internet stop work when someone specific connect

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zivkovic.pp

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Aug 17, 2017
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10,510
In the firm we have 1 modem and maybe 10+ routers connected to modem. Yesterday internet stop work, we have signal but no access to the internet. I find out that when I disconnect one specific router, internet immediately work. So i tried to restart that router and connect him again. Internet was workin around 20min. In that time 15 user are connected to that router and internet stop work again. Now i changed wifi password and internet still working, no one knows password now. What can cause the problem, can I find out which user make problem? Can router make problem? Do someone want hack us? We don't have any business on internet so is uselles to have our network. I think problem is in some device, i tried to eliminate some user but i failed. How can i test network and user to find which one make problem if problem comes back.

sry bad english..
 
Solution
Ralston18
Only the main router should be issuing DHCP IP addresses.

All other routers should be assigned a Static IP address outside of the main router's allotted DHCP IP address range. Each router's assigned static IP should be reserved on the main router via the static router's MAC.

There are a variety of apps that you can used to scan your network for IP addresses.

For example: Nmap-Zenmap GUI, Spiceworks, Wireshark, Wife-Network Monitor.

May or may not be entirely suitable for a large network such as yours. However, you should be able to gather enough information to get a sense of what is happening.

Look for duplicate IP addresses or some misconfiguration. Start with the problem router.
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Ralston18

Ralston18

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Oct 11, 2014
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10 routers on one modem?

How many users if everyone is online?

You originally narrowed it down to one router.

Get back to that router and start adding the user's back one by one. Hopefully all will work until the "someone specific" connects.

My thought is that there is an IP address conflict: two computers/routers whatever having the same IP address.

Draw a picture of your network. Show the modem, the routers, and all the end user connections. Write down each device's IP address. Every device (modem, router, printer, NAS, computer, etc.) should have a different IP address and the same subnet mask.

Be sure that only one router ("Main router") is issuing IP addresses via DHCP. Someone may have reset one of the other routers (probably the one "specific" router that you found) and now two routers are providing IP addresses.

The goal is to look for IP address conflicts within your network.






 
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Z

zivkovic.pp

Honorable
Aug 17, 2017
12
0
10,510
Hey,

I can show network map from modem, there is actually 7 routers connected to modem. This is the link of network map " http://prntscr.com/g9ziiv " last unknown router is router who have problems. How can I see all user on network? We have around 200 people in building who work here and they probably all use internet.

Before three days I change wifi password of that specific router, and internet still working there is no user now connected on that router.
 
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Ralston18

Ralston18

Titan
Moderator
Oct 11, 2014
35,033
3,356
146,290
Only the main router should be issuing DHCP IP addresses.

All other routers should be assigned a Static IP address outside of the main router's allotted DHCP IP address range. Each router's assigned static IP should be reserved on the main router via the static router's MAC.

There are a variety of apps that you can used to scan your network for IP addresses.

For example: Nmap-Zenmap GUI, Spiceworks, Wireshark, Wife-Network Monitor.

May or may not be entirely suitable for a large network such as yours. However, you should be able to gather enough information to get a sense of what is happening.

Look for duplicate IP addresses or some misconfiguration. Start with the problem router.
 
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