How to find out the reasons for the strange behavior of routing?

Question

Computer networks

Quite a tricky question covered in magic

Let's start with a description of the hardware, the operator is a megaphone, a HUAWEI E5572 modem, hilink firmware, the whole thing works on 4g band7, then the traffic goes to the Beeline Smart Box Turbo + router, it has a firmware from Rooter based on openwrt 19.07, the router distributes the network at 5GHz, in the firewall, the local network is combined with the wifi interfaces of the module, and a single dhcp server is working distributing the network 192.168.1.0/24, the modem also has dhcp installed, the router has ip 192.168.8.100, traffic from the router goes to the d-link dgs-1016d switch, and already from this switch there is a distribution of wired Internet to all devices in the local network. Also on the local network is ubiquiti nanostation loco m2, connected like all devices to the switch, it is configured as a soho router, all dhcp requests are sent to the main router, like everything, this is all hardware.

And the problem is this, the ping from devices to 192.168.8.1 disappears, that is, to the modem, and, accordingly, the Internet disappears, any ping disappears (except for ping to 192.168.1.1 (router)) on devices connected to any of the wifi points in the local networks (that is, for all devices that are connected to the nanostation, and that are connected to 5GHz that the router itself distributes, and even on devices that are connected directly to wifi by a distributed modem), and for devices that were connected to the network after the icmp ping was lost (for example, ping to the modem disappears, there is Internet on the main PC, but if we connect a new device to the network, then there will be a ping to 192.168.1.1 (router), but there will be no ping to 1.1.1.1 or 192.168. will not).
Also, the ping to the modem disappears from the PC, but it still has a ping on 1.1.1.1 and in general on the Internet. Also, the problem sometimes itself is solved for 10-15 seconds, then everything breaks down again.

And now what I did:
Reset the settings for both the modem and the router, solves the problem for 3~4 hours, then everything breaks again
Rebooted the modem, helps for 3~4 hours, then breaks again
Tested the wifi connection to the modem directly , also works for 3~4 hours, then the ping disappears altogether, but the access point remains working, the built-in dhcp does not distribute new ip.
Also, if you just wait a long time for the page to load, then it can load, but this happens extremely rarely. I
changed all sorts of configurations in the modem itself, and in the router, do not list, nothing helped
I changed the micro-usb cable that connects the modem and the router, it does not help Disconnect
and connect the modem without rebooting to the router, it helps wifi clients literally for 1-2 minutes, then the ping to the Internet

disappears ping to the modem is lost, there is no ping on any access point either to the Internet or to the modem itself There is nothing in the router logs. that is, there is absolutely nothing, and the modem does not lead anything (well, or I don’t know about it) And now what are my assumptions why this happens (yes, crazy, but there are no others =)

Since the modem is with a battery, and the modem is constantly connected to the router, respectively, the discharge charge cycle is constant, the battery is swollen and sometimes the modem connection with the battery may disappear, I already ordered a new battery before I arrived, but this assumption does not explain why the ping to the Internet PC does not disappear at all.
Another assumption is related to that the battery does not produce the calculated current, and because of this, some controller in the modem does not have enough energy, but again, this theory is destroyed by the fact that reconnecting to the router helps, even if only temporarily.

This problem appeared by itself.

I hope I explained clearly and correctly, I am ready to conduct any test that is required. Does anyone have any ideas? =)

Answer 1

The problem is not the modem, the problem is the router . Change to another model (not Beeline). Cellular operators and other providers traditionally provide customers with the cheapest router models. If you're lucky , then such routers can work fine. Not everyone is lucky. In addition, this hardware is designed for home use, when 5 devices are connected to it (via cable and via Wi-Fi), but you seem to have a larger load. The router stupidly can not withstand the load. It may overheat, but not necessarily, it can fail without overheating.