Subject: Re: [vserver] Problem reaching public internet from private address inside a VPS
From: Nikolay Kichukov <hijacker@oldum.net>
Date: Thu, 15 May 2008 15:54:10 +0300

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Hi Victor,

What is the status of this thread? Did manage to sort out the problem?
Is it just me who missed the rest of the thread?

Cheers,
- -Nikolay

Daniel Hokka Zakrisson wrote:
> Víctor Román Archidona wrote:
> Hi,
> 
> I'm using several VPS on the same machine with multiple public IP
> addresses. Both host and VPS machines has network conectivity and reachs
> the public Internet via eth0, which has all the public IPs.
> 
> Now I'm building "private" VPS on 172.16.1.0/24 network segment. If I
> give 172.16.1.1 to HOST and 172.16.1.10 to a private VPS, they both can
> see each other.
> 
> The problem comes when I try to reach the public internet from the
> private VPS on the private subnet. I also enabled forwarding and
> postrouting on the host:
> 
> echo 1 > /proc/sys/net/ipv4/ip_forward
> 
>> This is not needed. Guests aren't routed /through/ the host, they're
>> routed /by/ the host.
> 
> iptables -t nat -A POSTROUTING -s 172.16.1.0/24 ! -d 172.16.1.0/24 -j
> SNAT --to A.B.C.D
> 
> (being A.B.C.D the public IP address).
> 
> The VPS has the following interfaces configuration:
> ~ /etc/vservers/private/interfaces/0/dev    > lo
> ~ /etc/vservers/private/interfaces/0/prefix > 8
> ~ /etc/vservers/private/interfaces/0/ip     > 127.0.0.1
> 
>> I hope you only have this for one guest... but even then it shouldn't be
>> needed with a properly configured kernel and non-retarded applications.
> 
> ~ /etc/vservers/private/interfaces/1/dev    > eth0
> ~ /etc/vservers/private/interfaces/1/prefix > 24
> ~ /etc/vservers/private/interfaces/1/ip     > 171.16.1.10
> 
> Can anyone help me or give some hint about why I cannot reach the public
> Internet?
> 
>> What kernel? Using a private address for the first interface is a possible
>> reason if you're using an old kernel.
> 
> Regards,
>>

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