Connection issues, DHCP/DNS

[andyhoe]

Hi all, having annoying problems with my Vodafone/Cityfibre connection. When it's working it's generally fine. If it disconnects for whatever reason then I have huge problems trying to reconnect. I just get a red flashing Internet light.

I can spend a couple of hours repeatedly rebooting everything and it might come up again, if it does I then often have DHCP/ DNS issues. I cannot get an address, but if I use a static IP and a public DNS server on my clients they will work. I suspect a router issue, even when I can connect to the router page, none of the settings usually load. Vodafone have logged a ticket with Cityfibre but I'm not convinced it's their issue 

Not sure what to try next! Any ideas?

[CrimsonLiar]

Lol - I was trying to be diplomatic earlier "just in case".

I learnt the hard way don't leave ethernet cables just plugged into the switch at one end and just laying around at the other, someone will come around and plug the other end in too - just to tidy things up - hey presto network storm.

I'd probably be turning off the APs and switches initially to see if that cures the issue, before gradually reintroducing them one by one.  Check cables, dedicated uplink ports, subnets, etc as you go - but you'll know all of this already!

[andyhoe]

Right, so the toaster tripped the power this morning and I'm back with no internet! Rebooted everything around 15 times so far, nothing is connected to the router apart from a laptop. Managed to get a DHCP address once but couldn't ping the router. Added a static IP and can ping the router but cannot web browse to it.

I have tried factory resetting 8 times, 6 of those nothing happened when I pressed the button. The other 2 times, the lights all came on and went out one by one. This doesn't seem to have actually reset anything though as my own SSID is still being broadcast.

Throughout all this the internet light has sat there flashing red 😠 guess I'm back on the phone but it's not really getting me anywhere.

[CrimsonLiar]

Considering your background would it be possible for you to borrow a router from somewhere (never met a network engineer who didn't have an old router or three hanging about somewhere), get your sign-in credentials and give that a go?

[Jayach]

When it all went down, instead trying to get it all back up, start slowly, just a wired device connected to the router after a factory reset. (the lights going out one by one usually signifies it has happened, but the SSID should have reset to default) If you are unable to log in to the router, and browse the settings like that it must be faulty.

[andyhoe]

Well. unbelievably it's all working as it should!

Vodafone support said they'd send a new router, so in the meantime I looked around for spares, only had an expired Meraki unfortunately, also tried a PPPoE connection from my laptop but couldn't get that working. 

I tried one more factory reset and it did something different this time (power light flashing) and actually did factory reset itself. Believe me I must have tried this at least 50 times previously.

So it now connects as it should, 4G backup lights up when WAN disconnects (still can't get online with it but that's another issue to look at) and the phone light is on. I can also get to the web management and everything!

Thanks for everyone's input into this, no idea what caused it but happy to have it working again.

[Jayach]

I wonder if it got a firmware update this time? Don't suppose you made a note of it before?

[network123]

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@Jayach wrote:

It worries me that you can't log into the router. I'm wondering if one the switches is causing some form of network storm and the router is just too busy to service the login.

I know you won't want to touch it just now, but next time you have to reboot disconnect everything from the router except for one device and see if you can connect and use the web interface O.K.

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This is what I'd suggest as well. Does sound like a config gone wrong.

Sounds stupid, but are you running a second DHCP server causing havoc?