Internet randomly cutting out for 5 minutes several times throughout the day

[Davit2005]

The only 3 issues I've seen to cause these sort of issues were

1. Network connectivity issues caused by a network loop (user connected wall jack to wall jack), we had vlans setup so it only effected a small area (a benefit of using vlans) diagnosed by the port lights on the switch not looking normal and frantic

2. Network connectivity issues caused by misconfig on a core switch creating a loop bringing a section of the network down that the core switch was responsible for. Diagnosed by a matter of knowing someone made a change

3. Internet issues caused by a physical damage to the overhead telephone cable. Was a PITA as the ISP kept blaming our network and took days of isolating different parts of the network before ISP owned up.

[Sonic007]

I can thaknfully report we have not had any issues now for nearly a week. Yay!

[3s-gtech]

So it was one of those absent staff? And they've now mysteriously 'disappeared'? Any new road bridges being built near you?

[Sonic007]

Well the staff that were off sick are now back so I think that rules them out.

 

No bridges being built nearby. We do have contractors in resurfacing the flat roof but they arent anywhere near anything I.T. related.

 

I am going to file this one as unexplained mystery.

Edited November 24, 2021 by Sonic007

[3s-gtech]

Well the staff that were off sick are now back so I think that rules them out.

 

no bridges being built nearby. We do have contractors in resurfacing the flat roof but they arent anywhere near anything I.T. related.

 

I am going to file this one as unexplained mystery.

The construction project was more in mafia terms of 'disappearing' the perpetrator...

[MbroTech]

Had a similar issue with a satellite site some years back. Short outages that tended to happen at similar times of the day.

 

Turned out to be a crane on a local building project that was swinging by large loads that obscured the line-of-site microwave link we had been using.

 

We managed to upgrade to a fibre link after that.

[Jawloms]

I had an issue at a primary school many years ago where the Internet would drop out randomly for a few minutes. It was in the days of ISDN internet, and it was free between 8am and 4pm on weekdays. They used one of those programmable timers to turn it on and off. I eventually found that the timer also had a "Lamp mode" where it would randomly turn on and off on the assumption you've plugged a light in and then it makes your house look occupied! They felt very silly when I found that one.......

[Sonic007]

I had an issue at a primary school many years ago where the Internet would drop out randomly for a few minutes. It was in the days of ISDN internet, and it was free between 8am and 4pm on weekdays. They used one of those programmable timers to turn it on and off. I eventually found that the timer also had a "Lamp mode" where it would randomly turn on and off on the assumption you've plugged a light in and then it makes your house look occupied! They felt very silly when I found that one.......

 

It is indeed the little things that can often have such big consequences.

[Andrew_C]

I may have said before -

 

A friend was working in an office block on a very similar problem. At random times, the network collapsed with all sorts of weird symptoms. Of course, it wouldn't do it while they were watching.

 

Sitting on the corner of a secretaries desk, flirting, he asked what they do when it is broken - "Watch the boats in the Manc ship canal going down in the lock".

 

Which was where the earth plate for the building was. The water cleared the plate, a voltage between true earth and the signal earth of the network was established, and the equipment fell over.

[Sonic007]

And it has started again...... After a whole week without any problems....The random Internet cutting out is back again.

 

It has happened atleast 5 times today. Random times. Lasts about 3-4 minutes.

Can ping router, but nothing on the Internet. Tracert stops after router.

 

I cant work out what it could be!

Edited December 1, 2021 by Sonic007

[Oaktech]

And it has started again...... After a whole week without any problems....The random Internet cutting out is back again.

 

It has happened atleast 5 times today. Random times. Lasts about 3-4 minutes.

Can ping router, but nothing on the Internet. Tracert stops after router.

 

I cant work out what it could be!

 

I'd be throwing that back to your ISP at this stage. nothing inside your network has changed.

[Michael_Ox]

Experienced this at a previous workplace running UniFi AP's (AC-PROs). They were working on a firmware fix for wireless devices not working well with third party DHCP servers which caused the APIPA. As for wired devices, they were unaffected.

[Michael]

What are you using as an edge router?

 

Try using an unused Ethernet port, along with a device configured with a static IP ready. This is a simple enough test, which will immediately prove if it's a LAN issue or not.

[midweek]

Had a similar thing a year or two back which turned out to be a DDOS attack (DNS Flood, presumably paid for by some students) that would last for about 5-10 minutes and then everything would go back to normal.

 

Our ISP confirmed it but said our 1Gbps link was "too small" to trigger their DDOS protection.

 

We had 4 or 5 WAN IPs and switching between them immediately resolved the issue. Couldn't find any tell-tale IP Location searches on our Smoothwall so never did catch the culprit.

 

Also have Unifi kit and have just resolved a bunch of problems by removing a couple of LAGs between Netgear switches. Never affected the internet connection to the LAN though.

[forkies]

And it has started again...... After a whole week without any problems....The random Internet cutting out is back again.

 

It has happened atleast 5 times today. Random times. Lasts about 3-4 minutes.

Can ping router, but nothing on the Internet. Tracert stops after router.

 

I cant work out what it could be!

 

What firewall do you have? Not a smooth wall by chance?

[Sonic007]

Experienced this at a previous workplace running UniFi AP's (AC-PROs). They were working on a firmware fix for wireless devices not working well with third party DHCP servers which caused the APIPA. As for wired devices, they were unaffected.

