Cannot work with MTU sizes larger than 2 KB => Fixed in SVN

[JFMG]

I have the following setup:

• Host OS: Windows 7.
• Guest OS: CentOS Linux 7.
• Bridged adapter:
  • Host NIC: Intel(R) 82579LM Gigabit Network Connection. This NIC has jumbo packets (9014 bytes) enabled in Windows.
  • Adapter type: any of the three Intel adapter types available.

I set the MTU size to 5000 bytes (using the corresponding "/etc/sysconfig/network-scripts/ifcfg-enp0sx" file) and I succeed ("ip a" command shows it).

Then I try to ping from the guest NIC to the host NIC or vice versa, I can do it with the default ping packet size or even with 2000 byte packet size (which I couldn't before setting the MTU size to 5000 bytes), but not with larger packet sizes. Of course, pinging with larger than 2 KB packets works when I do it between host LAN NICs.

I've tried with a Fedora image and I get the same results.

[JFMG]

First part of the screenshot in the guest

[JFMG]

Second part of the screenshot in the guest

[JFMG]

Screenshot in the host

[JFMG]

Three more things:

• I've tried using the latest testbuild with the same results.
• I've search the forums with no information on this.
• I created a forum post but got no relevant suggestions.

[Aleksey Ilyushin]

Please try the latest Windows test build. It should solve the issue.

[JFMG]

Hi aleksey: yes, it does solve the issue. Now it works even with packets bigger than the MTU I define (I don't know why).

Thanks for your prompt support.

[Aleksey Ilyushin]

Replying to JFMG:

Hi aleksey: yes, it does solve the issue. Now it works even with packets bigger than the MTU I define (I don't know why).

Did you do "ping -M do" to disable fragmentation?

Thanks for your prompt support.

You are welcome.

[Frank Mehnert]

Fix is part of VBox 5.0.16.