Intermittent issues with DNS proxy

[htismaqe]

I just got my router up and running today (latest RMerlin FW) and I'm having intermittent issues with name lookups failing.

The router is using my ISP DNS servers. DHCP was originally setup to pass the router's address to DHCP clients for DNS lookups.

Every so often, a lookup fails. For example, I couldn't open www.speakeasy.net in my browser and attempt to ping from CLI would result in an "unresolved hostname" error.

However, in another terminal session on the same machine, I can ping www.speakeasy.net by IP address and I can also ping it from the router management page itself.

Changing my DHCP settings to pass my ISP DNS server address to the DHCP client fixes the issue immediately.

 

[htismaqe]

Or maybe not.

Just now it wouldn't resolve forums.smallnetbuilder.com. It resolved other queries at the same time, so it's like individual requests/packets are being lost.

 

[htismaqe]

I noticed quite a few people here enabling QoS and putting DNS as highest priority.

I went ahead and set that up.

I haven't seen the issue since but it's only been an hour or so...

 

[htismaqe]

So today, all of the sudden, I started getting massive packet loss on every wireless segment, including the APs that are connected to the router via switch ports.

I disabled QoS and the problem seems to be fixed.

Are these common issues with the RMerlin firmware?

 

[L&LD]

You don't state the router, the firmware ('latest' is not descriptive enough) or any settings you may have changed from defaults, nor any extra features, devices, or customized scripts you may be using with the router either.

Hard to offer help.

 

[htismaqe]

It's a RT-N66W running RMerlin 3.0.0.4.374.39.

Using the 2.4Ghz radio. 5Ghz radio is off.

Wireless Mode: Legacy
Optimized for Xbox and B/G Protection unchecked.
Wireless Mode Optimized for Xbox b/g Protection
Channel bandwidth: 20Mhz
Control Channel:11
WPA2-PSK, AES

I live in a rural area, closest neighbor is a couple miles away.

As stated originally, the problem first manifested itself with QoS off, using the router's address as the DNS server for DHCP clients. I manually changed the DNS server in the router config so that it would pass my ISP's primary NS to the clients. That resolved the problem temporarily. It started happening again, so I enabled QoS.

QoS settings:

DNS 53 tcp/udp Highest
time 37 tcp/udp Highest
NTP 123 tcp/udp Highest
RSVP 3455 tcp/udp Highest

I also had my work IP phone set to Highest via MAC address.

Today, things got really slow and that's when I noticed packet loss trying to load various webpages on the Internet.

I have a workstation connected to the guest network on the Asus router. It showed packet loss pinging the local LAN interface of the router.

I have a workstation connected to an AP that is connected to the Asus router via one of the ethernet ports. It too show packet loss ping the local LAN interface of the router.

Wireless signal strengths did not fluctuate wildly during the event, so it suggests to me the router itself, not the wireless links, as the culprit.

Disabling QoS altogether seems to have fixed the problem. I have not tried re-enabling DNS proxy since it was working using hardcoded DNS name server.

 

[L&LD]

Wireless mode, 'Legacy'. Why?

 

[htismaqe]

Wireless mode, 'Legacy'. Why?

Doesn't that just fix the maximum link rate at 54Mbps? I don't have anything but G clients.

EDIT: I had my old WNDR3700 setup the same way.

 

[L&LD]

Yes, it does fix the max link rate to 54Mbps, but I don't think that is 'all' it does.

I would test with Wireless mode to 'Auto' (I would also reboot after changing that setting) and see if the QoS works then.

If all you are connecting is G clients, then leaving the router to Auto should give you the best performance possible (including taking advantage of hidden parameters that the router may enable, even for G clients).

 

[htismaqe]

OK, sounds good. I'll give it a try.

EDIT: would you also re-enable DNS proxy or does it really matter? dnsmasq on my old 3700 wasn't the most reliable...

 

[htismaqe]

As I'm sitting here getting ready to change the setting, the packet loss is back.

I don't think the Legacy setting is the culprit because I'm seeing packet loss on my Mac, which is connected to an AP. It's connection to the router is via a switch port.

 

[L&LD]

Okay, sorry I can't help more.

 

[htismaqe]

I guess what I'm wondering is whether or not other users have experienced issues with:

1) DNS proxy and
2) QoS

I'm looking for "best practice" when it comes to these 2 things.

Right now, I'll just leave them both off. If the packet loss continues, I'll reset to defaults and re-flash.