Hi,

I have a simple IPIP tunnel setup between two systems.
The tunnel is working fine.

However, iperf tests show much lower (1/5 th) throughput over the tunnel.

Throughput without tunnel: 10 Gbps
Throughput with tunnel: 2 Gpbs

MTU on physical interface eth0 is 1500
MTU on tunnel interface crtun is 1400

Any ideas why IPIP tunnel has so much
lower performance??
I have tried different MTU values as well
but no luck.


Commands Used
--------------

Server 1
sudo ip tunnel add crtun mode ipip remote 10.0.0.34
sudo ip addr add 169.254.169.250/31 dev crtun
sudo ip link set dev crtun up

Server 2
sudo ip tunnel add crtun mode ipip remote 10.0.0.35
sudo ip addr add 169.254.169.251/31 dev crtun
sudo ip link set dev crtun up

Hi,

Set the tunnel MTU to 1500-(maximum ipip header size)=1484? I'm not positive on the exact size. But it's near 1500. It might be 1492. But just experiment a bit using sensible values for tunnel MTU. The reason it has to be smaller than the MTU of the interface is to make room for the tunnel headers.