Connection instability on ASUS RT-AC56U & VLAN disconnect

[#1]

I've been using the AC56U for years as it practically does any connection type imaginable. The speed is not usually an issue but stability has been lacking with frequent disconnects of several minutes at a time, sometimes requiring manual resetting.

I understand that some ASUS machines are known to be less stable on UK FTTC lines but this seems to be beyond that. Most oddly, the connection to the fibre modem is lost when I turn VLAN on (802.1Q enabled and set to 101Q/0P). As soon as I disable VLAN, I'm back online but with the described instability ...

Any ideas?

[#2]

Most oddly, the connection to the fibre modem is lost when I turn VLAN on (802.1Q enabled and set to 101Q/0P). As soon as I disable VLAN, I'm back online

not odd at all! The modem does the vlan tagging, so the router shouldn't do any tagging at all

[#3]

I see, that clears it up. Plusnet guidance consistently advises to have VLAN on even with fibre connections.

So only the connection instability remains to be investigated!

[#4]

Is the modem losing sync ?

[#5]

Looks like it, the local network is always intact. It mostly self-corrects after a few minutes but today I had to power the lot off and switch back on in sequence, that only happens every so often.

[#6]

Does the ASUS have any readable error logs?

[#7]

If the modem is losing sync, then either logs or linevstats from the modem are going to be the  most useful

[#8]

Sorry, @MisterW didn't think of that - do modems (whichever the OP is using) have these facilities?

[#9]

@jab1 they do, but getting access to them can be difficult

[#10]

Is there not an expectation to be able to view the PPPoE connection behaviour on the ASUS router? I could on a TP-Link router.

Agree to view the DSL behaviour you need access to the modem logs unless it is connected to a ONT. (No DSL)

@chaptainsky which modem is being use?

[#11]

I suspect the issue lies with the PPPoE connection. The modem is an openreach-supplied box, I'll get the serial number later. It's wall-mounted and doesn't give away much ...

I'll see about pulling the router logs though.

[#12]

If the modem is losing sync , then you wont get much information from the router logs, other than the PPPoE connection has been dropped!

[#13]

Not disagreeing but limited information is better than no information, the frequency of any PPPoE connection drops can be determined confirming the effort to extract the DSL connections a worthwhile task.

The described issue could be DSL drops.