Solution Steps

1. Find optimal MTU: Ping test with different packet sizes.
2. Command: ping -f -l 1472 8.8.8.8 (Windows)
3. If packets fragment, reduce size until no fragmentation.
4. Set MTU in router settings: Advanced → WAN → MTU.
5. Or set on Windows: netsh interface ipv4 set subinterface "Wi-Fi" mtu=1500 store=persistent
6. Common MTU values: 1500 (Ethernet), 1492 (PPPoE), 1454 (PPPoA).
7. Restart router and device after changing MTU.