LAN Switch enable bonding and disable STP kills LAN

[stephen_d_hill]

I have enabled LAN->Switch Control ->LAN bonding on my RT-AX86U, and connected both cables to an my LANs Eth switch which has enabled Active LACP on those ports. This seems to work okay (checked logs of switch and router). But, if I disable STP (LAN->Switch Control ->Spanning-Tree Protocol) I lose the LAN ... the question is why?

 

[ColinTaylor]

Make sure your switch ports are configured for 802.3ad and not one of the other aggregation modes. It sounds like link aggregation on the switch isn't working at all and therefore STP is preventing a loop condition.

 

[stephen_d_hill]

I am using an HP1810-8G Eth switch ... it only supports LACP (802.3ad). I have set the trunk on the switch to 'LACP Active'.

 

[stephen_d_hill]

The trunk connected to the RT-AX86U is TRK2 (WiFi) and seems to be working, given there are packets seen on both interfaces/ports from the Eth switch GUI:

Trunk	Name	Type	Admin Status	Link Status	Static Mode	Trunk Members	Active Ports
TRK1	Server	Dynamic	Enable	Up	Disable	7,8	7,8
TRK2	WiFi	Dynamic	Enable	Up	Disable	1,2	1,2

Port Statistics:

Interface	Received Packets w/o Error	Received Packets with Error	Broadcast Received Packets	Transmitted Packets w/o Errors	Transmitted Packets with Errors	Collisions	Transmitted Pause Frames	Received Pause Frames
1	117685472	0	2026502	86128466	0	0	0	0
2	275559084	20	814382	307215035	0	0	0	0

Trunk Statistics:

Trunk	Received Packets w/o Error	Received Packets with Error	Broadcast Received Packets	Transmitted Packets w/o Errors	Transmitted Packets with Errors	Collisions
TRK1	597519016	83	4737514	777767783	0	0
TRK2	393244556	20	2840884	393343501	0	0

 

[stephen_d_hill]

 

[ColinTaylor]

Is your Asus in "router mode"?

 

[stephen_d_hill]

Is your Asus in "router mode"?

Operation Mode:Wireless router Firmware Version:386.7_2

 

[ColinTaylor]

I can't think why turning STP off would cause a problem. Presumably the router reboots itself after changing STP modes?

If you SSH into the router and turn STP off from the command line does the same problem occur:

# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.f02f749237d8       yes             eth1
                                                        eth2
                                                        eth3
                                                        eth4
                                                        eth5
                                                        eth6
                                                        eth7
                                                        wl0.2
# brctl stp br0 off
# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.f02f749237d8       no              eth1
                                                        eth2
                                                        eth3
                                                        eth4
                                                        eth5
                                                        eth6
                                                        eth7
                                                        wl0.2

Obviously your interface names will be different than mine.

 

[stephen_d_hill]

I can't think why turning STP off would cause a problem. Presumably the router reboots itself after changing STP modes?

The router does reboot, yes, after changing STP mode.

 

[stephen_d_hill]

If you SSH into the router and turn STP off from the command line does the same problem occur:

# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.f02f749237d8       yes             eth1
                                                        eth2
                                                        eth3
                                                        eth4
                                                        eth5
                                                        eth6
                                                        eth7
                                                        wl0.2
# brctl stp br0 off
# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.f02f749237d8       no              eth1
                                                        eth2
                                                        eth3
                                                        eth4
                                                        eth5
                                                        eth6
                                                        eth7
                                                        wl0.2

Obviously your interface names will be different than mine.

Here's mine:

# brctl show br0
bridge name    bridge id        STP enabled    interfaces
br0        8000.fc34978b2a58    yes        bond0
                            eth1
                            eth2
                            eth5
                            eth6
                            eth7
# brctl stp br0 off
# brctl show br0
bridge name    bridge id        STP enabled    interfaces
br0        8000.fc34978b2a58    no        bond0
                            eth1
                            eth2
                            eth5
                            eth6
                            eth7

Interestingly after manually disabling STP ... is still working ok.

 

[stephen_d_hill]

Here's mine:

# brctl show br0
bridge name    bridge id        STP enabled    interfaces
br0        8000.fc34978b2a58    yes        bond0
                            eth1
                            eth2
                            eth5
                            eth6
                            eth7
# brctl stp br0 off
# brctl show br0
bridge name    bridge id        STP enabled    interfaces
br0        8000.fc34978b2a58    no        bond0
                            eth1
                            eth2
                            eth5
                            eth6
                            eth7

Interestingly after manually disabling STP ... is still working ok.

Does this suggest that there's a boot problem on the RT-AX86U?
That is, the Eth ports are being enabled before the bridge is created and hence creating a network loop on the Eth fabric?

 

[ColinTaylor]

Does this suggest that there's a boot problem on the RT-AX86U?

It does sound like a bug.

That is, the Eth ports are being enabled before the bridge is created and hence creating a network loop on the Eth fabric?

You only said the problem was "lose the LAN" which isn't particularly detailed. You could look through the code here (as you're using Merlin's firmware).

On the other hand you could just leave STP enabled as I can't see it doing any harm.

 

[stephen_d_hill]

You only said the problem was "lose the LAN" which isn't particularly detailed.

Well, is rather difficult to see what's going on as everything I have is connected to the Eth switch and the RT-AX86U ... I suppose I could enable loopback protection or STP on the HP1810-8G (currently disabled), as it will log the problem and disable the port(s) to keep at least the Eth part of the network going.

 

[thecheapseats]

@colin and @stephen_d_hill - the default for STP is 'on' - but there is something odd with STP in the off position in some configurations...

in the last few years, I had two configs I'd implemented,that didn't quite behave when turning STP off (assuming the 'help' it was giving me might have been the problem)...

particularly with a managed cisco-switch, I'd configured link-ag on the switch, a nas and the router - flattened/disabled the vlans on the switch and was flipping STP on/off to troubleshoot the problem (an AX88 at the time)...

turned off STP on the asus router to troubleshoot the issue and it bit me on the backside with same symptoms I'm reading here - a reboot and the link-ag wasn't passing packets...

I left the switch config'd and threw an EOL cicso router from my junk pile at the problem and everything functioned as expected... my guess it was a problem with the asus - but at the time I couldn't be bothered messing with it due to time constraints...

I often wondered if the managed switch's STP was set to 'on' which may have created conflicts (just guessing)... this was the second time I encountered an oddity with flipping asus STP on/off...