Strange Connection Issue

[Eric the Grey]

Last week, we had an outage with our internet (Centurylink).  During the troubleshooting, before the technician found that there was an actual outage in our area, she had me reset my modem to the default (pressing the reset button).  Ever since then, my computer which is one of the three in the house that is hard-wired to the modem, keeps loosing internet access.

 

When this happens, I can still reach the modem interface.  That rules out my onboard NIC.  Wireless devices on the network are all fine.  My work PC, also hard wired to the modem doesn't seem to be affected.  

 

I've checked all the settings I can find in the modem.  Everything is set back to my personal defaults (non-default password, custom network name and password.  

 

The only thing I saw wrong, and this is not always the case, but the modem's build-in diagnostics test shows "DNS #2" as failed.   Right now, it passed.  I'm wondering if this might be the problem, or if it might be something else.  If so, I need to know where to look, because I cannot find anything, and the technician I spoke with came to the conclusion (rightfully so, IMO) that it was a computer issue, since is is only affecting one PC.  

 

I have tried the following:

Spoiler

Rebooted both router and computer.

Release and renewed my network connection.

I attempted to set a static connection, but Windows (10) wouldn't let me save it, and I don't know why, it just would not save.

 

So, where do I go from here?  I know some networking, but not a ton.  More than enough to get myself into trouble, and typically enough to get out of said trouble, but that's about it.  

 

I'm running Windows 10, fully updated

The modem is a Zyxel C3000Z

 

Any suggestions? 

 

 Eric the Grey

[PyCCo_TyPuCTo]

In the ISP modem, change their default DNS IPs to something like 

1.1.1.1 for primary

9.9.9.9 for secondary

 

save, then ipconfig /release and ipconfig /renew on your PC

[Eric the Grey]

9 hours ago, PyCCo_TyPuCTo said:

In the ISP modem, change their default DNS IPs to something like 

1.1.1.1 for primary

9.9.9.9 for secondary

 

save, then ipconfig /release and ipconfig /renew on your PC

 

On this modem, it involves switching from Dynamic DNS to Static in WAN settings if I'm not mistaken. 

 

I tried this and lost internet immediately. Restoring it didn't fix it right away.  Had to wait for my connection to restore.  I did this three times with the same result each time. 

 

Something interesting that I discovered about this modem during my time poking around in it. The box has a Cyber Security mode.  I discovered that turning it OFF (ignoring the vague warning) restores a lost connection.  Turning it back on doesn't automatically cause it to drop again.   

 

I'm turning it off for the day to see if anything changes.  

 

Edit:  Changing the DNS entry did not make a difference on my access when I changed the DNS IPs. 

 

Part of me wonders if it's triggering on my plex server, which runs on my computer since I don't have a server to host it ATM.   

 

 Eric the Grey

[PyCCo_TyPuCTo]

Strange indeed.

Try the ISP Tech Support, they will probably replace the modem.

Don't try and troubleshoot with them, as they are useless. just unplug it, call them, and say your internet isn't working.. 

[PyCCo_TyPuCTo]

16 hours ago, Eric the Grey said:

On this modem, it involves switching from Dynamic DNS to Static in WAN settings if I'm not mistaken.

Why is Dynamic DNS turned on? Is that the default setting? You don't need it unless you're hosting something.

Also, it's either DDNS is ON or it's OFF, it doesn't have a "static mode".

 

I think you may be confusing DNS settings and DDNS settings, those are different things.

You need to configure DNS settings. It's possible you're getting DNS servers from your ISP automatically. That's why I suggested changing them as the ISP DNS sucks and possibly the "DNS #2" has failed out right... Now it doesn't really matter if it's failed, as the #1 is the primary one and your devices will use that one.

 

in Command Prompt on your PC type in "ipconfig /all" and see what DNS servers are configured.

[Eric the Grey]

11 hours ago, PyCCo_TyPuCTo said:

Strange indeed.

Try the ISP Tech Support, they will probably replace the modem.

Don't try and troubleshoot with them, as they are useless. just unplug it, call them, and say your internet isn't working.. 

 

I'm considering that.  I'm wanting to avoid another add-on to my bill, but I think it's the same price.  Gotta check and find out.

 

11 hours ago, PyCCo_TyPuCTo said:

Why is Dynamic DNS turned on? Is that the default setting? You don't need it unless you're hosting something.

