Why does the router go crazy with broadcasts?

Question

network hardware

Hello, there was not a big incident some time ago ... now it has long been eliminated by switching to its own channel from the provider.
So some time ago, there was an organization, let's call it Alpha, which has about n workstations in its environment, + network org equipment.
A new institution, let's call it Omega, needed the Internet when it opened, and until the moment when it concludes an agreement with a provider for a dedicated channel for itself, it took a lot of time, you know, money problems ...
Knowing that there are a couple of Alpha offices near the Omega offices, I thought , and why not use Alpha’s channels for the time being, this should not be a problem for them, Alpha was almost not opposed ...
And so I stretched a cable from one of the Alpha offices to the Omega office, installed a switch, and put it in places for users. Everyone rejoiced and idolized me. Joke.
But a few days later, my friends from Alpha called me and said that they did not have enough ip addresses on the dhcp server. My users took over the address and as a result, some Alpha users were left without access to LAN and WAN. For example, the chief accountant ...
I was thinking, why don't the guys just allocate one more network for us, they had a "typical network", 192.168.1.0/24, as far as I know they did not use VLANs , and ms server 2008 (most likely) acted as DHCP and DNS servers.
They didn’t want to muddy the waters, or they didn’t know how (is this possible?), But they refused to allocate for the network for us.
It was decided to take 1 address from their LAN and NAT it.
I had 2 office wifi routers at hand, Asus RT N16 and TP-LINK WR941N.
When using any of them, after a while the Internet regularly disappeared from users, and the router itself went crazy with broadcasts, its lights on the ports were constantly blinking at high speed.
Now the problem has already been solved, everything is in order, we have our own Internet channel, and everyone idolizes me. Again a joke.
The essence of the question: why did the router go crazy? after all, he NATed only about 20 machines ....
That is, Alpha's LAN from about 200 machines and org equipment, 1 cable went to my router, which NATed another 20 users.
I understand if it NAT'd 200 machines, but it's not designed for such a load...
PS If I wrote any stupidity that causes bathhurt in you, please forgive me because I am a student, relatively stupid, but adoring linux and crutches, and having a hatred of microsoft. Just correct me, or stick to the right link.

Answer 1

When using any of them, after a while the Internet regularly disappeared from users, and the router itself went crazy with broadcasts, its lights on the ports were constantly blinking at high speed.

I don't understand what broadcasts have to do with it. It is logical to talk about the nature of traffic, having dumps of this traffic or indirect data (broadcast packet counters on interfaces). Not sure about flashing lights.

The essence of the question: why did the router go crazy?

Assuming that it's all about broadcast traffic, it's most logical to look for its source in your local network. If you have configured routing between the WAN and LAN ports of the device, then the broadcast packet from the WAN port should not be redirected to the LAN ports. One of the options, you had an L2 loop in your local network. Possibilities for a loop to occur: bridging on the server, bridging on the IP phone, bridging between LAN and WLAN on the client device if the WiFi access point is also configured in bridging mode.
Another option is that traffic from the Alpha organization (including multicast / broadcast) loaded your router's processor, and it could no longer cope with the workload.
It is difficult to assert the correctness of any one hypothesis without actual data.

Answer 2

all these routers are Asus RT N16 and TP-LINK WR941N. homemade and serving 20 clients is a lot for them, buy soho equipment