GRE tunnel
 

Hi everybody
I have setup tunnel between tow Linux servers, But its performace is very low,when I sniff transaction by Wireshark, very lines is labeled with "TCP Dup ACK" or "TCP Retransmission" or "TCP Previous segment lost".
I know about this issue.
Thanks for any help or guidance .

Lower the MTU on the tunnel interfaces to 1450 or so to account for GRE overhead. Your packets may be getting fragmented somewhere along the way, which can cause issues.