dns problem

[Sean Nelson]

ac68u running 380.69_2 (planning to move to 384 but needs time to do the re-configuration so ...)

I have been having this problem for a long time, with earlier versions as well --

After the router has been up for a while (a couple of days? the length of the period seems random), it will stop serving new DNS queries. My computers will continue to access cached addresses, but new query will hang (browser hanging on "looking up foo.com ..." and eventually timing out).

The only reliable cure is hard reset (as in disconnecting and reconnecting power supply -- soft reboot does not always work).

This happens whether default DNS servers are used (with DNS fields left empty) or specific DNS servers are given (e.g. Google, OpenDNS, etc.).

Is this a known issue? Is there a solution?

thanks,

Sean

 

[ThanksForThis]

Are you running Privoxy with a scheduled filter update?
Do you have optware/entware that integrates with Dnsmasq in any way? Additionally, if so, do you have a scheduled usb disk check?
Are you able to access the router via the webui while this is occuring?
Does the system log > general log provide any insight into dhcp or dnsmasq errors?
Are you able to establish an SSH connection during this time?

If you don't know some of what I'm asking about, feel free to ask for further elaboration.

 

[Sean Nelson]

Are you running Privoxy with a scheduled filter update?
Do you have optware/entware that integrates with Dnsmasq in any way? Additionally, if so, do you have a scheduled usb disk check?
Are you able to access the router via the webui while this is occuring?
Does the system log > general log provide any insight into dhcp or dnsmasq errors?
Are you able to establish an SSH connection during this time?

If you don't know some of what I'm asking about, feel free to ask for further elaboration.

No Privoxy, No optware/entware, router accessible while dns is down, nothing regarding dns in log, ssh to router possible.

I could also access anything via numerical ip. In all appearance DNS seems the only problem. Often times I wouldn't even notice this (as I usually work through established connections ) until someone else in the household told me.

I usually use pass-thru DNS (i.e. empty DNS spec in config). Since restarting router (without doing anything to modem) fixes the problem I suppose it has nothing to do with the modem. But in any case the modem is a Zyxel Q100.

Thanks,

Sean

 

[Sean Nelson]

dns settings (under LAN->DHCP Server)

I have a DSL modem connecting to outside that runs DHCP service and assigns 192.168.0.1 to itself and 192.168.0.2 to my router which is the only client connected to the modem. The router then runs DHCP services and assigns 192.168.1.1 to self and the real clients to 192.168.1.x (some are manual, e.g. printer, most are dynamic).

So I suppose my AC68U sees WAN address as 192.168.0.2 and gateway 192.168.0.1 (I suppose the WAN DNS is also 192.168.0.1, through the modem). Normally, my computers see as gateway (and DNS) as 192.168.1.1. A DNS query from my computer goes to the router at 192.168.1.1, which forwards it to the modem at 192.168.0.1, which has real DNS servers configured and will make the query and get the answer; it then sends it back to the router, which sends it back to my computer. If I put e.g. 8.8.8.8 into the (empty) slot for DNS in the attached pic, then router would forward query to 8.8.8.8 directly instead of 192.168.0.1. Correct?

Sean

 

[ColinTaylor]

So I suppose my AC68U sees WAN address as 192.168.0.2 and gateway 192.168.0.1 (I suppose the WAN DNS is also 192.168.0.1, through the modem).

You can check the current addresses on the Network Map page, click the globe icon.

If I put e.g. 8.8.8.8 into the (empty) slot for DNS in the attached pic, then router would forward query to 8.8.8.8 directly instead of 192.168.0.1. Correct?

No. That address will be sent to DHCP clients and the clients themselves will query 8.8.8.8 directly. What you probably want to do is put your preferred DNS server addresses in WAN > Internet Connection > WAN DNS Setting (after setting Connect to DNS Server automatically to No).

 

[Sean Nelson]

You can check the current addresses on the Network Map page, click the globe icon.

No. That address will be sent to DHCP clients and the clients themselves will query 8.8.8.8 directly. What you probably want to do is put your preferred DNS server addresses in WAN > Internet Connection > WAN DNS Setting (after setting Connect to DNS Server automatically to No).

That makes sense. Silly me I never looked under WAN ... So what is the purpose of the DMS server setting under LAN?

Or maybe you meant that the DNS setting under LAN is sent to client to query, while the one under WAN is used by the router itself to query (when serving as DNS server for the client)?

Thanks!

Sean

 

[ColinTaylor]

Or maybe you meant that the DNS setting under LAN is sent to client to query, while the one under WAN is used by the router itself to query (when serving as DNS server for the client)?

Yes.

 

[JWolf]

I am having this exact issue but with an AC-86U running 384.3. I installed and configured it just about a month ago and within the last week I started getting random internet drops, specifically with named based services. Those that are IP based still continue to work while using named URL's fails with an IP address not found for the address. During this 'outage' the router is fully accessible and the WAN connectivity light is lit up with a good status. I am able to restore functionality by powering it off an back on, via the power button, no hard disconnect required. I can also get it to recover about 50% of the time by rebooting it from the GUI. Sometimes it also just resolves itself after about 30 minutes or so.

I have tried switching to google's DNS servers and as in the default passthrough configuration, it works for a time but eventually starts failing as well.

At first I was inclined to blame Comcast for this but it is beginning to sound like it might be a firmware issue. I have the configuration fully backed up and am probably going to try a factory reset with a restore from backup to see if it has an effect. If it comes back I am not sure what to try next.

Any insight or guidance here would be very helpful.

 

[Sean Nelson]

Updated to 384.4 ... It seems the issue remains. It must have something to do with the settings, if not everyone has the problem.

 

[JWolf]

FWIW, a factory reset of the 384 config and restoring from backup config did not resolve the issue.

I'm wondering what specific settings could be the cause here.

Maybe we can compare settings and see if there's a common thread.

An overview of 'non standard' settings in my configuration:

Guest network enabled on 2.4ghz radio

Statically assigned IP's to all of the devices on my network. DHCP pool allows for 5 additional IP's for guest network access.

Mac address filtering is enabled and configured for both radios

DDNS configuration is enabled and working

Firewall is enabled, I wonder if this is bad or has an impact. I've read to disable it but I turn off the Windows firewall and don't want to run unprotected.

Otherwise the rest of the settings are default.

 

[Sinner]

on the wan tab if you set:
Connect to DNS Server automatically (No )
DNS Server1 x.x.x.x
DNS Server2 x.x.x.x

where x is your dns servers of choice, can even match whats in your actual modem or the google ones it will work. if your still losing connections its prolly not dns related. you can be sure of this by watching Netflix for example. if you halfway thru a movie and it drop its not dns because it already knows where the movie is coming from and doesn't need to look it up until possibly the next movie. might be something else

 

[JWolf]

on the wan tab if you set:
Connect to DNS Server automatically (No )
DNS Server1 x.x.x.x
DNS Server2 x.x.x.x

where x is your dns servers of choice, can even match whats in your actual modem or the google ones it will work. if your still losing connections its prolly not dns related. you can be sure of this by watching Netflix for example. if you halfway thru a movie and it drop its not dns because it already knows where the movie is coming from and doesn't need to look it up until possibly the next movie. might be something else

I have tried alternate DNS servers and the same issue occurs. I can confirm your statement that it is not DNS due to the fact that I don't lose connection to in process streaming and or multiplayer gaming sessions when this is happening. However if I reload the stream or disconnect and attempt to reconnect, I am unable to. This would confirm that it's DNS related.