EoIP on CCR without fastpath = HORRIBLE performance

Am I missing something?

The background / setup.

Router A CCR1009-8G-1S-1S+
Bridge-LAN [ether-2, eoip-tunnel]
ether-8 Static IP on /30 (directly connected to Router B)

Router B CCR1009-8G-1S-1S+
Bridge-LAN [ether-2, eoip-tunnel]
ether-8 Static IP on /30 (directly connected to Router A)

EoIP Tunnel between Router A and Router B.
No Encryption
Yes Fastpath
Yes Clamp TCP MSS


Laptop A connected to Router A's ether-2 at 1000Mbit/FD

Laptop B connected to Router B's ether-2 at 1000Mbit/FD


Copying large files from Laptop A to Laptop B runs at 960Mbit.... Great.
(Windows SMB file copy)

Now, disable fastpath
The same filecopy runs at 15Mbit.

Now add in a passphrase to enable IPSec (which requires disabling fastpath).
With default profile set to AES-128-CBC and No Auth we're now at 7.5Mbit

This is abysmal. What's going on? ...and more importantly, can anything be done to fix it?

Sorry, forgot to include RouterOS 6.34.6