Ethernet switch disconnects devices directly connected to G1100
mcar91
Newbie

Something is fishy with my network. I've recently added a 5-port unmanaged ethernet switch (TP-Link TL-SG105) to my network. When the switch is connected to my G1100 router, the ethernet devices attached directly to the G1100's ports cannot be reached.

Disconnecting the TL-SG105 from the G1100 solves the problem immediately. 

The network has worked for a few hours at a time without issue but eventually the G1100's "local" devices end up unresponsive. 

I realize this is a bit of an odd one, so I made a diagram to help: 

image

image

Some things I've already tried:

  • Different cables between the G1100 and TL-SG105 don't change the result.
  • I used a cable tester on the cable connecting the G1100 and TL-SG105 and all is good.
  • Got a replacement TL-SG105 and the behavior is the same. Makes me think it's the router.
  • None of the devices on my network are running their own DHCP server.
  • I've reached out to TP-Link's support and have not yet heard back but since it's an unmanaged switch, I think it's pretty benign. 
  • Wifi is entirely unaffected by this issue and continues to function even when the G1100's ethernet devices are not working.

My gut says it's something funny in the G1100's configuration. 

Does anyone have any thoughts? 

0 Likes
20 Replies
Edg1
Community Leader
Community Leader

There isn’t really any configuration for an un-managed switch. Can you account for all your patch cables? For example do you have one patch cable plugged from one lan port to another lan port? That is one thing that will cause the issues you posted about. 

Cang_Household
Community Leader
Community Leader

Edg1, I concur with your opinion.

Seems like the 4-port ethernet switch chip on the G1100 is having issues with the TP-Link. I believe that TP-Link is IGMP snooping-capable, are you running any Multicast traffic (FiOS TV One Mini uses IGMP too)?

I have a TL-SG108, the 8-port counterpart of your switch. I might need to experiment it myself with G1100, but I need to rip my network infrastructure apart 😓.

Edg1, does G1100 support STP? I see FiOS Network Adapter supports STP surprisingly.

Edg1
Community Leader
Community Leader

@Cang_Household wrote:

Edg1, does G1100 support STP? I see FiOS Network Adapter supports STP surprisingly.


Not 100% sure. I would have to look at the manual. 

mcar91
Newbie

I don't believe I have any multicast traffic on the network. I don't have any other Verizon products (no TV, no DVR, no phone, etc.). 

I have two of the TL-SG105s — only one is connected. I've swapped them out and both have exhibited the same behavior. 

Things seem to work fine for a couple hours at a time and then the only way to restore connectivity to the devices connected to the G1100 directly is to disconnect the switch. When I reconnect the switch, it typically doesn't work. I need to wait a few hours before reconnecting. 

The time element makes me think it's DHCP related but I'm not sure. Wireless devices included, there are only about 30 devices on the network. 

0 Likes
mcar91
Newbie
@mcar91 wrote:

What do you mean by “from one lan port to another lan port”? 

I can confirm no cables are plugged into the same device on both ends. 🙂

That means looping connection, assuming no Link Aggregation (both G1100 and TL-SG105 are not capable).


Re: network loops, I did some Googling and found this support article over at NETGEAR.

One of the devices on my network (connected via ethernet to the TLSG105) is a MacBook which is connected with both wifi and ethernet. Most of the time, I have the wifi turned off, but sometimes I forget to turn it off. 

I currently have the MacBook connected to both wifi and ethernet (via the switch) and everything is working correctly. I wonder if things will break when the DHCP lease goes to be renewed? It currently has 2 IP addresses (one per connection). I'd hate to think this would break everything. 

Last weekend, the ethernet-on-G1100 issue was happening and I don't believe the MacBook was connected to both at any point over the weekend. I could be wrong though. 

0 Likes
Cang_Household
Community Leader
Community Leader

I don't think it is DHCP or multiple NICs connect to the same device. What I have here is a Windows with two IP addresses on WiFi and two IP addresses on a RJ45-USB (not possible for IOS devices) adapters for redundancy and simultaneous access to two subnets.

Anything related to IP addresses is considered to be layer 3. Your TL-SG105 and G1100's LAN switch are both layer 2. IP addresses (including DHCP) are kind of irrelevant here. The document from NetGear only shows the scenario of a layer 2 loop. Technically you can have a layer 3 loop too, buy you don't have a layer 3 switch or static routing going on.

Can you maybe swap a brand for the switch? Let's try NetGear unmanaged for a similar price level. I have a Cisco switch that works with G1100. That is expensive and unnecessary though.

mcar91
Newbie

@Cang_Household wrote:

I don't think it is DHCP or multiple NICs connect to the same device. What I have here is a Windows with two IP addresses on WiFi and two IP addresses on a RJ45-USB (not possible for IOS devices) adapters for redundancy and simultaneous access to two subnets.

Anything related to IP addresses is considered to be layer 3. Your TL-SG105 and G1100's LAN switch are both layer 2. IP addresses (including DHCP) are kind of irrelevant here. The document from NetGear only shows the scenario of a layer 2 loop. Technically you can have a layer 3 loop too, buy you don't have a layer 3 switch or static routing going on.

Can you maybe swap a brand for the switch? Let's try NetGear unmanaged for a similar price level. I have a Cisco switch that works with G1100. That is expensive and unnecessary though.


I have a few things to report! First, the TP-Link switch worked for 4 or 5 days straight without any interruption. The issue reappeared over the weekend.

