I am running OpenWrt 19.07.3 as a guest operating system in a VMware ESXi host. It is functioning as both a router and a switch. I am trying to enable Jumbo Frames to possibly improve performance when talking to another VM that is acting as a NAS.
My setup is
I have an Intel I350 network adapter that is directly pass-through to the OpenWrt VM. The adapter should support Jumbo Frames up to 9.5K according to their product brief. My laptop is connected to this adapter directly, and it also supports Jumbo Frames. (
r8169 0000:03:00.0 eth0: jumbo features [frames: 9194 bytes, tx checksumming: ko])
OpenWrt VM is also connected to an ESXi virtual switch using the VMXNET 3 adapter. The virtual switch is set to have an MTU of 9000 and my NAS VM is also connected to this virtual switch.
In the OpenWrt VM, all LAN interfaces are connected to a bridged interface (br-lan), and they are set to have MTU of 9000. (
ip ashows all interfaces have MTU of 9000)
The current situation is I can ping the OpenWrt VM from my laptop or the NAS VM using
ping -M do -s 8972 (openwrt ip) without any issue, but if I try to ping from my laptop to the NAS VM using the same command I got
ping: local error: message too long, mtu=1500.
How can I fix this?