[Pacemaker] How does fail over IP work

Brent Bolin brent.bolin at gmail.com
Wed Mar 23 23:38:29 EDT 2011

Have successfully setup centos 5.5 -

# crm status
Last updated: Wed Mar 23 22:32:40 2011
Stack: openais
Current DC: cluster1 - partition with quorum
Version: 1.0.10-da7075976b5ff0bee71074385f8fd02f296ec8a3
2 Nodes configured, 2 expected votes
2 Resources configured.
Online: [ cluster1 cluster2 ]
 ClusterIP (ocf::heartbeat:IPaddr2): Started cluster1
 WebSite (ocf::heartbeat:apache): Started cluster1

Everything appears to work fine when failing over.  However I don't
understand why

crm configure show
node cluster1 \
attributes standby="off"
node cluster2 \
attributes standby="off"
primitive ClusterIP ocf:heartbeat:IPaddr2 \
params ip="" cidr_netmask="32" \
op monitor interval="30s"
primitive WebSite ocf:heartbeat:apache \
params configfile="/etc/httpd/conf/httpd.conf" \
op monitor interval="1min"
colocation website-with-ip inf: WebSite ClusterIP
property $id="cib-bootstrap-options" \
dc-version="1.0.10-da7075976b5ff0bee71074385f8fd02f296ec8a3" \
cluster-infrastructure="openais" \
expected-quorum-votes="2" \
stonith-enabled="false" \
rsc_defaults $id="rsc-options" \

cluster1 IP is
cluster2 IP is

The cluster fail over IP is

I don't see any IP alias -

[root at cluster1 ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:8B:71:2C
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::20c:29ff:fe8b:712c/64 Scope:Link
          RX packets:20758 errors:0 dropped:0 overruns:0 frame:0
          TX packets:28449 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:2319277 (2.2 MiB)  TX bytes:3419927 (3.2 MiB)

lo        Link encap:Local Loopback
          inet addr:  Mask:
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:584 errors:0 dropped:0 overruns:0 frame:0
          TX packets:584 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:307860 (300.6 KiB)  TX bytes:307860 (300.6 KiB)

[root at cluster1 ~]# ping
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.021 ms
64 bytes from icmp_seq=2 ttl=64 time=0.025 ms

[root at cluster1 ~]# ssh
root at's password:
Last login: Wed Mar 23 22:15:11 2011 from cluster2
[root at cluster1 ~]#

How does this work?

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