VXLAN, Virtual Switch and MTU

[irisit]

Hi, I have successfully connected a main office to a branch office using a VXLAN over an IPSec tunnel. The tunnel is connected at each end to a soft switch, which also contains a physical LAN port. Everything appears to work correctly from the branch office; however, the main office is having issues accessing certain websites. These websites can be accessed from the branch office without issue. If the tunnel is removed from the soft switch in the main office there is no issue accessing the websites from the main office.

I found the following article which describes the situation: VXLAN interface impact on software switch... - Fortinet Community. 

Based on the article I set honor-df to disable which appears to have corrected the problem but am not sure if this will have other ramifications across the network. Is this the best way to correct this problem, of is there another solution?

Thanks in advance for any help.

Regards Robert Andrews

[Shashwati · Accepted solution]

set honor-df disable

FortiGate to ignore the 'do not defragment' portion of a packet.  if user is trying to use an MTU bigger than Firewall interface MTU without fragmentation , the packets are still allowed

https://community.fortinet.com/t5/FortiGate/Technical-Tip-Explaining-the-honor-df-global-setting/ta-...

[irisit]

Thanks for your help.

I came across the article and implemented that solution but was just wondering if there were side effects of this setting.

Cheers Robert