Virgin router brings down ethernet

[akis_t]

Hello

I have a simple wired network at home with a central 8 port 1Gb switch/hub Netgear.

Everything can see and ping (almost) everything else on the network.

However very occasionally the ethernet goes down. This is a very weird issue, as all devices are powered on, and how is it possible I cannot ping my printers, or other devices since they are all wired?

After months of tracing the issue, today I have discovered that simply switching the Virgin Broadband router on, or simply plugging it in to the switch, brings the ethernet down. As soon as I unplug it or switch it off, the ethernet comes back to life. I have tested two ethernet leads between the Virgin router and the switch and it is not a dodgy cable.

Therefore the Virgin router does something to "block" the central switch. But only very occasionally. For example this morning the issue started when I switched everything off, and then back on again. I traced the issue, satisfied myself that it is the Virgin router that causes it, and then after 3-4 tries of switching the Viorgin router on and off, it now works OK again. It may stay like this for weeks, months or it may cause "spikes", who knows.

I am not sure how the (Netgear) switch operates, but if, say, port 1 wants to talk to port 2, how would port 8 (the virgin router) prevent it? The lights on the ethernet sockets are on, there is no indication that plugging in the virgin router or switching it off/on somehow "fries" the switch.

Of course in the beginning I suspected the switch, so I switched it off and on to no avail. But I remember that in the past I was using other brands, an Edimax and another, and even then I was getting similar issues.

Any ideas?

 

[sdifox]

Err you sure the virgin box is a router?

 

[akis_t]

The Virgin router is a wireless access point, router and modem in one box just like the Talkttalk, BT and other similar routers. I do not use it as an access point or as a router but only as a modem. It connects to the rest of the home network with one ethernet cable only on a central switch. The problem is that very occasionally, somehow, it "freezes" the switch that it is connected to. Unplug the cable from the switch and the netowrk works again.

 

[sdifox]

The Virgin router is a wireless access point, router and modem in one box just like the Talkttalk, BT and other similar routers. I do not use it as an access point or as a router but only as a modem. It connects to the rest of the home network with one ethernet cable only on a central switch. The problem is that very occasionally, somehow, it "freezes" the switch that it is connected to. Unplug the cable from the switch and the netowrk works again.

if you disabled the router component then that is the problem. you need a router between your network and the modem. it provides firewall, nat and dhcp functionality that a switch does not.

 

[matricks]

if you disabled the router component then that is the problem. you need a router between your network and the modem. it provides firewall, nat and dhcp functionality that a switch does not.

If the problem disappears when he unplugs the modem, then surely this isn't the problem.

I understand OP as so: the modem will cause the switch to freeze, meaning no device connected to the switch can reach any other device connected to the switch. The switch cuts all communications.

Engergy-Efficient Ethernet (802.3az) is known to cause problems like this if one or both devices have implementation bugs, or other incompatibilities. Problems can also arise if one device supports EEE and one doesn't (again, bugs). EEE is supposed to put Ethernet links in sleep mode when they are not needed, to save power. One device going to sleep, and the other being unable to wake it up again would lead to something like OPs scenario.

If you can find specifications on your networking gear, see if they implement it. Then, see if you can turn it off.

 

[akis_t]

matricks thanks. It seems you understand the problem correctly. I will look into the problems you have mentioned.

The switch however should not completely freeze all other ports just because one of the ports is misbehaving/sleep/whatever? It is a netgear FFS.

But I have an idea. What if the Virgin router somehow has got into a strop and is flooding the port? Maybe that is preventing the switch from servicing the other ports? That would explain how unplugging it instantly fixes the problem, then switching the switch off and on does not fix the problem, and rebooting the router did not fix the problem the first time, but on the second.

 

[Mushkins]

But I have an idea. What if the Virgin router somehow has got into a strop and is flooding the port? Maybe that is preventing the switch from servicing the other ports? That would explain how unplugging it instantly fixes the problem, then switching the switch off and on does not fix the problem, and rebooting the router did not fix the problem the first time, but on the second.

So if I'm reading your description right, when the router misbehaves then not only internet service is cut off, but none of your devices connected to the switch can even talk to each other, correct? It definitely sounds like the router is occasionally generating some sort of broadcast-storm type traffic thats overloading the switch and creating a denial of service situation where the switch simply cannot pass traffic between devices on the network.

Could be a faulty router or a misconfigured protocol, from my experience configuring residential-grade modem/router combos provisioned from an ISP is usually a recipe for a sad network. They cut so many corners on those combo devices it's not even funny, they're universally junk.

What kind of internet connection is this? Cable? DSL? Fiber? If it's fiber I would get the ISP to switch you to an ethernet-based connection so you don't even need a modem, and replace the combo device with a decent dedicated router. If you can't do that, then ask the ISP for a device that is strictly a modem and again, use your own router.

You could also try updating the firmware on the router/modem combo. Could be a known issue that has long since been addressed.

 

[VirtualLarry]

Could this be a case of the router supporting spanning tree, seeing a loop on the switch, and cutting the switch competely off from the router?

 

[JeffMD]

If the virgin mobile device is supplying you internet, then it MUST act as a router ( doubt it will play bridge). If the device is not plugged into an uplink then there may be conflicting dhcp settings going around as both the switch and the router are supplying different settings.

 

[VirtualLarry]

If the virgin mobile device is supplying you internet, then it MUST act as a router ( doubt it will play bridge). If the device is not plugged into an uplink then there may be conflicting dhcp settings going around as both the switch and the router are supplying different settings.

Eh? Switch shouldn't be supplying any settings. Switches don't DHCP. (Consumer switches, at least.)

 

[Puffnstuff]

Is dchp enabled on your modem?

 

[XavierMace]

OP: You've neglected to mention the second router/modem you mention in your other thread.

 

[akis_t]

It is a star configuration (almost). The centre is the 8 port switch. Around this switch I have connected two printers, one homeplug device, another switch which serves another part of the house and finally the two ISP router/modems. The remote switch is also a star (switches are stars in general) and supports a WAP as well as three rooms in the house.

The DHCP server runs on one of the two ISP modems depending which ISP I prefer using. If you run both the DHCPs together then it is random when devices connect who is going to get what IP address and gateway.

Example of mobile phone connecting to the network: 1) wifi connection to the WAP 2) receives IP address from one of the two ISPs . From ISP modem/router to switch, then to remote switch, and finally to WAP and to mobile phone. Sending a packet to the WAN would be the opposite. From mobile phone to WAP, then to the LAN, then to the remote switch, then to the central switch, then to one of the two ISP modem/routers, then to the WAN.

If we remove the two ISP modems/routers from the central switch nothing will happen except we will not have DHCP anymore and no internet. But we can still send stuff to the printers and we can still communicate between devices. Various laptops and PCs have static IP addresses and those can always see the LAN even if the modems/routers are down.

 

[sdifox]

Does the network go down only when both WAN are connected or independent of that?