Trying to get Jumbo Frames working

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. (dmesg reports 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 a shows 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?

@EffesIUC6WIxFY3F, welcome to the community!

  • Does this provide a clue?
  • Have you looked at tcpdump or Wireshark?

I'll be looking at your laptop configs.

I don't see how is this an OpenWrt issue.
Is the laptop and the NAS VM in the same broadcast domain?

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Just found out I forgot to disconnect my laptop from wifi, after doing that jumbo frames seems to be working.

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