We have network issue with extremely slow copy speed via GRE or IPIP IPsec tunnel. After upgrade to latest firmware version 6.30 we observed better copy speed via SCP on linux machines. But if we try to copy any files via SMB on Windows machines – speed is extremely slow.
If we turn off IPsec, we observe very good speed, as fast as ISP connection speed limit. We use on both sites CCR1036-8G-2S+
GRE MTU 1426
Don’t Fragment: no
Clamp TCP MSS is on
IPsec hash algorithm sha1, encryption algorithm aes-128
We also tried mangle rule, that changes TCP MSS in gre tunnel to 1300 – nothing changes.
It is possiple that issue is still with reordering packets.
Sites are remotes and round trip time is about 120 ms.
We also tried to change GRE MTU to 1400 without and with Mangle rule that changes MSS to 1300 - nothing happened.