Hi.
I have next scheme:
Router1 = VDS MikroTik CHR (License level P1) with single interface (ether1)
Router2 = MikroTik RB4011iGS+ (office)
On Router2 there is 2 networks on different bridges:
bridge-local = main network 192.168.253.0/24
bridge-tunnel = separated network 192.168.38.0/24
There is IPIP-tunnel between Router1 and Router2 (192.168.200.0/30) 192.168.200.1 = Router1-IPIP-tunnel address, 192.168.200.2 = Router2-IPIP-tunnel address.
Main network should use ordinary internet connection.
Separated network should use IPIP-tunnel to access the Internet
All working but:
on main network: speedtest.net = download 35 Mbit/s, upload 35 Mb/s
on separated network: speedtest.net = download 0,5 Mbit/s, upload 18 Mb/s
WHY?

On Office Router2
/routing table
add fib name=inet
add disabled=no fib name=tunnel
/ip address
add address=192.168.253.254/24 interface=bridge-local network=192.168.253.0
add address=192.168.200.2/30 interface=ipip-tunnel-test network=192.168.200.0
add address=192.168.38.1/24 interface=bridge-tunnel network=192.168.38.0
/ip firewall mangle
add action=mark-connection chain=prerouting connection-mark=no-mark in-interface=bridge-inet new-connection-mark=inet_connection passthrough=yes
add action=mark-routing chain=prerouting connection-mark=inet_connection in-interface-list=!wan new-routing-mark=inet passthrough=yes
add action=mark-routing chain=prerouting in-interface=bridge-tunnel new-routing-mark=tunnel passthrough=yes src-address=192.168.38.0/24
add action=mark-routing chain=output connection-mark=rinet_connection new-routing-mark=inet passthrough=yes
/routing rule
add action=lookup-only-in-table disabled=no dst-address=192.168.253.0/24 table=main
add action=lookup disabled=no routing-mark=tunnel table=tunnel
/ip route
add distance=251 gateway=195.91.63.65
add gateway=195.91.63.65 routing-table=inet
add disabled=no dst-address=4.2.2.1/32 gateway=195.91.63.65 routing-table=main scope=11 suppress-hw-offload=no
add check-gateway=ping disabled=no distance=10 dst-address=0.0.0.0/0 gateway=4.2.2.1 routing-table=main suppress-hw-offload=no target-scope=11
add disabled=no dst-address=0.0.0.0/0 gateway=192.168.200.1 routing-table=tunnel suppress-hw-offload=no

Ping speed in ipip-tunnel = 52Mb/s x 62 Mb/s

IPIP causing fragmentation ????
viewtopic.php?t=55124

Tried MTU on IPIP 1420, 1410... Nothing helped.
Additionally used on both routers:
/ip firewall mangle
add action=change-mss chain=forward in-interface=ipip-tunnel-test new-mss=1380 passthrough=yes protocol=tcp tcp-flags=syn

download VS upload = 1 x 15..20 times.