I then replaced it with a Netgear switch (GS-305) and the issue appeared after about 8 hours of the the Netgear switch running. Same exact symptoms — all ethernet devices directly connected to the G1100 went offline until the switch was disconnected. 

Any other thoughts? 

I reached out to Verizon's support and they won't do anything except send a tech out to my apartment which feels like a dead end. 

0 Likes
Cang_Household
Community Leader
Community Leader

I want the original poster to make two observations.

Are the LED lights still lit when the disconnection happens? 

Are the LED lights on both switches flashing crazily when you know there is no significant amount of traffic on the line? If they do, this is a sign of layer 2 or 3 looping. I wish you have my Cisco switch, it detects loops by itself and displays on the port. A flashing yellow calling for attention.image

Reposting image: deliberately created a loop for demonstrating FiOS Network Extenders cannot be uplinked by both MoCA and Ethernet.

Are your dual interfaced-Macbook's connections bridged? If they are, this is essentially having a layer 2 loop between the WiFi and the ethernet switch. Since you said the WiFi still works, this possibility can be ruled out.

mcar91
Newbie

After a few days of things working well, the issue cropped up again. I noticed the lights on the switch and the G1100 are flashing like crazy. On the Netgear switch, it’s the port my PC is using and the one running to the G1100. The port connected to my MacBook is not flashing (cuz it’s disconnected currently). 

any ideas on how to eliminate a loop on Windows? It’s only connected via Ethernet. WiFi on the machine is disabled. 

0 Likes
Cang_Household
Community Leader
Community Leader

@mcar91 wrote:

I noticed the lights on the switch and the G1100 are flashing like crazy. On the Netgear switch, it’s the port my PC is using and the one running to the G1100. 

any ideas on how to eliminate a loop on Windows? It’s only connected via Ethernet. WiFi on the machine is disabled. 


You definitely have a loop somewhere, otherwise the LEDs won't "flashing like crazy" when you know there isn't a significant amount of traffic.

For Windows bridging, go to Control Panel > Network and Sharing Center > Change Adapter Settings, see if there is a router icon as an adapter.

mcar91
Newbie

@Cang_Household wrote:


You definitely have a loop somewhere, otherwise the LEDs won't "flashing like crazy" when you know there isn't a significant amount of traffic.

For Windows bridging, go to Control Panel > Network and Sharing Center > Change Adapter Settings, see if there is a router icon as an adapter.


I'm brand new to Wireshark so I just fired it up with all the default settings. I ran two captures and the results are on this link.

https://we.tl/t-l6bMRZrfbF

"wireshark_switch_no_router" is the PC connected to the switch and the switch is not connected to the router. In this state, the light on on the port connecting to the PC was flashing rapidly. Seemingly to nowhere. 

"wireshark_switch_connected_to_router" is the PC connected to the switch and the switch connected to the G1100. When I captured this, the problem was happening. The G1100's ethernet devices were down and the PC's internet connectivity was also down. 

0 Likes
Cang_Household
Community Leader
Community Leader

First of all, sharing device configuration on third-party platforms is very insecure.

For WireShark, you are capturing the loopback traffic. You should select the Ethernet adapter. Or, you have selected Ethernet adapter and we are seeing bunch of loopback traffic? If the latter is the case, that is a sign of layer 3 looping.

Your Adapter property shows the device does not have an IP address. Did you release the IP address? None of your adapter is bridged, which is good.

mcar91
Newbie

Well things have gotten even stranger. Since the last time I posted, I replaced the G1100 with an Airport Extreme I had laying around. I also set the PC with a static IP address which I confirmed was working correctly. The network ran nicely for a few hours and then the same issue popped up. The lights on the switch were blinking like crazy and all the ethernet devices went down. The new behavior this time, though, is that all wifi devices ALSO went down.

So it's not the G1100's fault.

It's not the switch's fault because I've tried 2 TP-Link devices and a Netgear and they've all had the same behavior.

I feel like it MUST be the PC or the cable running between the router and the switch upstairs. The cable works... is it really possible the cable could just sometimes mess up the entire network?? 

0 Likes
Cang_Household
Community Leader
Community Leader

That's a broadcast/multicast storm. G3100/G1100's APs are smarter than Airport Extreme to block broadcast storms, probably.

Have you tried what I said in the previous post. I am not trying to be didactic here, I just want to be helpful.

mcar91
Newbie

Yes, I also ran Wireshark on the ethernet adapter. I'm really not sure what I'm supposed to do with that captured data. I also posted on reddit and someone there mentioned it just looks like the PC is unable to get an IP address. Nothing about what may be causing the storm. 

0 Likes
Cang_Household
Community Leader
Community Leader

Are you sure you selected the correct Network Interface?

mcar91
Newbie

I also ran the Windows network troubleshooter and it says the Ethernet network doesn’t have a valid IP and the default gateway is not available. 

0 Likes
gs0b
Community Leader
Community Leader

In the diagrams you posted, you show the cable between the router and the switch as "outdoor cat6."  How long is this cable?  Is it running between buildings or outside somewhere?

Can you try putting a switch right next to the router, then plug the run to the other switch into it?

mcar91
Newbie

What do you mean by “from one lan port to another lan port”? 

I can confirm no cables are plugged into the same device on both ends. 🙂

0 Likes
Cang_Household
Community Leader
Community Leader

@mcar91 wrote:

What do you mean by “from one lan port to another lan port”? 

I can confirm no cables are plugged into the same device on both ends. 🙂


That means looping connection, assuming no Link Aggregation (both G1100 and TL-SG105 are not capable).

Then, do you have Multicast traffic? Can you change a switch to see what would happen?