hope for the best.

If there is no default gateway configured at all, the PC will only be able to reach local addresses, and addresses which have specific routes configured (where the path of routes never relies on a default gateway).

3] When an IP address changes by unplugging a router, will it auto change the ip addresses of every pc on the network?

Not by force. However, all computers using dynamic addresses that lose their connection (detect that the cable connection was lost, or lose wireless connection) will request a new lease when the router is available again. Some routers apply hashing and other techniques to assign the same address to one computer every time, others start from the first address, and hand out addresses in sequential order as requests come in.

 

[mikehende]

Thanks a lot for the explanation guys, I think first of all I am having trouble understanding why a router's IP address change will prevent a pc from accessing the net since whenever my network goes down, I recycle the modem and router and all is fine again, I have never had any other problems with this in the many years I have had internet service and I have never had to do any configuration to the network. I think I will need to purchase the "Networking for dummies" handbook:

http://www.amazon.com/Networking-Du...893683&sr=8-2&keywords=networking+for+dummies

 

[Pandasaurus]

Thanks a lot for the explanation guys, I think first of all I am having trouble understanding why a router's IP address change will prevent a pc from accessing the net since whenever my network goes down, I recycle the modem and router and all is fine again, I have never had any other problems with this in the many years I have had internet service and I have never had to do any configuration to the network. I think I will need to purchase the "Networking for dummies" handbook:

http://www.amazon.com/Networking-Dum...ng+for+dummies

Typically, it won't. The problem is accessing the router from the internet.

Another way of explaining it...

Your house has an address (well, we can assume it does). You know your address, but you also know how to physically find your house. You invite someone over who has never been to your house before. You give them your address. Now they look up directions to get to your house. But, what would happen if you give them your address, and they never look at the directions, and then your address changes? Now, they have the address you gave them, but that is no longer your address. They can look up directions to that address, but they'll still never get there, because that's not your address anymore. You would have to give them the new address, so they can look up the correct directions.

It's the same concept with your router. From your end, you know how to get to your router, and your router knows how to get out to the internet. But if you tell somebody the address of your router is (for example) 65.65.65.65, now they know how to access your router. You reboot your router, and are assigned a new address. Now, your address is 56.56.56.56. The person you gave your address to still has the address you gave them, but that will no longer get them to your router. But, you can still get out to the internet, because your router still knows the directions.

 

[mikehende]

But if you tell somebody the address of your router is (for example) 65.65.65.65, now they know how to access your router. You reboot your router, and are assigned a new address. Now, your address is 56.56.56.56. The person you gave your address to still has the address you gave them, but that will no longer get them to your router.

Nice analogy, thanks! Ok so the Router ip has a new address when you restart, now how does the public [anyone on the net] someone get that new IP address please?

 

[Pandasaurus]

I can't easily answer that one, primarily because I can't remember the exact process, so...

Here's a Wikipedia article that may help.

http://en.wikipedia.org/wiki/Address_Resolution_Protocol


Or, someone else will come by shortly and explain it properly.

 

[Gryz]

Nice analogy, thanks! Ok so the Router ip has a new address when you restart, now how does the public [anyone on the net] someone get that new IP address please?

The idea is that people at home only do outgoing connections. And they won't get incoming connections, so nobody needs to know the ip-address of a home-connection.

Some ISPs will give you always the same IP-address. In my country all ISPs do that. Some ISPs will set up dns-names and reverse-mappings for your IP address. My ISP even lets me set a domainname for my ip-address. So I can always do an ssh from anywhere on the Internet to my home machine via "ssh gryz.myisp.nl".

ARP has nothing to do with that.

BTW, if you want to learn something about networking, buy a beginner's book. Or follow a course. Networking is a field inside computer science of it own. People have university degrees in networking, they write books, dedicate their whole carreer to networking. You don't need to do all that when starting, of course. But if you believe you can learn network "just by memorizing a few web-pages", you are severely underestimating the scope and complexity of even the basics.

 

[mikehende]

As mentioned in my earlier post I will be ordering the Networking for dummies book, meantime, I got the basic help I will be needing narrowed down, here's the scenario. I will be working on POS systems installed with XP, the POS system will have a couple of servers and a touchscreen client and I will not be responsible for a customer's internet service, I will only be responsible for the backend of the router.

So I've been told what I will be needing is to know how to check each pc on the network for issues whenever one is not communicating with the other. So let first start by asking what possible scenarios do you guys think I will be encountering please?

 

[mikehende]

To be more specific first questions after reading and trying these instructions here to see if there is a connection from my pc to my router:

http://www.dummies.com/how-to/content/how-to-ping-the-windows-network-router.html

I would like to post a screenshot of the ipconfig screen but due to security reasons I am guessing I should not post here for the public? If so, please tell me, I had thought the Default Gateway is the Modem's address but now I am thinking the gateway address is the router's ip address? If this is correct then does this mean the modem will have an ip address of it's own? if yes, how do I ping the modem to find it's ip address?

 

[mikehende]

Oh, to clarify guys, I have verizon FIOS, there a is huge box on the wall [I am guessing that is my "modem"?] and a router is connected to that big box which is why I am asking if that bix box is a "modem" then does it have it's own ip address and if yes, can I ping it?