AX86U LAN Keeps Dropping

[BaronBerserker]

Hello,

I've tried Asus support without much luck, so I'm hoping someone here can help. I have a new AX86U where initially, the only change I made was updating the firmware right away. However, the LAN connection to my PC started dropping for about 30 seconds at apparently random times - sometimes I'll go a whole day without any issues; earlier this afternoon, it dropped six times in 10 minutes. It always reconnects automatically. WiFi hasn't had any issues so far.

Everything works great with all of the same components but swapping back to my older Asus router, so I assume the issue must be with the AX86U. I've tried two of the four LAN ports on the back, and both show this issue.

Just as a guess, I tried extending the DHCP lease time as far as it will go. The DHCP query frequency was originally set to Agressive Mode, but I've tried both Normal Mode and Continuous Mode as well, with no luck. Asus support also had me try enabling the "Jumbo Frame" option under Advanced Settings > LAN > Switch Control.

Around the time the connection drops, I frequently see repeating message combinations like this in the system logs:

Jan 7 19:35:02 kernel: eth1 (Ext switch port: 0) (Logical Port: 8) (phyId: 8) Link DOWN.
Jan 7 19:35:02 kernel: br0: port 4(eth1) entered disabled state
Jan 7 19:35:22 kernel: eth1 (Ext switch port: 0) (Logical Port: 8) (phyId: 8) Link Up at 100 mbps full duplex
Jan 7 19:35:22 kernel: br0: port 4(eth1) entered listening state
Jan 7 19:35:22 kernel: br0: port 4(eth1) entered listening state
Jan 7 19:35:24 kernel: br0: port 4(eth1) entered learning state
Jan 7 19:35:26 kernel: br0: topology change detected, propagating
Jan 7 19:35:26 kernel: br0: port 4(eth1) entered forwarding state
Jan 7 13:35:30 dnsmasq-dhcp[26933]: DHCPDISCOVER(br0) [PC IP address] [PC MAC address]
Jan 7 13:35:30 dnsmasq-dhcp[26933]: DHCPOFFER(br0) [PC IP address] [PC MAC address]
Jan 7 13:35:30 dnsmasq-dhcp[26933]: DHCPREQUEST(br0) [PC IP address] [PC MAC address]
Jan 7 13:35:30 dnsmasq-dhcp[26933]: DHCPACK(br0) [PC IP address] [PC MAC address]

And then all that repeats again the next time it goes down and comes back up. I'm also not sure why the time codes seem to change so drastically - with the next LAN drop, the first section is back around 19:35 before switching back to 13:35 again toward the end.

I'm not sure if it's related, but I also see a fair number of repeated messages like this:

Jan 7 13:33:59 acsd: acs_candidate_score_intf(1133): eth7: intf check failed for chanspec: 0xe832 (36/160)
Jan 7 13:33:59 acsd: acs_candidate_score_bgnoise(1602): eth7: bgnoise check failed for chanspec: 0xe832 (36/160)
Jan 7 13:33:59 acsd: acs_candidate_score_txop(1860): eth7: txop check failed for chanspec: 0xe832 (36/160)
Jan 7 13:34:00 acsd: acs_candidate_score_intf(1133): eth7: intf check failed for chanspec: 0xe932 (40/160)

Any thoughts or other things I can try? I'd prefer sticking with stock firmware instead of trying Merlin just yet, if possible.

 

[L&LD]

Welcome to the forums @BaronBerserker.

Try different Ethernet cables. Different brands and better quality ones too, (than what you now have).

Have you rebooted the PC? Do its network drivers need updating? Are you using the proper drivers for the PC (i.e. from the manufacturer)?

 

[BaronBerserker]

Thanks @L&LD.

Whenever I switch back to my old router, this doesn't happen at all, even with the same cable, which is why I assumed it was an issue with the new router. I've also checked that both ends are securely connected multiple times. I don't have another cable to test with at the moment, either.

The PC actually has both Windows and Linux installs (on different drives). The issue happens in both OSes, even after multiple reboots, but networking drivers are correct and up to date in both.

 

[ColinTaylor]

Jan 7 19:35:02 kernel: eth1 (Ext switch port: 0) (Logical Port: 8) (phyId: 8) Link DOWN.
Jan 7 19:35:02 kernel: br0: port 4(eth1) entered disabled state
Jan 7 19:35:22 kernel: eth1 (Ext switch port: 0) (Logical Port: 8) (phyId: 8) Link Up at 100 mbps full duplex

This indicates that there is a physical problem with the connection to the PC.

The fact that it is connecting at only 100 Mbps is suspicious. Does the PC really only have a 100Mb network port?

 

[BaronBerserker]

Thanks @ColinTaylor. The port itself is a gigabit port, but the cable is definitely older - maybe it only supports 100Mbps? I guess I never noticed because our plan with our ISP has never been higher than that anyway - we're on an "up to 100Mbps" plan, and it usually tests around 90.

But speed aside, what's odd to me is that these drops never happen with the old router even with the same cable. Unless there's some kind of incompatability between the new router and the cable if the latter is old enough?

 

[ColinTaylor]

Thanks @ColinTaylor. The port itself is a gigabit port, but the cable is definitely older - maybe it only supports 100Mbps? I guess I never noticed because our plan with our ISP has never been higher than that anyway - we're on an "up to 100Mbps" plan, and it usually tests around 90.

But speed aside, what's odd to me is that these drops never happen with the old router even with the same cable. Unless there's some kind of incompatability between the new router and the cable if the latter is old enough?

Yes it's quite possible that it's a compatibility issue between the devices, particularly if you're using an old 4-wire Cat5 cable. You could try setting the network interface on the PC to 100Mb Full Duplex to see if that helps while you wait for a replacement cable.

 

[BaronBerserker]

Thanks, I'll grab a Cat6 this weekend and see if that helps.

 

[eemj]

Also note that a CAT5E or CAT6 cable can limit the speed if you have a bad connection/wire. I have seen it with new cables. 100 speed uses only four of the 8 wires where faster speeds require all 8 wires. So replace that cable.