I have a RB4011 connected to a CRS305 with a router-on-a-stick topology, with sfp-sfpplus1 on RB -> sfp-sfpplus1 on CRS, both with 10G ethernet SFP+ modules. The sfp-sfpplus4 port on the CRS goes to the ISP's fiber internet CPE which provides a public IP address to the RB4011 on the VLAN 10 network that I set up between the RB and CRS. The problem is, I can't get past around 60 Mbps on upload, while I can get an easy 900 on download. I've checked everything including fasttrack, queues, CPU usage, accidental VPN usage, but no luck. The weird part is that when I connect straight to the CPE, I get an easy 900 Mbps upload speed, the same as download because I have a symmetric gigabit connection. This also never happened before the router-on-a-stick setup so the problem has to be there. I get hw-offloading on ALL the ports of the CRS305, even with VLANs and bridge VLAN filtering, so it's not a switch chip issue. When doing a speedtest, the RB4011's CPU reliably goes to around 90% on one core when doing download but 10% on upload, so it's definitely powerful enough. Also, bridge VLAN filtering is enabled on the RB4011 but it might not need to be. What is there left to check? I haven't touched MTU or flow-control or anything like that.
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