Lost Internet after you connect multiple PCs. Why?

Good day to all. Recently I was asked to help at a local school. The bottom line:
Internet access is just across the school, except for room # 2. After the group of computers located in office No. 2, give Internet access, it falls in the whole school, except this office.
Objective: to Establish Internet access in all rooms.
All computers are connected in a separate LAN, on the principle that the office - LAN. In the offices use the switches.
The question, I think, is clear: where do I start?
Could there be a problem in computers in office # 2? Is it possible that they block Internet access in the whole school?
June 10th 19 at 15:23
3 answers
June 10th 19 at 15:25
where do I start?
I think we should start with an invitation specialist.

Could there be a problem in computers in office # 2? Is it possible that they block Internet access in the whole school?
No.
Well, why not. It is not excluded, for example, that some of the components is a torrent client that blocks the entire channel. - Evangeline.Waters97 commented on June 10th 19 at 15:28
,
he falls in the whole school, except this office.
When the torrent puts the channel in the rest of the Internet will not disappear, just the speed drops and the ping will be high. - earl.Weissnat commented on June 10th 19 at 15:31
June 10th 19 at 15:27
As the Internet "give"?
Can the address conflicts occur?
Can you include a router that acts as DHCP and gives the left settings to the rest?
Start with the Internet gateway in the first place
I understand that the Internet is handing out the problematic group (room No. 2) through the teacher's computer. Either the teacher changes the settings of the router, which is in the next room. - Evangeline.Waters97 commented on June 10th 19 at 15:30
In any case, the dealer must be hateem(gateway). Of course, when the gateway changes, then everyone who is not reconfigured at it, no Internet.
I think you have addressed something.

p. s But if the old gateway will work, Internet will also be. - earl.Weissnat commented on June 10th 19 at 15:33
June 10th 19 at 15:29
Make sure there is no conflict of IP addresses between the computer Cabinet and the gateway.
Make sure that there is no inversion on the switches (such as one cable comes out and enters the switch)

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