﻿id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
9440	NAT networking rewrites the DF (dont fragment) flag	Oleg		"I found that NAT network removes, improperly, he IP packet DF flag (dont fragment) when the packet is crossing the boundary of the NAT networking. The bridged network works fine.

Environment:

    VirtualBox 4.1.0 
    Host OS Windows 7
    Guest OS Linux 2.6.38

Problem: 

    When we send a UDP packet (I tested only UDP) with DF flag set (0x02) in the IP header, to the ""outside world"", it appears on the wire outside of the NAT network as having the IP flags as 0 - the DF flag disappears.

    The same is true on the receiving side: when the packet on the wire has 0x02 flag set in the IP header, it is getting delivered to the NAT network with flags 0.

    When I am changing the networking settings to ""bridged"", everything works normally - the DF flag is preserved both ways. So, this is NAT-only problem, but rather annoying for some advanced applications which have to perform PMTU discovery, for example.
"	defect	closed	network/NAT	VirtualBox 4.1.0	fixed	DF, fragmentation, dont fragment		Linux	Windows
