Re: [vserver] host-IP substituted by guest-IP ???

From: Jarry <>
Date: Sat 15 Aug 2009 - 21:20:03 BST
Message-ID: <>

Herbert Poetzl wrote:

>> It seems to me that for every connection from host, vserver-guest
>> is substituting host's IP with its own guest's IP. WHY???
> - there are no 'host' or 'guest' IPs or even interfaces
> all addresses are configured on the host, and all
> networking happens on the host, the guests just get to
> 'use' certain IPs for binding services to them
> - from the host perspective, all IPs (even those assigned
> to a guest) are local, so it is like the host is talking
> to itself.
> so, that means for your setup:
> - all host-guest or guest-guest traffic is local traffic
> which doesn't leave the host, and uses lo to transfer
> - binding to on the host will grab all IPs,
> including those assigned to guests
> - source IP selection will happen according to the
> normal Linux network stack rules

OK, but I do not understand one thing: why with guest->guest
traffic everything is OK? When guest1 talks to guest2, in logs
on guest2 there is a correct client (source) IP "guest1".
Not IP of "guest2", as it is for host->guest2 traffic...

How does host know, which of its IPs it has to select as
source_IP when one guest talks to the other? And when host
can this for guest->guest traffic, why it can not do the same
"clever" source-IP selection for host->guest traffic?

>> Can I somehow force guests to use correct host's IP?
> the guest is not involved in your source IP selection, so
> nothing in the guest (or its configuration) can affect that
> the problem is with the host finding a suitable IP for your
> host local request, and as you do not give any preference
> the host chooses one address according to its rule set,
> which might as well be the IP assigned to your guest
> you can use the 'normal' mechanism to control the source
> IP selection, or you can specify the source IP on your
> query, in any case, as long as the guest is reachable, it
> will work out fine

So can I somehow force host to use its "only real" IP
for the whole host-guests traffic? Because now looking into
guests' logs I can not say which traffic came from within
the same guest, and which came from host...


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Received on Sat Aug 15 21:21:05 2009
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