[Pacemaker] RES: "Using ldirectord" page question

[Carlos Xavier]

Hi.

The virtual IP on the loopback are needed for the real servers, so as they
can answer the packets sent to them.
You also need to edit the file /etc/sysctl.conf to disable the reply to arp
requests of the virtual addresses configured on the loopback.
This is what I had to add to my web servers sysctl.conf, adjust it to your
configuration:
########
# Enable configuration of arp_ignore option
net.ipv4.conf.all.arp_ignore = 1

# When an arp request is received on eth0, only respond if that address is
# configured on eth0. In particular, do not respond if the address is
# configured on lo
net.ipv4.conf.eth0.arp_ignore = 1

# Ditto for eth1, add for all ARPing interfaces
net.ipv4.conf.bond0.arp_ignore = 1
net.ipv4.conf.vlan0.arp_ignore = 1


# Enable configuration of arp_announce option
net.ipv4.conf.all.arp_announce = 2

# When making an ARP request sent through eth0 Always use an address that
# is configured on eth0 as the source address of the ARP request.  If this
# is not set, and packets are being sent out eth0 for an address that is on
# lo, and an arp request is required, then the address on lo will be used.
# As the source IP address of arp requests is entered into the ARP cache on
# the destination, it has the effect of announcing this address.  This is
# not desirable in this case as adresses on lo on the real-servers should
# be announced only by the linux-director.
net.ipv4.conf.eth0.arp_announce = 2

# Ditto for eth1, add for all ARPing interfaces
net.ipv4.conf.bond0.arp_announce = 2
net.ipv4.conf.vlan0.arp_announce = 2
########

I´m configuring some servers to work with ldiretord, but my approach as a
little bit different, I already have a cluster working for mysql and they
will be the ldirector manager and I configured anther cluster just to manage
http/https

Regards,
Carlos


-----Mensagem original-----
De: Dennis Jacobfeuerborn [mailto:dennisml at conversis.de] 
Enviada em: segunda-feira, 3 de setembro de 2012 23:28
Para: pacemaker at oss.clusterlabs.org
Assunto: [Pacemaker] "Using ldirectord" page question

> Hi,
> I'm trying to set up a redundant load-balancer using pacemaker and
ldirectord and found an example for the configuration on the following page:
> http://www.clusterlabs.org/wiki/Using_ldirectord

> What I don't understand is the following part:
> "This gives you the virtual IP address and ldirectord running together in
a group (ip-lvs) on one node, and the same virtual IP address assigned to
the loopback address on all other nodes. This is necessary to make the
routing work correctly. "

> Why is the configuration of the IP on the lo interfaces necessary for
routing?
> As far as I understand is the VIP only needs to run on the active node
that is also running the ldirectord daemon. Once the failover  happens both
move over to the new active node and the setup should continue to work as
before. Is there something I'm missing here?

> Regards,
>   Dennis