It's because Oracle clusterware will bind them automatically and dynamically. I think we should try to figure out the interface configurations.
First, let's see what interfaces we have now.
[root@primary01 ~]$ ll /etc/sysconfig/network-scripts/ifcfg-*
-rw-r--r-- 1 root root 314 May 30 2016 /etc/sysconfig/network-scripts/ifcfg-eth0
-rw-r--r-- 1 root root 311 May 30 2016 /etc/sysconfig/network-scripts/ifcfg-eth1
-rw-r--r--. 1 root root 254 Jul 22 2014 /etc/sysconfig/network-scripts/ifcfg-lo
But if you list all configuration at run-time, you may see some ghost interfaces. In this case, we can see eth0:1, eth0:4, eth0:5, and eth1:1 are all dynamically registered.
[root@primary01 ~]$ ifconfig -a
eth0 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:79
inet addr:10.34.98.11 Bcast:10.34.98.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe6b:9f79/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:281243 errors:0 dropped:0 overruns:0 frame:0
TX packets:98034 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:329861787 (314.5 MiB) TX bytes:44396484 (42.3 MiB)
eth0:1 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:79
inet addr:10.34.98.111 Bcast:10.34.98.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth0:4 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:79
inet addr:10.34.98.82 Bcast:10.34.98.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth0:5 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:79
inet addr:10.34.98.81 Bcast:10.34.98.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
eth1 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:83
inet addr:10.34.108.11 Bcast:10.34.108.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe6b:9f83/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:87719 errors:2 dropped:2 overruns:0 frame:0
TX packets:103924 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:58723897 (56.0 MiB) TX bytes:82332932 (78.5 MiB)
Interrupt:16 Base address:0x2000
eth1:1 Link encap:Ethernet HWaddr 00:0C:29:6B:9F:83
inet addr:169.254.135.24 Bcast:169.254.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
Interrupt:16 Base address:0x2000
...
In the above configurations:
- eth0 is the Public IP, this is a static interface.
- eth0:0 is the Virtual IP (VIP) of this node.
- eth0:4 is the second SCAN IP address.
- eth0:5 is the third SCAN IP address.
- eth1 is the Private IP, this is a static interface.
- eth1:1 is the HAIP address.
That is to say, the first SCAN IP is located at another node.