Sporadically Lose Connection on 3 Switches

[Craigy R1]

A friend told me to come here with my problem, hope somebody can advise.

I have a tplink router and 3 tplink 8 port unmanaged switches

The router is wired to Switch 1 which is then wired to Switch 2 then from Switch 2 to Switch 3 (I have different devices plugged into the switches but maybe 2 or 3 devices are on at the same time.

Everything seems to work but sporadically I lose connection from Switch 1 to Switch 3 (devices plugged directly into the router still work and wireless still works but everything in the switches lose connection)

The weird thing is, if I unplug the cat cable from the back of Switch 3 (which goes to Switch 2) then plug it back in I get connection back on all devices in the Switches yet instead of doing that, if I unplugged Switch 1 from the router and plugged it back in I still have no connection.


Can anybody advise why it may be dropping connection?

[icecream-guy]

if they were hubs, I'd think broadcast storm.  otherwise, have you tried a different port or cable?

[Dieselboy]

What's this cable in the back of the switch? Is it a special uplink port or something? What if you use a normal front facing port for connecting the switches? To test if it's an issue with the port.

Does the problem go away if you reboot the switches? I mean for any period of time after the reboot.

[Otanx]

How often does this outage happen? Once a day? Once a week? Also if you don't do anything does it recover on its own, or does it stay broke till you do something?

-Otanx

[Craigy R1]

if they were hubs, I'd think broadcast storm.  otherwise, have you tried a different port or cable?

The 3 switches are TP-Link TL-SG108 8-Port Gigabit, I have tried plugging into different ports on the switches. I have not tried different cable, the existing cables go from downstairs to upstairs, around corners, under carpets. I could buy some new cable and run it around the house in the open and test for a week or so but the other half won't want to be tripping over it during Christmas.

[Craigy R1]

What's this cable in the back of the switch? Is it a special uplink port or something? What if you use a normal front facing port for connecting the switches? To test if it's an issue with the port.

Does the problem go away if you reboot the switches? I mean for any period of time after the reboot.

I'm a layman at networking so not totally sure what you mean. The TP-Link TL-SG108 8-Port Gigabit switches have just 8 ports on the front, the cable used is 1x30m and 2x 15m of this amazon.co.uk/gp/product/B00WD017GQ/

When I lose connection it is everything in switch 1, 2 and 3. Sometimes I can unplug switch 3 and plug it back in (either the power or the cat cable from switch 2) and all connection comes back but sometimes that doesn't work and I have to unplug Switch 2 or 1.

[Craigy R1]

How often does this outage happen? Once a day? Once a week? Also if you don't do anything does it recover on its own, or does it stay broke till you do something?

-Otanx

I started to write it down every time I had to unplug/replug, I don't know the exact times as I can wake up in the morning and find a device no longer connected like the xbox (where it is moaning it hasn't got DHCP then I look at all the other devices in the 3 switches and they are not connected either). So the last two times have been approximately 4 days between them going down. So went approx 4 days connection is great, lost connection unplugged / replugged, connection great for approx 4 days then no connection.

I have in the past left it and gone out the house for a few hours (without unplugging the cat or power cables in the switches) when the connection went down, when I came back home they were connected again without me doing anything.

I have tried different switches (before I had 3x even cheaper 5 port TP Link switches).

[icecream-guy]

I wonder if the issue is this green "feature" of the TL-SG108

Power down Idle Ports
When a computer or network equipment is off, the corresponding port of a traditional switch will continue to consume considerable amounts of power. The TL-SG108 can automatically detect the link status of each port and reduce the power consumption of ports that are idle, resulting in up to an 82% reduction in power use.

[deanwebb]

^ I'm with the idle ports explanation. Also, connecting switches like that is not a good thing. I've seen it lead to other problems, so it's better to get longer cables and connect them all to the router or directly to switch 1.

[Craigy R1]

I wonder if the issue is this green "feature" of the TL-SG108

Power down Idle Ports
When a computer or network equipment is off, the corresponding port of a traditional switch will continue to consume considerable amounts of power. The TL-SG108 can automatically detect the link status of each port and reduce the power consumption of ports that are idle, resulting in up to an 82% reduction in power use.

Every switch I look at from different makers seems to have green tech ports.

[Craigy R1]

^ I'm with the idle ports explanation. Also, connecting switches like that is not a good thing. I've seen it lead to other problems, so it's better to get longer cables and connect them all to the router or directly to switch 1.

I looked it up before doing it and it said linking 3 switch boxes max would be ok, no more than that. Maybe that is the problem though. I might take switch 3 out of the equation for a week and test to see if I still have dropped connections.

[deanwebb]

^ I'm with the idle ports explanation. Also, connecting switches like that is not a good thing. I've seen it lead to other problems, so it's better to get longer cables and connect them all to the router or directly to switch 1.

I looked it up before doing it and it said linking 3 switch boxes max would be ok, no more than that. Maybe that is the problem though. I might take switch 3 out of the equation for a week and test to see if I still have dropped connections.

3 is the practical max, but you still encounter performance issues from cascading switches like that. With gear like this, the flatter the structure, the better. In big businesses, they'll have a core switch, distribution switches, and then access switches where the endpoints all plug into and then zero cascading of access switches... if they're doing it right.

[Dieselboy]

The router might be classed as a switch here, because it may have a switch for the LAN ports. Is it possible to go: router -> switch 1/2/3 ? ie the switches all connected to the router like Dean suggested?

When the devices are off the network whats the status of the switch LEDs including the port LEDs ?

Whats the model of router that you have? When the devices have lost connection, are you able to log in to the router and check the port that connects to switch 1? I am thinking it could be an issue between the router and first switch. I am thinking something like spanning tree (or that power saving feature) blocking the link between switch 1 and the router, and then eventually losing dhcp from the router.

[Craigy R1]

The router might be classed as a switch here

Just a shortish update. I decided to buy a different router (draytek) as the previous router (TPLink vr2600) had not been updated by TPLink for years and also it never got IPV6 properly, TPLink promised multiple times by email they were working on firmware to fix it but it never came. Which is why I won't be buying another TPLink router again.

Anyway I put the Draytek in and tested and after a few days it dropped the connection again like before. So not a specific router problem.

I ended up putting the switch 3 directly into the back of the router and left switch 1 and 2 linked how it was before and tested and the connection has been perfect (When I read up on switches and saw you could daisychain 3 I didn't understand that the router was maybe classed as a switch)


So switch 1 and 3 are directly in the back of the router and I've decided to pull up the carpets and run switch 2 directly into the router that way everything is done then even though it is a bit more work. Also I obviously needed longer cables so got some cat 7 instead though I won't be taking full advantage of it right now.

In closing everything is working, I now get ipv6 and Draytek seem to support their products for longer and push out updates.

Thanks for the pointers guys.

[Dieselboy]

Good to hear you have it sorted Draytek are usually decent routers in my experience.