Also, it's either DDNS is ON or it's OFF, it doesn't have a "static mode".

 

I think you may be confusing DNS settings and DDNS settings, those are different things.

You need to configure DNS settings. It's possible you're getting DNS servers from your ISP automatically. That's why I suggested changing them as the ISP DNS sucks and possibly the "DNS #2" has failed out right... Now it doesn't really matter if it's failed, as the #1 is the primary one and your devices will use that one.

 

in Command Prompt on your PC type in "ipconfig /all" and see what DNS servers are configured.

 

The DNS server actually says Dynamic or Static, although I am probably looking at the wrong thing, but I don't see anywhere else to change the DNS setting.  The default is ON (see image "DNS" attached).  If I turn it off, it gives me a way to change it (See image "DNS 2" attached) 

 

The only other place I can see is under LAN which only gives me a place to put a server name, and single IP address (See image "DNS Name" attached).  

 

ipconfig /all:

Spoiler

Connection-specific DNS Suffix  . : Home
Description . . . . . . . . . . . : Realtek PCIe GbE Family Controller #3
Physical Address. . . . . . . . . : 18-C0-4D-20-58-4B
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Link-local IPv6 Address . . . . . : fe80::f4a3:d018:e0f1:b063%11(Preferred)
IPv4 Address. . . . . . . . . . . : 192.168.0.3(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Tuesday, March 21, 2023 8:45:15 AM
Lease Expires . . . . . . . . . . : Thursday, March 23, 2023 8:45:16 AM
Default Gateway . . . . . . . . . : 192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
DHCPv6 IAID . . . . . . . . . . . : 202948685
DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-26-71-49-08-18-C0-4D-20-58-4B
DNS Servers . . . . . . . . . . . : 192.168.0.1
                                       205.171.3.25
NetBIOS over Tcpip. . . . . . . . : Enabled

 

 

[PyCCo_TyPuCTo]

Yeah, their GUI is confusing...

There is a Tab called "Dynamic DNS" just under "WAN Settings" in the top left corner. That's the stuff that usually is OFF by default, unless you need it.

 

The DNS settings are in your second picture, change those two IPs from 205.171.3.25 and 205.171.2.25 to something like 1.1.1.1 and 9.9.9.9 and save it. 

 

Your third picture, under "LAN settings" leave those alone (disabled)

 

 

Now for the PC, it's getting it's IP automatically, so after you change your DNS IP on your router, issue "ipconfig /release" and "ipconfig /renew" on your PC...

 

then your DNS settings should change and you should no longer use the ISP DNS

Might need a reboot.

[Eric the Grey]

58 minutes ago, PyCCo_TyPuCTo said:

Now for the PC, it's getting it's IP automatically, so after you change your DNS IP on your router, issue "ipconfig /release" and "ipconfig /renew" on your PC...

 

then your DNS settings should change and you should no longer use the ISP DNS

Might need a reboot.

I actually did that earlier (see above) and lost the ability to reach the internet at all.  I just switched it again, and re-enabled the cyber security as a test. For the moment it's good.  Like I said, it's flaky.  It comes and goes.

 

My question is, changing my DNS, who am I getting to sites on the internet?  Don't I need an actual DNS server?  My computer now shows the following. Just my router's internal IP, and no secondary. 

 

   DNS Servers . . . . . . . . . . . : 192.168.0.1
 

So what is doing my translation?  

 

 

[PyCCo_TyPuCTo]

The router is supposed to advertise via DHCP whatever DNS server you statically assign, in fact both of them.

Your PC is not receiving those servers, so it's using it's default gateway as DNS, since there are no other options.

You should still be good as your router still has DNS servers configured. 

 

Look at your DHCP settings, something may be broken there.

[Eric the Grey]

3 hours ago, PyCCo_TyPuCTo said:

The router is supposed to advertise via DHCP whatever DNS server you statically assign, in fact both of them.

Your PC is not receiving those servers, so it's using it's default gateway as DNS, since there are no other options.

You should still be good as your router still has DNS servers configured. 

 

Look at your DHCP settings, something may be broken there.

 

According to my DHCP page, I get what is shows below.  If I change from Default Servers to Manual Servers, it has the second screenshot.  Basically what I set as the primary DNS Type in the WAN Settings.  Everything else looks OK to me.  

 

[PyCCo_TyPuCTo]

OK, that explains it.

