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On Sat, Nov 04, 2000 at 12:02:29AM +0000, Julian Anastasov wrote:
> On Fri, 3 Nov 2000, Ard van Breemen wrote:
> > Some investigation revealed however that in the normal setting up,
> > the real-servers can use the VIP on the ip level when connecting to
> > outside. Using the ip tool instead of ifconfig and route reveals why:
> > On every route we can define the preferred IP-source ourselves. In
> > this case somehow (with network IP reconfigurations, putting real-ip
> > (i.e. not the 192.168 range) addresses on the "primary" interface) the
> > VIP became the preferred source address. But reading the IP manual
> > revealed that setting up preferred source addresses is really easy:
> > ip route change ..... src realserver-ip. In the case we are setting
> > up it is not necessary because on the realserver, the kernel sees
> > that both the DIP and the VIP are secondary addresses of the primary
> > real-server ip and hence will not be used as source-ip. Only the
> Oh, yes, this is a known issue, handled from hidden=1:
>
> Documentation/proc.txt:
Hmmm, how often do I need to reread all of the linux/Documentation ?...
(Allright, this options has been there for a long time... mumble mumble)
> hidden
> Hide addresses attached to this device from another devices.
> Such addresses will never be selected by source address autoselection
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> mechanism, host does not answer broadcast ARP requests for them,
> ^^^^^^^^^
Allright, but in our case it HAS to answer to broadcast ARP's. Our
monitor depends on it...
> does not announce it as source address of ARP requests, but they
> are still reachable via IP. This flag is activated only if it is
> enabled both in specific device section and in "all" section.
Hmmm, then it can only be reached by means of gatewaying....
> > router will think that the VIP is not directly acccesible, but in fact,
> > every local system can reach it directly (in the same subnet).
> > Arping the VIP is not a problem now, but a mere tool to see which hosts
> > are up and useable for loadbalancing for that particular VIP :).
So, hidden does not completely suit our needs, we need the arp :).
But by using ip (I mean the tool), we can prevent using the VIP as
source...
Thanx for your insight,
--
Ard van Breemen, T(elegraaf)E(lektronische)M(edia)
http://leerquoten.monster.org/ http://www.faqs.org/rfcs/rfc1855.html
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