Wired network troubleshooting

[redzoneos]

Hello all! I'm looking for advice on most cost effective way to troubleshoot a wired network failure (internet via WiFi works fine). I don't want to start just buying/replacing parts if there is a way to solve the problem without.

Anyway -

Motorola modem sbg-6580. WiFi is disabled.

Netgear nighthawk r7000 router.

I have a zyxel 16 port switch that connects cat6 throughout my house.

I have a netgear 4 port switch in the family room and another dlink 4 port switch in my bedroom.

Problem:. Random network failure. I lose connection, it comes back, goes, etc. Rebooting ANY portion of the network seems to bring it back for a while until it fails again (sometimes minutes, sometimes days!)

Mostly I observe this in the bedroom since probably 90% of my wired usage is there (PS4, PC, etc).

I've tried swapping the 4 port switch locations, changing up the wires, updating firmware for the modem and router etc.

My thought at this point is:. Either a bad network cable going into my bedroom (haven't been able to consistently test the family room unfortunately). Or bad modem/router/16 port switch.

I don't have spare equipment so how do I test the hardware for possible failures? Especially since it's intermittent, I am not sure.

Any suggestions/tips are welcome!!

 

[Solandri]

Motorola modem sbg-6580. WiFi is disabled.

Netgear nighthawk r7000 router.

How are these two connected? Since the Motorola is a combination modem/router, it is providing a DHCP server. If you plug it and the Netgear router together on the same LAN, you will have two DHCP servers, which can cause the problems you're describing (random network failures which can sometimes be temporarily resolved by rebooting the device). WiFi wouldn't be affected because only the Netgear is providing WiFi, so it intercepts WiFi DHCP requests before they can be relayed to the Motorola. DHCP requests over Ethernet however get fulfilled by whichever router responds first.

The correct way to configure two routers is to either:

• 
  ■Disable the DHCP server on your Netgear router. Basically turn your Netgear router into a switch/wireless access point. Do not use the WAN port on the Netgear (put a piece of tape over it). Only use the LAN ports. Internet management (e.g. port forwarding) will be handled by the Motorola modem/router.
  ■Or plug the Netgear router's WAN port into one of the Motorola's LAN ports. Assign the Netgear router's WAN port a static IP address on the Motorola's LAN. Configure the Motorola so that the Netgear's IP is DMZ (this will forward all ports to the Netgear, making the Motorola invisible for port forwarding purposes). Your Netgear router will then control your LAN, WiFi, and Internet. It merely passes Internet traffic through the Motorola.

 

[redzoneos]

Thanks solandri. I'm away right now so Ill need to confirm tomorrow but I'm fairly confident I have it set up in the opposite direction of your suggestion.

Would that matter?

99% sure I have wifi/DHCP/etc all disabled on the Motorola combo... It functions only as a standalone modem.

The r7000 supplies DHCP, up addresses, and all normal "router" functions.

I'll post back tomorrow after confirming. If both units are acting as router though, would I not also have different or overlapping networks to connect to? E.g. "home1" and "Home2"??

 

[failboat]

Nested routers will make port forwarding difficult. It shouldn't cause any other issues as long as they are using different ip ranges.

Pass through on the modem is preferable. You can check the 2nd routers WAN ip and see if it's private (192.168.x.x) or public.

The cascaded switches are more likely to be the issue. Blasts over layer 2 can cause loopbacks. Test with none of the extra ones turned on. If one of them is really old, swapping it out for a new one will likely fix the issue.

 

[redzoneos]

I'm sorry for the delay in responding but I wanted to a bit more troubleshooting before posting back.

I did factory reset on both my modem combo, along with the router. I then followed steps to disable dhcp/wifi etc on the modem combo (basically disabled everything so it's a barebones modem only)

Then I recreated my wifi network and power cycled all of the switches, etc.

This "solved" the problem for the past four or five days, however it was not a permanent solution. I'm having problems again, same issue as before. I can reboot devices and restore service, but over time (usually a matter of minutes or hours) I lose it again.

Wifi continues to work with no issues.

Sooooooo... Can this still be a modem related issue with DHCP assignment?

I canl disconnect all switches and wire direct to router to test that way, however this will be difficult to do for longer term testing since no device is close enough for a direct link. Ideally I'd prefer to explore other troubleshooting before going this method since it would essentially disable all of my wired devices for several days.

Any other tips??

 

[failboat]

pass through would have it's own section in the modem/router. Otherwise the NAT might still be running.
To troubleshoot this make sure you can log into the 2nd one and check the ip it's getting. If it's a 192.168.x.x then the modem is still running the NAT.

I'd recommend leaving DHCP on and make sure only the WAN port of the other router is plugged in.
Turn wifi off of the modem/router.
The model I configured didn't have a one button setting to make it a modem. I had to configure the passthrough menu and I think it was in the firewall section maybe.