Ping lost when reboot AC68U main/node

[DummyPLUG]

First of all thanks very much to ASUS tech support which try to help me to solve the problem in the past few months

I had a ping lost problem when I reboot the main/node, I have this problem a long time and today ASUS support said they still can't find the reason, so I am here to see if someone can reproduce my problem.

I use my AC68u as AP, with 2 more AC68U as node, they are using ethernet as backhaul, when I reboot the main/node, doesn't matter only one of them or all of them, my PC which is not connect to any AC68U will have ping lost, the more the node reboot, the longer and easier the ping lost happen.

As it seems this is a rare case and ASUS told me they can only reproduce this problem once

If you have time please do me a favor to have a test, make sure you have flow control turn on, as with flow control turn off there will not have any ping lost:
1. keeps ping www.google.com
2. keeps ping the all asus router(both the main and the node)
3. telnet into the node and reboot them
4. if you see ping lost to www.google.com before the node finish reboot, that means you have the same problem with me, normally you should not see any ping lost.
p.s. sometime it will also have ping lost if reboot the main instead of the node

I had attach my network diagram for anyone interested.

 

[ColinTaylor]

From what you've described this doesn't sound like it's a problem with the Asus', but rather the behaviour of the switches (Cisco and/or Draytek) and flow control.

I'd guess it happens because when one of the Asus' is rebooted the link speed to the switch changes causing flow control to kick in.

https://www.smallnetbuilder.com/lanwan/lanwan-features/30212-when-flow-control-is-not-a-good-thing

 

[DummyPLUG]

From what you've described this doesn't sound like it's a problem with the Asus', but rather the behaviour of the switches (Cisco and/or Draytek) and flow control.

I'd guess it happens because when one of the Asus' is rebooted the link speed to the switch changes causing flow control to kick in.

https://www.smallnetbuilder.com/lanwan/lanwan-features/30212-when-flow-control-is-not-a-good-thing

Yes it is related to flow control, and the problem is the ac68u generate too much pause frame which cause the problem, and when reboot the ac68u generate 1000+ pause frame within 2~3 second in my case. I don't have this problem with AP from other manufacturer. We found it may related to the ac68u's lldpd, but Asus's engineer still can't find the root cause.

Asus said they can only reproduce it once and don't have report from others, may be I am the only unlucky one.

Currently I had disable flow control on those port connect to AC68U, but this also generate some side effect for some of my program, so in long term either there is a solution or I had to replace all ac68u