Subject: Re: [vserver] Loopback issues
From: Jeff Williams <jeffw@globaldial.com>
Date: Mon, 27 Aug 2007 15:13:29 +0800

Daniel Hokka Zakrisson wrote:
> Jeff Williams wrote:
>   
>> Daniel Hokka Zakrisson wrote:
>>     
>>> Jeff Williams wrote:
>>>
>>>       
>>>> <snip>
>>>> On a regular server, assigning 4.3.2.1 as an alias of the loopback
>>>> interface allows the server to accept packets for 4.3.2.1 while not
>>>> announcing that ip to the rest of the network. However, on the vserver
>>>> host, because the host sees the 4.3.2.1 address, all traffic from other
>>>> vservers (e.g. the web server) for the ip gets  routed directly to the
>>>> vserver rather than to the lb.
>>>>
>>>> I can't see any way around this. The lb sends a packet with mac address
>>>> of the vserver host and the address 4.3.2.1. Therefore the host needs
>>>> to
>>>> be aware of the IP. However, once it is aware of the IP, it routes the
>>>> traffic from all of the other vservers. Any ideas? I can only think of
>>>> playing with iptables rules, but that doesn't seem like fun.
>>>>
>>>>         
>>> Seems to me like iptables -t nat -A PREROUTING -i ethX -d 4.3.2.1 -j
>>> DNAT
>>> --to 1.2.3.4 should do the trick...
>>>
>>>
>>>       
>> Thanks Daniel, but I don't have problems with traffic from the lb
>> getting to the mail vserver. My problem is that mail traffic from the
>> other vservers goes directly to the mail vserver rather than the lb.
>>     
>
> If you don't add the IP address to the host at all and just use that
> iptables rule, would there be a problem? IMHO it should solve all of your
> problems...
>
>   
I didn't even think of it that way. I will set up a test virtual IP to
try it on.

Thanks,
Jeff