questions about LAN (Local Area Network)

[jimdagys]

I am on a LAN and one day I couldn't get to the internet. The connection icon on the taskbar said I was connected (see first screenshot) , but I couldn't access any websites. I went to "My Network Places" (see second screenshot) and saw something I had never seen before. I had never seen the TP-Link router icon before and I knew that had something to do with my not being able to access any web site. I had the tech people come over and they said anybody could put a router on the network (they couldn't stop anybody from doing that) and that when there was a router on the network, I wouldn't be able to access websites unless the tech people typed in some special numbers (see third screenshot). The third screenshot shows the normal configuration (obtain IP address automatically). They typed in some special numbers in "Use the following IP address" and "DNS server". My question is, why did a router make it so I couldn't access web sites using "obtain IP address automatically"? Is it true that anybody can put a router on the network? What do you think was the purpose of putting a router on the network? Shortly after I complained about this, the router icon disappeared and I was again able to connect to the internet using "obtain IP address automatically. Also where did the tech people get those IP address numbers? Is there only one set of IP numbers that will work, or are there multiple numbers that will work? In general, is it better to connect to the internet by "Obtain IP address automatically" or is better to connect using specific IP address numbers?
A lot of questions, I know but I have always been confused about this topic.

[guns1inger]

Those are not IP addresses, they are shares on other machines. I don't know who controls your network, but on the networks I run, nobody puts connects network equipment without permission. As to why it screws your access up - it depends where the router was placed and how it was configured. It could easily be set up to block your access to the gateway or proxy server that you need to access to get out to the internet. This could be intentional, or it could just be poorly setup. Given it seems to have just been put onto the network arbitrarily, I would guess the latter.

[jimdagys]

Well, this is all very confusing. One other thing I noticed (see screenshot) is that when the router icon was displayed, also in the "Network Connections" folder I could see (circled) "Internet Gateway/Internet Connection"icon. Under normal conditions I don't see that Internet Gateway/Internet Connection icon.

[Nelson37]

Some idiot screwed up.

This is one reason I hate DHCP, this is a router, or server, handing out these addresses for you to obtain automatically. Every network has an addressing scheme, typically 192.168.1.xxx, where the xxx is unique to each piece of hardware, the gateway points to the box connected to the Internet. You can have segmented networks with different schemes, but typically everyone is on the same scheme, or neighborhood. That's the first three octets, or 3-digit numbers, before the xxx. Every XXX must be different on the same network segment, other than that it does not matter what number is used. It is possible for the router to allow a certain range, Sprint DSL modem/routers typically are 192.168.0.1, and only allow 192.168.0.2 to connect. So you put a router at 192.168.0.2, and create a different net segment to the router on 192.168.1.xxx, which the DSL modem does not know or care about.

Routers will often fail to perform DHCP while otherwise working fine. If you have both a switch (hub) and a router, DHCP failure kills both Internet and internal network. Static IP addressing will keep the internal network up even if the router is completely removed.

There's a whole bunch of math involved as to how many numbers are available, 1-255 is the max range. For small nets, I often use something like 10.10.0.xxx, minor security measure.

DNS is like the internet phonebook, these are servers out in the internet somewhere. When you type a www.google.com, a request goes to your listed DNS to get the IP address for the site. Doesn't typically matter which ones are used, just that they are valid.

When the addresses are specified, there is just one less thing to go wrong. If this had been done before, you would not have had a problem, unless the idiot pulled the cable for the Internet from the working router and put it on the new one. Moron.

Yes, anybody who can open a cardboard box and plug in a power cord can do it. You can no more prevent this than you can keep someone from plugging in a lamp. Company policy should be that anyone who does this is out on their ass the same day.

[Krispy Kritter]

Your first image showing your "Local Area Connection" connected at 100Mbps is only showing your connectivity to the switch. A Simple network would have your pc connected to a switch, the switch connected to a router, and the router is connected to the internet. So your connection to the local switch was still active. You would then still be able to see other users/hardware that are connected to the switch. However, the switch may or may not still have a connection to the router. The only way for you to know/troubleshoot beyond your pc, would be to know the IP addresses of the switch, router, and other equipment beyond the router. Then whenever you have issues, you can try to ping each device and see which ones are reachable. Of course most of this is beyond you, and as you have "tech people" that handle this, there likely isn't any reason for you to troubleshoot on your own. Even if you do learn how to trouble network issues and can tell the tech exactly what's wrong, any good tech/network person won't take your word for it and will perform their own troubleshooting anyway.

