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]

Okay, so I guess the lack of replies to your query is because it's quite odd!  Generally, your router not being able to get internet access shouldn't stop clients from reviving local DHCP info - including DNS addresses (even if they're not available due to the internet being down).

Can we assume that your setup is pretty standard :

ONT/PON > Router > LAN & WIFI clients

If there is any other network infrastructure or connections (including to telephone sockets) in there could you let us know what, and how it is connected!

*Query:  Does the current Vodafone router work as a caching DNS server, pushing its own address (192.168.1.1 or similar) out to clients, or does it direct clients to DNS servers directly?

[Jayach]

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@CrimsonLiar wrote:

*Query:  Does the current Vodafone router work as a caching DNS server, pushing its own address (192.168.1.1 or similar) out to clients, or does it direct clients to DNS servers directly?

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Caching:

 

 

[andyhoe]

Thanks for the reply.

It is fairly standard and as you described. The only other things on the network are one dumb switch, one managed switch and three wired APs.

The only changes I've made to the router config are WiFi details and a few IP reservations.

Service is currently working although I cannot get to the router config page via a browser (doesn't even time out, just keeps on with the spinning wheel) and the Vodafone app says "App to router connection failed"

Wireshark shows my computer hitting the router IP and getting ACKs but I don't know enough what it should look like to know the difference.

Regarding your DNS query, it uses itself - 192.168.0.1

[network123]

In addition to above, what software version is your router?

[andyhoe]

At the moment I have no access to the router page so cannot tell unfortunately!

I'm loathed to reboot it as yesterday I spent probably 4-5 hours rebooting to get it to how it is now - a semi-working service, also while on the phone or in a chat to Vodafone support. Once the service is sort of working though, they lose interest and close the ticket.

[Jayach]

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.

If would also probably be a good idea to back up your configuration and do a factory reset to clear everything down.

If with just one device you are unable to use the web interface O.K., it sounds like a faulty router.

[andyhoe]

Agreed but there certainly don't seem to be excessive broadcasts when packet sniffing. Every time I reboot, I do take everything out but seems to make no difference.

Also the 4G backup will never kick in. When I tell support they ask me to reboot my router to test but I don't want to do that! The dongle works fine in a laptop, I believe there is a router issue but can't seem to convince anyone in support.

My job is as a network manager and if this happened to one of my devices there I would have easily got a replacement by now!

Next time I can get to the web interface I'll definitely try to factory reset 👍

[network123]

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@andyhoe wrote:

Also the 4G backup will never kick in. When I tell support they ask me to reboot my router to test but I don't want to do that! The dongle works fine in a laptop, I believe there is a router issue but can't seem to convince anyone in support.

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Oh wow, I didn't even know this would work lol. I would say does it say your connected to mobile signal on the router settings, but... awkward.

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@andyhoe wrote:

Next time I can get to the web interface I'll definitely try to factory reset 👍

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I think there's a button at the back you can press IIRC.

[Jayach]

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@network123 wrote:

I think there's a button at the back you can press IIRC.

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Yes, hold it in for at least 10 seconds.