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RT-AC88U Packet Loss and High Latency

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sbsnb

Very Senior Member
I have an RT-AC88U running Merlin 380.68_4 and I'm experiencing up to 15% packet loss and latency as high as 500ms pinging the router from wireless clients on the LAN. This wasn't happening for the past couple of months, but started in the last week or two. I've tried every single channel, 20 MHz channel, 40 MHz channel, 20/40MHz channel. The CPU load on the dashboard is always between 0 and 1% and the bandwidth being used at any given time during testing is nearly 0. I tried rebooting the router and the wireless clients. Nothing seems to make any difference. The system logs don't suggest anything out of the ordinary. Temperatures are fine.

I had a previous RT-AC88U that had the 2.4GHz radio fail after 32 days and this is the replacement. I'm starting to wonder if this radio is now failing.
 
Wireless survey at the RT-AC88U.

YWcGnHD.png


Channel 8 is the RT-AC88U.
 
Also tried turning off QoS in case that was causing issues. No help there either.
 
Verified that the problem does not exist for wired clients.
 
Your channel 8 is interfering with two other APs there with partial overlaps. I recommend using channel 11 instead - if you're going to overlap, it's better to overlap on the exact same channel than halfway.
 
Your channel 8 is interfering with two other APs there with partial overlaps. I recommend using channel 11 instead - if you're going to overlap, it's better to overlap on the exact same channel than halfway.

Thanks for responding. I'm interested in the details of this. In the HAM radio world, it is better that overlap at the "edges" of the signal than directly overlap because the larger the signal-to-noise ratio, the better the radio can reject interference. I guess to simplify it a little bit you could say that it's best to maximize the area under the sine wave that is not overlapping another.

Perhaps the difference lies in how 802.11 protocols work?
 
After upgrading to 382.1_2 and switching to channel 11:

Ping statistics for 192.168.1.1:
Packets: Sent = 41, Received = 32, Lost = 9 (21% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 1546ms, Average = 157ms
 
Perhaps the difference lies in how 802.11 protocols work?

I don't know the exact technical details, but from what I gathered, 802.11 will have APs ensure that there isn't another transmission already occurring before using a channel. If you're on the same channel, then this will work as intended. However if you're not exactly on the same channel, it will be seen as just random noise by your AP, preventing it from intelligently handling it, and it might just try to transmit "through the noise then".

Think of it a bit as intelligent collision detection/prevention.

Again, this is just what I've read, and I might not be 100% correct.

Packets: Sent = 41, Received = 32, Lost = 9 (21% loss),

All I can think then is either you are in a very noisy environment (keep in mind the 2.4 GHz band is used by a lot of devices, not just 802.11 wifi), or one of your clients is saturating the channel with traffic. Try doing the ping test with only one client connected to your network. If it's more stable, start connecting others one at a time. Sometimes, it's a client that does a lot of network traffic (broadcasts, malware, backups, etc...). Sometimes, it's a defective client that has a failing network interface, flooding the connection with noise. I've had a similar issue once with a customer, the network NIC of one of their computers was causing random packet losses for everyone else just like you. Replacing that computer's NIC resolved the issue.
 
Did you got any luck fixing this problem?
I've been experiencing this for a long time, upgraded firmware to 384.8_2 but from time to time spikes in ping responses from router and packets loss happen for wireless clients.
 
Last edited:
I haven't had any issues like this for some time, but I'm not sure what I did to resolve it. All of the advanced wireless settings are still at default, so it's probably not something obvious.
 

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