 

We use AC Pro access points but this is affecting all machines. Wired or wireless. Everything goes down, including our phones.

 

- - - Updated - - -

 

What are you using as an edge router?

 

Try using an unused Ethernet port, along with a device configured with a static IP ready. This is a simple enough test, which will immediately prove if it's a LAN issue or not.

 

 

We use Schools Broadband so have an Openreach Fibre FSP 150 that then goes into a Mikrotik RB 3011 router. Will give this a go.

Edited December 2, 2021 by Sonic007

[Sonic007]

What firewall do you have? Not a smooth wall by chance?

We use Netsweeper.

[Michael]

So hopefully they'll be a few Ethernet ports on the Mikrotik available which can be re-purposed, ready with a device and a static IP.

 

The important aspect also is to deliberately remove the Ethernet cable plugging into your LAN, so it's completely isolated to just one device.

 

Be interesting to know the results

[Sonic007]

Hi,

So I tried plugging a laptop into another port on the Mikrotik router, setup a static IP. Tried both our normal DNS settings and google 8.8.8.8 DNS settings. Wasnt sure which to put in.

I could ping the router but not anything beyond.

[bald_pig]

Hi,

So I tried plugging a laptop into another port on the Mikrotik router, setup a static IP. Tried both our normal DNS settings and google 8.8.8.8 DNS settings. Wasnt sure which to put in.

I could ping the router but not anything beyond.

 

And the rest of the network was disconnected from the router? Then it's not your network, and it's time to get back on to your ISP!

[Michael]

Hi,

So I tried plugging a laptop into another port on the Mikrotik router, setup a static IP. Tried both our normal DNS settings and google 8.8.8.8 DNS settings. Wasnt sure which to put in.

I could ping the router but not anything beyond.

 

For the purpose of testing, Google DNS is fine, as essentially we want to test anything internet.

 

And the rest of the network was disconnected from the router? Then it's not your network, and it's time to get back on to your ISP!

 

Agreed if everything else was disconnected, it can't possibly be the LAN. You can always try a different cable into the LAN and a different switch port, but then we start to exhaust possibilities.

 

It's also super important to relay this info to your ISP, as it narrows down the possibilities greatly being a local issue.

[ibpalle]

 

We had 4 or 5 WAN IPs and switching between them immediately resolved the issue. Couldn't find any tell-tale IP Location searches on our Smoothwall so never did catch the culprit.

 

 

When you are experiencing issues that could be DOS, it may be an idea to enable auditing in network - settings - advanced - that will record all network traffic going to, through to from the Smoothwall. Otherwise just blocked traffic gets recorded in the firewall logs. Leave the auditing on for an hour or so, then look through the logs.

 

There is an alert for specific port access too that can be set once you find the relevant data - set that up to monitor if the traffic starts picking up again after the initial resolution.

[Davit2005]

Hi,

So I tried plugging a laptop into another port on the Mikrotik router, setup a static IP. Tried both our normal DNS settings and google 8.8.8.8 DNS settings. Wasnt sure which to put in.

I could ping the router but not anything beyond.

 

Do the ISP look after the MikroTik. My experience with MikroTik is limited but you may need to have the port you are connecting to made part of the brdge if that is how they have got the port that connects to your smoothwall set up. MiKroTik are a bit different than your average ISP router which may have multiple LAN ports.

 

I'd ask the ISP to set this up. You could then connect a device to this port and run a few constant pings. One to the WAN port of the MikroTik, one to the WAN connection on your smoothwall and one to a reliable external IP address. Then when the Internet drops out you can compare which one loses connectivity at that time. I'm also assuming you may need to get the smoothwall to allow ping from the device on the WAN port too as ping from the WAN may be disabled by default

Edited December 3, 2021 by Davit2005

[Sonic007]

Do the ISP look after the MikroTik. My experience with MikroTik is limited but you may need to have the port you are connecting to made part of the brdge if that is how they have got the port that connects to your smoothwall set up. MiKroTik are a bit different than your average ISP router which may have multiple LAN ports.

 

I'd ask the ISP to set this up. You could then connect a device to this port and run a few constant pings. One to the WAN port of the MikroTik, one to the WAN connection on your smoothwall and one to a reliable external IP address. Then when the Internet drops out you can compare which one loses connectivity at that time. I'm also assuming you may need to get the smoothwall to allow ping from the device on the WAN port too as ping from the WAN may be disabled by default

 

Thanks for your reply.

We don't use Smoothwall. We have fitering through Netsweeper.

ISP have forwarded it onto higher up at BT so waiting to see what they come back with.

[PaddyNewman]

If it was me at SB, I'd be capturing on the specific proxy you are going through at that point in time, maybe I'm just out of the loop, but Mikrotik are pretty cheap as far as I'm concerned, do they have any other options?

 

Presumably they monitor your edge device? If they see no drops, does it even traverse their WAN. I don't know how they work but as it's Netsweeper and likely WAgent Auth, it's their own MPLS, which is why if they see no drops, I'd be looking at either routing being squiffy or the proxy, I'd be routing you to a specific one and monitoring when you call to say you are down to check you are hitting the bridge at least.

Edited December 3, 2021 by PaddyNewman