On Sun, Jan 29, 2006 at 03:19:31PM +0100, Marco Fretz wrote:
> hello
>
> thanks again!
>
> ok, i agree my solution sounds not very simple =)
>
> i never made something wit carp. i will see the manpage and will try to
> find and read some docs.
>
> what i'm really dont understand is: how can carp to loadbalancing. if i
> get an arp answer from the first router, the next request for this ip
> will go to the same adress. so carp has do do "mac faking"? is carp
> "flooding" the subnet with random mac adresses for the same ip?
My understanding is that the following happens, if we have a CARPed
address $FW:
$CLIENT has a (default?) gateway for IP traffic set to $FW. When the
kernel receives a request to send a packet to a host on the relevant
subnet, a quick routing table lookup yields that this should be sent to
the physical (MAC) address associated with the IP address $FW. So,
$CLIENT tries to look up the MAC associated with $FW, finds nothing, and
sends an ARP query to find out who has $FW.
The hosts $FW1, $FW2, and $FW3, which together handle the CARPed address
$FW, see this query, and notice from which host it comes. Now, all three
perform some calculation, which tells them that, for example, $FW2
should handle requests from this host.
Now, $FW2 answers the ARP query, and all traffic from $CLIENT is
henceforth sent to $FW2.
Of course, this is a simplication, as the above does not fail over. In
fact, each of $FW[1-3] is a CARPed address (but without arpbalance, so
it acts as CARPed addresses typically do - communicating to find out
which is master, and the master then responds to ARP requests for the
CARPed address, as well as packets destined for that address).
Joachim
> Am Sonntag, den 29.01.2006, 13:59 +0000 schrieb tony sarendal:
> > On 29/01/06, Marco Fretz <[EMAIL PROTECTED]> wrote:
> > > is there something that i can do with carp? or how is a router cluster
> > > to realise? the problem is, i dont want a fail over, i need performance.
> >
> >
> > If you expect the traffic pattern to be from many to many directly connected
> > hosts you can let carp handle loadsharing
> >
> > carp man page:
> > net.inet.carp.arpbalance Balance local traffic using ARP. Disabled
> > by
> > I would keep it simple. Put all boxes on all lans and use carp.
> > IP routing is unidirectional, traffic from A->B doesn't have to go over the
> > same box
> > as traffic B->A. With three boxes you can get speed and a be pretty
> > resilient also.
