Slow and Intermittent traffic on IPSec site to site

[posemman]

All,

Did you experience intermittent connection when enabling IPSec FG-FG as a backup route when MPLS is also up?

Remote Site:

MPLS connection is the primary using static route w/ 10 AD and priority of 0

While the IPSec is the secondary connection w/ 10 AD and priority of 100

when I enable the IPSec connection we always encountered slow response/intermittent traffic going to HQ.

Seem the traffic flow is confuse on where to send(should be on MPLS or IPSEC).

Supposedly the traffic should always go thru MPLS, since this circuit is not down. 

Hope to find solution on this. Thank you

[patelr]

Hello @posemman ,

Have you tried adjusting MTU and TCP MSS setting, NAT traversal ? By chance, do you have any available logs to review?

Thanks,

Ronak Patel

[arahman]

Hi @posemman , also please try disabling the UTMs if there is any and see if there is any  UTM causing the slow speed and also perform the iperf test as shown below to see if it ipsec tunnel that is slow 

https://community.fortinet.com/t5/FortiGate/Technical-Tip-How-to-troubleshoot-speed-issue-through-IP...