Updated: 

I found that if I mirror to a 10Mbps port, my entire WAN slows down to 10Mbps.
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Hello,

I am using an ER605 with two WAN connections. I am facing a persistent issue where:

• Download speed is limited to around 10 Mbps,

• Upload speed works normally,

• The problem only appears when using two WAN interfaces.

If I enable Failover Timing and then disable it again, the download speed returns to normal temporarily.
However, after some time, the issue comes back and the download speed cannot exceed 10 Mbps again.

I restored the backup one and it worked fine again.

Additional notes:

• Upload speed is never affected.

• Download speed is capped at ~10 Mbps until I toggle Failover Timing.

• The issue keeps repeating after some time.

• No QoS or bandwidth limit is configured.

• Load Balance enabled.

• Speed of internet 100mbps (tested using other router).

• Policy route enable for domain, ip group.

•  

It seems like the router has a problem with Dual-WAN routing, load balancing behavior, or some internal failover mechanism that causes download throughput to drop.

Could you please help identify the cause or provide a workaround to prevent download speed from being stuck at 10 Mbps?

Thank you!