We have a cluster of machines providing various services using
LVS direct routing. For those not familiar with this, a typical
server has three IP addresses:
 (1) A normal public IP address, unique to that machine;
 (2) A public IP address, shared with several other machines;
 (3) A private IP address.
Normally we have address (1) accepting ssh connections for maintenance
only. Services such as http or telnet or ftp or rsync try to connect
to address (2), and are directed by the LVS director to the appropriate
server, using (for various reasons) (3) as a routing address. To do
this, we use a Linux kernel with the so-called 'hidden arp' patch
applied. On a normal machine I do something like this:
 insmod dummy
 echo 1 > /proc/sys/net/ipv4/conf/all/hidden
 ifconfig dummy0 127.0.0.2 -arp
 echo 1 > /proc/sys/net/ipv4/conf/dummy0/hidden
 ifconfig dummy0 <address (2)> netmask 255.255.255.255 -arp up
 /sbin/ifconfig dummy0:0 <address (3)> up
in order to activate addresses (2) and (3).
Now, I would like to have virtual machines running under Xen which
can do the same thing. I was able to add the 'hidden arp' patch
to the Linux kernel for domU without any problems, but it isn't
any use without the dummy kernel networking module, which won't
compile. Of course, I can add addresses to eth0:0, but doesn't this
interfere with the normal address (1) if I have hidden arp enabled
for eth0?
Is anyone else running servers under Xen using LVS direct routing?
 -- Owen
 Dr A V Le Blanc
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