Database Reference
In-Depth Information
Cluster Interconnect
Clusterware uses cluster interconnect for exchanging messages such as heartbeat communication, node state change,
etc. Cache fusion traffic uses cluster interconnect to transfer messages and data blocks between the instances.
Both database and ASM instance communicate via cluster interconnect.
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in this chapter, the terms “cluster interconnect” and “private network” are used interchangeably, but “cluster
interconnect” refers to the configuration in oracle Clusterware and “private network” refers to the network configuration
in a database server.
Note
Clusterware captures the private network configuration details in OCR (Oracle Cluster Registry) and in an
XML file. The command
oifcfg
will print network configuration details. As shown in the following output, subnet
172.18.1.x and 172.18.2.x are configured for cluster_interconnect. IP addresses for private network will be in the range
of 172.18.1.1 - 172.18.2.255 in all nodes.
$ oifcfg getif
eth1 10.18.1.0 global public
eth2 10.18.2.0 global public
eth3 172.18.1.0 global cluster_interconnect
eth4 172.18.2.0 global cluster_interconnect
In this cluster node, IP address 172.18.1.13 is configured on the eth3 interface and IP address 172.18.2.15 is
configured on the eth4 interface.
$ ifconfig -a |more
...
eth3: ..<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 4
inet 172.18.1.13 netmask ffffff00 broadcast 172.18.1.255
...
eth4: ..<UP,BROADCAST,RUNNING,MULTICAST,IPv4> mtu 1500 index 4
inet 172.18.2.15 netmask ffffff00 broadcast 172.18.2.255
A primary requirement of private network interface configuration is that an IP address configured in the private
network interface must be a non-routable interface. A non-routable IP address is visible only in a local network, and
the packets destined to those non-routable addresses are guaranteed to be within a switch/router; hence, packets to
those destinations will not be routed to the Internet. Communication between two computers within a default home
network is a classic example that will help you to understand non-routable IP addresses.
7
The RFC 1918 standard
specifies the following IP address ranges are non-routable IP addresses.
10.0.0.0 - 10.255.255.255
172.16.0.0 - 172.31.255.255
192.168.0.0 - 192.168.255.255
7
The example of home networks will help to clear up any confusion about private networks. Network Address Translation (NAT) plays a
critical role in accessing public IP addresses from private IP address spaces. For example, a home network router creates a private
address space. Even though home routers will usually have just one public IP address, many computers are connected to that router, and
many computers can access external websites through the router. The router will translate private IP address to a port and modify return
address as the public address of the router. Using the router translation table, return packets are delivered to the correct port and hence the
correct computer.
