Mikrotik CAKE on GPON + PPPoE

Most CAKE guides assume a plain Ethernet uplink, but GPON works just as transparently — so you can treat it like a normal Linux CAKE setup.

The Issue

        ┌───────────────────┐
        │  Customer Router  │
        │ (PPPoE Client)    │
        └───────┬───────────┘
                │  PPPoE over Ethernet / GPON / XGSPON
                ▼
        ┌───────────────────┐
        │   ISP Access NW   │
        │   (OLT / Switch)  │
        └───────┬───────────┘
                │
                ▼
        ┌───────────────────┐
        │      ISP BNG      │
        │   (PPPoE Server)  │
        └───────────────────┘


Normal Operation:
────────────────────────────────────────────────────────────
[Client] --- PPP Echo Request ---> [BNG]
[Client] <--- PPP Echo Reply ----- [BNG]
(Session stays alive)


When Problem Happens:
────────────────────────────────────────────────────────────
[Client] --- PPP Echo Request --->  X (Lost in network)
[Client] ............................ (No reply)

BNG times out, sends PPP Terminate to client:
   [BNG] --- PPP Terminate Req ---> X (Lost in network)

Client never gets terminate request,
TX queue starts to drop, session "hangs"
until client manually or automatically reconnects.

Why This Matters

My ISP enforces a strict PPPoE session policy. If PPP Echo packets get lost somewhere, their PPPoE AC will disconnect the session. The client won’t immediately receive a Terminate Request, so the session hangs for a few seconds and TX queues start to drop until the PPPoE client reconnects.

This can momentarily halt your internet, which is unacceptable for latency-sensitive tasks.

The Fix: Apply CAKE on the Parent Interface

Instead of relying on the default only-hardware-queue (which blindly sends packets without knowing which ones are critical), put CAKE directly on the parent interface.

• This ensures high-priority packets like PPP Echo, TCP ACKs, and pings don’t get dropped.
• It’s more effective than using an egress limit on a switch port — but you can use both for granular TX control.

Tip:
If your router supports egress shaping at the switch level, set the GPON upload egress limit to 1244 Mbit/s.

Step 1 — Fix Mikrotik’s Hardware Queue

MikroTik’s default hardware queue isn’t great for fairness or packet prioritization.
We’ll replace it with mq_pfifo to help reduce LAN TX drops:

/queue type add name=multi-queue-ethernet kind=mq-pfifo mq-pfifo-limit=1000
/queue interface set [ find default-queue=only-hardware-queue ] queue=multi-queue-ethernet

Step 2 — Add CAKE for GPON ONU

This CAKE config is tuned for a 1.2 Gbps GPON uplink:

/queue type add name=cake-gpon-onu kind=cake \
cake-bandwidth=1200M cake-overhead=50 cake-mpu=84 \
cake-rtt=300 cake-rtt-scheme=oceanic \
cake-diffserv=diffserv8 cake-flowmode=triple-isolate \
cake-ack-filter=aggressive cake-wash=yes cake-memlimit=33554432

If you have a GPON OLT stick running in 2.5 G mode:

/queue type add name=cake-gpon-olt kind=cake \
cake-bandwidth=2400M cake-overhead=50 cake-mpu=84 \
cake-rtt=100 cake-rtt-scheme=internet \
cake-diffserv=diffserv8 cake-flowmode=triple-isolate \
cake-ack-filter=aggressive cake-wash=yes cake-memlimit=33554432

Parameter Notes

• Overhead (50 bytes) → Includes IFG, preamble, CRC, VLAN, and PPPoE.
• MPU (84 bytes) → Keeps small packets (PPPoE discovery, ping, TCP ACK) from being dropped — crucial for PPP Echo stability.
• RTT (300 ms) → Matches long-haul latency (e.g., Europe ↔ Singapore).
• diffserv8 → Gives detailed classification — Network Control (BGP, routing updates, PPP Echo) gets top priority.

diffserv8 Classification

Priority	DSCP	Value	Typical Use
2	CS6	48	Network control (BGP, OSPF, PPP Echo, ICMP)
3	EF	46	Real-time voice (VoIP, SIP RTP)
4	AF41	34	Video conferencing / interactive video
5	AF31	26	Streaming video / high-priority data
6	AF21	18	Bulk interactive (gaming, SSH)
7	AF11	10	Standard data / normal web traffic
8	BE	0	Best effort / VPN / Wireguard / background sync / torrents

The Priority 1 mainly internal ISP/IX, and ISP ignore such marking

Step 3 — Apply CAKE to the WAN Interface

Finally, put CAKE on your GPON WAN port:

/queue interface set sfp-sfpplus1 queue=cake-gpon-onu

It should look like this

Result

Great for routers without a switch chip — keeps 2 Gbps GPON + PPPoE rock-solid.

Smooth, stable PPPoE sessions.

No random session drops from missed PPP Echo packets.