GRE tunnel performance SLA

[BensonLEI]

Hi, guys,

I am using Fortigate 400E, 600E with FortiOS v6.4.2 and V6.4.4. For some reasons, my company perfers GRE tunnel.

It is found that the poor performance SLA of the GRE tunnel between two fortigates  ( often some percentage of packet loss often found, while the internet lines are running well - no packet loss ), any advice, thx a lot ?

Any article/doc to fine tune the GRE tunnel parameters/attributes ?

[pavankr5]

Hello @BensonLEI 

Once check MTU size is properly configured on both ends of the GRE tunnel. Misconfigured MTU settings can lead to packet loss and performance issues. adjusting the TCP MSS value to prevent fragmentation issues
Understanding PMTU on GRE tunnel and using fragmentation to recover the tunnel traffic
let us know if this helps

Thanks
Pavan