I’ve been troubleshooting a persistent PPPoE instability issue, and have now isolated a consistent pattern with the Archer BE3600 (BE230 EU/2.0) running firmware 1.3.1 Build 20260319 rel.25411(4555).

Has anyone else seen:

• PPPoE instability on BE3600 / BE230
• PAP AuthNak loops when IPv6 is enabled
• IPv6CP still appearing even when IPv6 is disabled in IPv6 Internet settings

I would appreciate confirmation whether this is:

• a known firmware issue
• ISP compatibility issue
• or misconfiguration on my side

Problem summary

When IPv6 is enabled, the router repeatedly fails to maintain a stable PPPoE session.

The failure occurs after normal PPPoE discovery and LCP negotiation, at or around authentication / session establishment.

Key error observed:

• PAP AuthNak Request Denied
• Failed to authenticate ourselves to peer
• Repeated PPP reconnect loops (PADT → PADI → PADO → PADR → PADS cycles)

Problem Details

With IPv6 enabled:

• PPPoE discovery succeeds (PADI/PADO/PADR/PADS)
• LCP negotiation succeeds
• PAP authentication intermittently fails
• WAN session drops and reconnects in a loop - connections lasting a maximum of around 20 seconds
• Logs show repeated authentication rejection and session reset cycles

With IPv6 disabled:

After disabling IPv6 in the router UI:

• PPPoE connects immediately and consistently
• PAP AuthAck succeeds reliably
• IPCP completes normally
• WAN connection becomes stable - 55 minutes so far and counting
• No further disconnect loops observed

Even with IPv6 disabled in the UI, logs still show:

• ppp receive IPV6CP ACK

This suggests IPv6CP negotiation may still be occurring at the PPP stack level even when IPv6 is “off” in IPv6 Internet settings.

Hypothesis

This looks like a possible firmware-level issue, involving PPPoE authentication timing instability when IPv6CP negotiation is active

Specifically:

• IPv6CP negotiation overlaps with PAP authentication phase
• Firmware may mishandle retry/backoff timing
• Result is intermittent AuthNak responses and session teardown

Environment notes

• Router: Archer BE3600 (BE230 EU/2.0)
• Firmware: 1.3.1 Build 20260319
• ISP: PPPoE (credentials verified working on other routers)
• MTU: 1492
• No VLAN changes
• Issue reproducible consistently

Workaround (current)

Disabling IPv6 fully stabilises the connection.

Any solutions for IPv6 would be appreciated