[vbox-dev] Virtualbox NAT and TTL mangling ISPs

Alexey Eremenko al4321 at gmail.com
Thu Dec 3 14:41:39 GMT 2009

On Thu, Dec 3, 2009 at 4:31 PM, Lucian Adrian Grijincu
<lucian.grijincu at rosedu.org> wrote:
> Hi,
> My ISP decided to reduce the number of computers that would connect to
> their network on a single connection by mangling with the TTL of IP
> packets.
> For now it sets the TTL of all incoming packets to 1.
> When a host receives a packet destined for a Virtualbox vm, it will first
> decrement the TTL before deciding where to forward it.
> Because TTL is now 1 the host will drop the packet.
> This fixes it for me:
>  iptables -t mangle -A POSTROUTING -j TTL --ttl-set 64
> but it took me a while to come up with the fix.
> It would be nice if the Virtualbox GUI or the manual would
> list this work-around (or a better one if someone finds something
> better) and, ideally, the GUI could provide a way to enable non
> experienced users to run this command automagically.

Since your situation is a rare one, it should not belong to VBox
official docs, but you can write an article, and we may consider
putting it here:

-Alexey Eromenko "Technologov"

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