Re: DR

Rick Willmore <[email protected]> wrote:
> I was curious if someone could help clear up a question for me.  I would
> like to know how a packet is sent from a load balancer to the individual
> nodes that have a dummy interface up and running and then the packet is
> sent out a totally new route back to the user ?  

In a nusthell, the Linux Director just forwards the packet
to the real-server, in much the same way that routers forward 
packets. 

You can think of it as if the original packet has the desination
MAC address changed from that of the linux-director to that
of the real-server, and is then sent out to the appropriate 
ethernet device.


> Do I have a different
> gateway on the dummy interface ?  

Thats probably not a good idea. Just make sure the real-server's
gateway is _not_ the linux director.

> Is the packet re-stamped with the
> dummy interface IP which reflects the VIP that the packet was sent to
> initially by the user?

No. 

> I don't want the packet to go back out the load
> balancer that it came in, I want it to go directly to the end user and
> am unclear on how the mechanism works. 

As far as the real-server is concerned, it recieves connections
from the end-user. As far as the real-server is concerned,
in terms of packets for a connection, the linux-director might as
well not exist at all. So imagine your routing setup for return
packets as iff the linux-director was not there. If the real-server
can route packets back to the end-user, and the first hop back
to the end-user is _not_ the linux-director, you are in good shape.

If the end-user is on the same LAN as the real-server (and
linux-director), then the real-server can just send the return
packets directly to the end-user over the LAN. And if the
end-user is on a different network, then the real-server
just sends the packets to the gateway (not the linux-director), 
and it forwards them from there.

> Hopefully I am clear in my
> question as I was unable to find a good description in the
> documentation.

-- 
Horms


-- 
Ultra Monkey - http://www.ultramonkey.org/
To UNSUBSCRIBE, email to [email protected], with a body:
unsubscribe ultramonkey-users [email protected]
where "[email protected]" is YOUR email address.