Maximum number of concurrent DNS queries reached (max: 150)

[bbq]

My Asus router occasionally appears to lock up and I don't know what to do about it. It doesn't work again until I power-cycle it. I'd appreciate any guidance to make it more robust.

Environment:
Router 1: Asus RT-AC68U running Merlin v386.13
- no add-ons, except apparently scMerlin - I don't recall installing that.
Router 2: AiMesh with another Asus RT-AC68U running Merlin v386.13 with a hardwire CAT5-e connecting it to the first router
ISP: T-Mobile Home Internet 5G, usually good or excellent strength signal. T-Mobile use CG-NAT
- router 1 is connected to the T-Mobile gateway with CAT5E cable. Not using bridge-mode, so there would be double NAT.
Usually about 30 client on the network, many wired, but some are not
- includes computers, laptops, HDHomeRun Connect Quatro, google home and Amazon echo device, chromecast devices, fireTV, android phones, Meross smart garage, Kasa smart outlets, etc

For no apparent reason, all Wifi and ethernet activity will stop both to the internet and within my home internet. Even with a hardwire connection, I am unable to connect to the Asus admin page of the router, nor to admin pages of other equipment including the modem/gateway.
The T-Mobile Modem/Gateway has WiFi of its own, and sometimes (but not always), I am able to have a laptop connect to that WiFi and use the internet even while my home intranet/router is down.

I have attached the system log from the router after this happened and the router was power-cycled. I think re-booting starts at line 5489 when the date changes from Aug 17 to May 5. The most recent errors are:
- Maximum number of concurrent DNS queries reached (max: 150) - this is repeated several times.

There are another set of errors, but I don't think this is the problem:
- kernel: 50:1E:2D:09:9E:CE not mesh client, can't delete it
The MAC address is for a older Dell laptop running Windows 10, but there are others like it for a Motorola android phone, a Facebook Portal, and a Panasonic TV. I don't know that that means, not how to correct it, but I don't think that is the problem.

My theory of what is going on is that the ISP has a disruption to service that drops the internet for a while. It may come back, allowing me to connect directly to the T-Mobile Gateway WiFi, but the Asus router doesn't recover. I don't mind the occasional drop in the internet, but I'd really like the things in my home to continue to operate at least within the home, especially since my my TV antenna uses my intranet. I think when the internet dies, something starts issuing a lot of DNS queries which maxes out some list on the router, which then is the end for the router.

Is there anything I can do about this? Can I run some Merlin add-ons to service these DNS queries locally? Is there some setting to look at?

Thanks for any help.

 

[ColinTaylor]

That error usually means that your upstream DNS server isn't responding. The errors should clear once the DNS service is restored.

 

[bbq]

That error usually means that your upstream DNS server isn't responding. The errors should clear once the DNS service is restored.

Sure. That is easy to believe, but then explain:
1) The router continues to be non-operational until unplugged and plugged in again. What happened when I rebooted my router that made the upstream DNS server work again?
2) Why does a failure in the upstream DNS server affect the a computer from accessing another computer in my home by using the IP address like 192.168.1.200. Why would the upstream DNS server be queried for that?

 

[fromdetroit]

My Asus router occasionally appears to lock up and I don't know what to do about it. It doesn't work again until I power-cycle it. I'd appreciate any guidance to make it more robust.

Environment:
Router 1: Asus RT-AC68U running Merlin v386.13
- no add-ons, except apparently scMerlin - I don't recall installing that.
Router 2: AiMesh with another Asus RT-AC68U running Merlin v386.13 with a hardwire CAT5-e connecting it to the first router
ISP: T-Mobile Home Internet 5G, usually good or excellent strength signal. T-Mobile use CG-NAT
- router 1 is connected to the T-Mobile gateway with CAT5E cable. Not using bridge-mode, so there would be double NAT.
Usually about 30 client on the network, many wired, but some are not
- includes computers, laptops, HDHomeRun Connect Quatro, google home and Amazon echo device, chromecast devices, fireTV, android phones, Meross smart garage, Kasa smart outlets, etc

For no apparent reason, all Wifi and ethernet activity will stop both to the internet and within my home internet. Even with a hardwire connection, I am unable to connect to the Asus admin page of the router, nor to admin pages of other equipment including the modem/gateway.
The T-Mobile Modem/Gateway has WiFi of its own, and sometimes (but not always), I am able to have a laptop connect to that WiFi and use the internet even while my home intranet/router is down.

I have attached the system log from the router after this happened and the router was power-cycled. I think re-booting starts at line 5489 when the date changes from Aug 17 to May 5. The most recent errors are:
- Maximum number of concurrent DNS queries reached (max: 150) - this is repeated several times.

There are another set of errors, but I don't think this is the problem:
- kernel: 50:1E:2D:09:9E:CE not mesh client, can't delete it
The MAC address is for a older Dell laptop running Windows 10, but there are others like it for a Motorola android phone, a Facebook Portal, and a Panasonic TV. I don't know that that means, not how to correct it, but I don't think that is the problem.

My theory of what is going on is that the ISP has a disruption to service that drops the internet for a while. It may come back, allowing me to connect directly to the T-Mobile Gateway WiFi, but the Asus router doesn't recover. I don't mind the occasional drop in the internet, but I'd really like the things in my home to continue to operate at least within the home, especially since my my TV antenna uses my intranet. I think when the internet dies, something starts issuing a lot of DNS queries which maxes out some list on the router, which then is the end for the router.

Is there anything I can do about this? Can I run some Merlin add-ons to service these DNS queries locally? Is there some setting to look at?

Thanks for any help.

It's difficult to diagnose your exact issue but it seems you don't have a DNS issue, you have a routing/DHCP issue. The fact your ISP uses CG-NAT makes it a little more complicated on your end. I also have a feeling DHCP is active on both the TMO modem and a router(s). I'm not familiar with TMO's CG-NAT config, but the probably the easiest and least stressful way to fix is to call TMO and have them walk you through setting up your internal network to connect with CG-NAT.

 

[sfx2000]

ISP: T-Mobile Home Internet 5G, usually good or excellent strength signal. T-Mobile use CG-NAT
- router 1 is connected to the T-Mobile gateway with CAT5E cable. Not using bridge-mode, so there would be double NAT.

T-Mobile Home Internet is not CGNAT - it's 464-XLAT

Might not be a popular thought here - but just use their GW and be done with it...

 

[heysoundude]

Frankly, your entire network could probably benefit from an objective reevaluation and redesign based on how you would like to use it.

T-Mobile is your ISP, and it’s a 5G cellular modem/gateway router you have? If so, I’m in agreement with @sfx2000 and say turn your Asus hardware into APs (if necessary for wireless coverage in your home): the T-Mobile hardware is (likely, presumably) more modern and capable than your Asus hardware. I’d even go so far as to recommend turning off 2.4GHz radios where possible, but it seems you’ve quite a bit of IoT stuff that might stop working if you do…and speaking of which, a lot of that IoT stuff “phones home” and increases traffic on both the LAN as well as the WAN connection, and your LAN side is already plenty busy with 4 TV channels streaming through it.
I’d definitely suggest looking into some basic network segmentation, which may help with not overloading your router. I’m not a pro, so I can’t say whether subnetting or vLANs are the way to go for you (or if both are likely necessary in your situation, if that’s even possible…)