[gadgetguy]

@Nelson37 I can't believe I'm going to disagree with you, but...
I agree some idiot screwed up, but that's not the fault of DHCP which is a valuable tool in a network arsenal. I have never seen DHCP fail on a properly configured network. Static IP addressing is simply a nightmare on any network with more than 10 devices. As an example, one of my customers decided to change ISPs and as a result, the DNS servers of the old ISP were no longer accesible. None of the computers could access the internet until they reset their connection so DHCP could update to the new DNS server addresses. Without DHCP, I would have had to go to each computer and key those all in by hand. While I wouldn't mind charging for all that extra time, my customers are informed enough to know that it's not necessary and would question my competence.

The rest of your commentary, while not completely accurate, is OK for a basic explanation of IP numbering. and I wholeheartedly agree that anyone who plugs in any equipment without an OK from IS should be out on their ear.

[Nelson37]

First, switches do NOT have IP addresses. They are transparent.

G-guy, there's a first time for everything.

Have seen many, many DHCP failures. Specifically as outlined, you lose the router's DHCP, you lose the entire internal net. Just not needed. Usually temporary, but I have seen routers which are otherwise functional but no longer able to perform DHCP. Have also had addressing conflicts where DHCP gives same address to two different PC. Static the addresses, problem solved.

Somewhere around 30 or so, yeah, manual IP starts to become a pain. Most of my nets are below that threshold, so no problem. Even for the large ones, I still static critical personell, and the boss. Boss's PC rarely critical, but he or she better be able to surf when they want to, or it hits the fan. I just keep 1 to 10 for them and block those out on the router, then DHCP the rest. But I really, really don't like to.

DNS servers are independent of ISP. The only reason they would not work is if the new ISP is blocking them, which they should not do. I been using the same memorized ones for over 5 years, only one or two issues, and then with ISP's with questionable policies. Original ISP no longer in business in my area.

If you have a third-party router, you would have to input the new DNS there, anyway, or point it to the modem and hope it updates the new change. To many critical info's in ROM chips. A major factor for me is the lightning issue here, frequently this blanks out ROM settings. If the network is dependent on DHCP, - boom - no network at all. This is much worse than having network, but no internet. I can't be that many places at once during rainy season.

[Nelson37]

Oh yeah, and what else is "not completely accurate, but OK"?

Just so you know, there are not too many people I would even bother to ask.

[ozymango]

A major factor for me is the lightning issue here, frequently this blanks out ROM settings. If the network is dependent on DHCP, - boom - no network at all. This is much worse than having network, but no internet. I can't be that many places at once during rainy season.

Where do you live that lightning is causing your DHCP server to fail on a regular basis?

[ozymango]

Static IP addressing is simply a nightmare on any network with more than 10 devices.

I could not agree more, especially with laptops, especially with wireless laptops. Sure, if you've got a dozen or so devices, maybe I could see using static IPS, but even then it means I've gotta sit down and enter the IP address, subnet mask, and gateway in each computer ... and why? Because my DHCP server might fail?

Yeah, okay, sure, maybe if there's some weird magnetic pulse blanking your ROM chips (?) so that the DHCP part of the router fails. But does the rest of the router keep working? Related: You use static IPs on your PCs, you've gotta configure your router for your IP range and just one more thing I, personally, don't wanna keep track of.

Plus let's say your DHCP server part of your router does fail, while your network is up -- you don't lose your network address until the computer reboots, and, frankly, I'd rather know when my DHCP server is not broadcasting because it means I darn well better fix it before I got 500 irate phone calls!

[gadgetguy]

Oh yeah, and what else is "not completely accurate, but OK"?

Just so you know, there are not too many people I would even bother to ask.

That's the first three octets, or 3-digit numbers, before the xxx. Every XXX must be different on the same network segment, other than that it does not matter what number is used.

That statement completely ignores the role of the subnet mask and as such, in not completely accurate. It is possible to set the subnet mask so the gateway is inaccessible, even if the gateway and computer have adjacent numbers in the "4th octet".

There's a whole bunch of math involved as to how many numbers are available, 1-255 is the max range.

It's not really a question of math as much as an understanding of the hexadecimal and binary numbering systems.

