﻿id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
11871	NAT drops packets bigger than 388 byte towards guest	Lukas Tribus		"NAT mode does not work for me, because all packets bigger than 388 byte (IP packet length; 368 byte IP payload or 360 byte ICMP payload) are dropped.

The test is as simple as:
{{{
ping google.com -s 360
ping google.com -s 361
}}}

or on Windows guests:
{{{
ping google.com -l 360
ping google.com -l 361
}}}

The former (360 byte ICMP payload) works, while the latter (361 byte ICMP payload) doesn't.


I can reliably reproduce this with both Linux and Windows guests (32 and 64bit), on different hardware. The host always runs Windows Vista or Windows 7, both 64 bit. I did not test different host OS'.

This is with VirtualBox-4.2.12, but I can also reproduce this with the old VirtualBox-3.2.16.

The traffic of the testcase has been captured:[[BR]]
 nictrace.cap::
  via the nictrace feature; it is clear that the answer packets do not reach the guests
 host-dump.cap::
  via Wireshark on the host; all answer packets are seen (frame >= 25)


I have no clue why others don't see this behavior; on all my VirtualBox installations I see exactly this issue, and they are different installations on different hardware with different software.

Bridging mode works perfectly fine on those installations.
"	defect	closed	network/NAT	VirtualBox 4.2.12	fixed	mtu		all	all