Change Primary DNS to 1.1.1.1

and Secondary to whatever else like 9.9.9.9 or 8.8.8.8 etc.

There is no need for your router to be your primary DNS server as it simply isn't one. It's not capable of resolving anything, it will forward DNS request further according to its' own DNS settings, so it's a useless messenger in the middle.

[Falcon1986]

@Eric the Grey

 

After you change the DNS on the gateway, all currently-connected clients must disconnect and reconnect or else they're using the old DNS information.

[Eric the Grey]

13 hours ago, PyCCo_TyPuCTo said:

OK, that explains it.

Change Primary DNS to 1.1.1.1

and Secondary to whatever else like 9.9.9.9 or 8.8.8.8 etc.

There is no need for your router to be your primary DNS server as it simply isn't one. It's not capable of resolving anything, it will forward DNS request further according to its' own DNS settings, so it's a useless messenger in the middle.

 

Should I reset the WAN DNS connection back to the default (dynamic)?  I think the 1.1.1.1 in the latest screenshot is being picked up from there.

 

3 hours ago, Falcon1986 said:

@Eric the Grey

 

After you change the DNS on the gateway, all currently-connected clients must disconnect and reconnect or else they're using the old DNS information.

I always do a ipconfig /release and ipconfig /renew.   I've also done /flushdns a few times as well.

 

[PyCCo_TyPuCTo]

5 hours ago, Eric the Grey said:

Should I reset the WAN DNS connection back to the default (dynamic)?  I think the 1.1.1.1 in the latest screenshot is being picked up from there.

No, keep both WAN and LAN(DHCP) DNS settings the same.

[The 8-Bit Time Traveller]

On 3/23/2023 at 7:36 AM, PyCCo_TyPuCTo said:

OK, that explains it.

Change Primary DNS to 1.1.1.1

and Secondary to whatever else like 9.9.9.9 or 8.8.8.8 etc.

There is no need for your router to be your primary DNS server as it simply isn't one. It's not capable of resolving anything, it will forward DNS request further according to its' own DNS settings, so it's a useless messenger in the middle.

 

It's always DNS

 

It's a good catch, while most routers are able to act as DNS caches and relays, it can cause issues. By making the primary DNS 1.1.1.1 you are taking the router out of the loop as far as DNS resolution is concerned. Try it and let us know if it helps.

 

To confirm DNS issues, you can do the following

During an outage, open up command prompt and do the following

 

type: ping 1.1.1.1

if it looks like this:

It means that your internet is working, and it is likely DNS

 

type: ping www.google.com

if you get an error about the host name, you know DNS is not working

 

[Eric the Grey]

52 minutes ago, The 8-Bit Time Traveller said:

 

It's always DNS

 

It's a good catch, while most routers are able to act as DNS caches and relays, it can cause issues. By making the primary DNS 1.1.1.1 you are taking the router out of the loop as far as DNS resolution is concerned. Try it and let us know if it helps.

 

To confirm DNS issues, you can do the following

During an outage, open up command prompt and do the following

 

type: ping 1.1.1.1

if it looks like this:

It means that your internet is working, and it is likely DNS

 

type: ping www.google.com

if you get an error about the host name, you know DNS is not working

 

 

I was able to ping outside sites (I tend to ping out Webex server, since I do that at work a lot, it has become habit) but I had not tried 1.1.1.1.  Of course, it works.

 

The only other thing I did was I left the cyber security off.  Playing around with it on and off, I've found it tends to block sites I want to go to, and ones I know are safe.   Centurylink has put in their own filters that I don't agree with.  I'm careful enough to not get caught, at least no so far.

 

I'm calling this resolved and have marked it so.  Thanks to everyone who helped.  

 

 Eric the Grey

[The 8-Bit Time Traveller]

53 minutes ago, Eric the Grey said:

 

I was able to ping outside sites (I tend to ping out Webex server, since I do that at work a lot, it has become habit) but I had not tried 1.1.1.1.  Of course, it works.

 

The only other thing I did was I left the cyber security off.  Playing around with it on and off, I've found it tends to block sites I want to go to, and ones I know are safe.   Centurylink has put in their own filters that I don't agree with.  I'm careful enough to not get caught, at least no so far.

 

I'm calling this resolved and have marked it so.  Thanks to everyone who helped.  

 

 Eric the Grey

Awesome, I'm glad it worked!