[gadgetguy]

Have seen many, many DHCP failures. Specifically as outlined, you lose the router's DHCP, you lose the entire internal net. Just not needed. Usually temporary, but I have seen routers which are otherwise functional but no longer able to perform DHCP. Have also had addressing conflicts where DHCP gives same address to two different PC. Static the addresses, problem solved.

I haven't experienced the problems you've described and as such, I consider DHCP to be as reliable as any other facet of networked computers.

Somewhere around 30 or so, yeah, manual IP starts to become a pain. Most of my nets are below that threshold, so no problem. Even for the large ones, I still static critical personell, and the boss. Boss's PC rarely critical, but he or she better be able to surf when they want to, or it hits the fan. I just keep 1 to 10 for them and block those out on the router, then DHCP the rest. But I really, really don't like to.

Clearly we have different pain thresholds. I do set static addresses for servers, but the boss gets an etch-a-sketch.

DNS servers are independent of ISP. The only reason they would not work is if the new ISP is blocking them, which they should not do. I been using the same memorized ones for over 5 years, only one or two issues, and then with ISP's with questionable policies. Original ISP no longer in business in my area.

Not all DNS servers are independent of ISP. Both of the ISPs involved in this instance hosted their own DNS servers and blocked the other ISPs. Both of them have since been bought up and ultimately were absorbed into the Comcast conglomerate.

If you have a third-party router, you would have to input the new DNS there, anyway, or point it to the modem and hope it updates the new change. To many critical info's in ROM chips. A major factor for me is the lightning issue here, frequently this blanks out ROM settings. If the network is dependent on DHCP, - boom - no network at all. This is much worse than having network, but no internet. I can't be that many places at once during rainy season.

It sounds like poor grounding systems in your area. I only had one customer that had problems with every thunderstorm that came through and it was because they built on a clean sand base with a poor ground system. After putting in a series of ground rings the problems decreased significantly.

[Nelson37]

I live in Southwest Florida, the lightning strike capital of the world. I have seen lightning bolts spiderweb across the entire visible sky, strikes literally out of a clear blue sky. We also have a LOT of new construction sometimes not to the highest quality standards, and a high water table, with sand as opposed to dirt. Grounding issues out the ying-yang. Ground flat as a pancake, no high ground. 20 feet is a big hill.

There are photographers who have moved to this area to make a living taking pictures of lightning. Our seasons are tourist season and rainy season.

OK, subnet masks are beyond the scope of what most people are familiar with, I only have two such segmented networks. I consider Hexadecimal and binary operations as math. I am in agreement with your statement, it just doesn't affect too many people. Those that it does, usually have a dedicated IT guy.

You may have heard (seen?) me discuss APC battery back-up units. They are absolutely mandatory here, I can tell new transplants because they don't have one.

DHCP failures are quite common, most of my customers are in the 5 to 15 unit range. My largest regular with 50 or so is way out in the boonies, in two metal buildings. He gets hit directly or nearby two to three times a year, power outages and brownouts are also common. Over half the PC's are intermittent usage as field personnel come in and boot up, no DHCP, no net.

Government buildings are about the only over-1000 unit nets here, very few others even approach 100. No heavy industry, mostly service-related small to medium-fry.

No need to set the range in the router, we keep a list and I have a system. Printers over 200, building A is odd, building B is even. Router is one and server is two.

My visitation is opposite what you guys are describing, with DHCP I had to repair this 2-3 times a year, with everyone recently booted having no net at all. Static IP, all that went bye-bye. Office manager has been trained to install the addresses, takes seconds and only needed on a new PC. Wireless units I just screen off the top 20 or so in the router for these.

I've seen 8 to 10 NIC pop at the same time, 2 or 3 PC's actually catch on fire, modems and power supplies fried and melted, Switches and routers blown, exploded chips, etc. The electric co has surge protection but no parts replacement. APC has a distribution warehouse here.

[ozymango]

There are photographers who have moved to this area to make a living taking pictures of lightning. Our seasons are tourist season and rainy season.

My wife's from Florida (Daytona Beach) and the one thing she really misses is lightning and thunderstorms, go figure. Me, I don't mind rain at all but I really, really dislike thunder, I'm like a dog on the fourth of July when those things go boom in the sky.

[gadgetguy]

Given the differences in work environments and experiences, it's easy to understand our difference in opinions regarding DHCP.

I just hope we haven't confused the OP too much.