Network Planning for ORACLE 11GR2 RAC

In ORACLE 11gR2, the installation of RAC has changed significantly. In the age of 10 GB and 11gR1, the procedure for installing RAC is to first install CRS and then install DB. In the age of 11gR2, crs and asm are integrated and collectively called GRID, you must first install the GRID before you can continue to install the DB. Otherwise, you will be disconnected from the RAC of 11gR2. Next, let's talk about the network planning of ORACLE 11g R2 RAC. Starting from ORACLE 11.2, there are special requirements for network IP addresses and scan ip addresses are added. Therefore, at least four IP addresses are required from 11.2.

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Assume that a server has four NICs: eth0, eth1, eth2, and eth3.
You can bind eth0 and eth2 to bond0. As the public-ip address of RAC, it provides external communication.
Then, bind eth1 and eth3 to bond1 as the private-ip of RAC to provide internal heartbeat communication.
The hosts card on the Server communicates with the backend storage through an optical fiber switch.

Let's take a look at the content in the/etc/hosts file.
10.18.12.140 S1P32 # RAC1 Public
10.18.12.142 S1P32-vip # RAC1 VIP
22.22.22.140S1P32-priv # RAC1 Private

10.18.12.141 S1P33 # RAC2 Public
10.18.12.143 S1P33-vip # RAC2 VIP
S1P33-priv # RAC2 Private

10.18.12.144 catdb-scan # RAC SCAN

1. Let's talk about PUBLIC and VIP first.
Each node in Oracle RAC has a virtual IP address (VIP), which is in the same CIDR block as the public ip address. The vip is attached to the public network interface.
The main difference between VIP and public ip is that VIP is floating while public ip is fixed. When all nodes are running normally, the VIP address of each node is allocated to the public NIC. In the ifconfig command in linux, there are two IP addresses on the public NIC. If one node is down, the VIP of this node will be transferred to the node that is still running. That is, there are three IP addresses on the public NIC of the surviving node.

As shown in the figure, the public ip address is a PUBLIC address bound to a dual-network card. external users access the IP address through VS1.

2. Look at Private in RAC.
Private IP addresses in RAC are used for heartbeat synchronization, which can be ignored directly at the user level. Simply put, this Ip address is used to ensure data synchronization between the two servers, and belongs to the internal communication between RAC. Priv and public should not belong to the same interface.
Another question: can the NICS used for interconnection between two nodes be connected through a cross-line connection?
The RAC document on Metalink recommends that you use a vswitch as the connection to an internal Nic instead of a crossover line, the reason is to avoid deleting the bound protocol because the network adapter checks the link failure status due to the disconnection or restart of the connected node. As a result, the cache merge network will become unavailable.

As shown in the figure, internal communication between the two nodes is performed through the S2 switch.

3. scan ip address in RAC
In 11gR2, the scan ip address appears as a new IP address. The scan ip address is a newly added connection layer between the oracle client and the database. When a client accesses the IP address, connect to the scan ip listener. When the scan ip listener receives the connection request, it forwards the client connection request to the vip listener on the corresponding instance according to the LBA algorithm, this completes the connection process between the client and the server. Simplified as follows:
Client-> scan listener-> local instance
Scan can also be understood as a virtual host name, which corresponds to the entire RAC cluster. The client host can access any node of the Database Cluster by using the scan name. Of course, the accessed nodes are random. oracle strongly recommends configuring resolution SCAN in the round robin mode of DNS Server to achieve load balancing, that is, rotating the IP address corresponding to the SCAN connection ). This is similar to the principle of implementing Load Balancing through the vip and listener loadbalance configurations.

Oracle RAC itself is complex. It may encounter various problems during installation and management, involving OS, RDBMS, Cluster software and network, host, storage and other hardware, to avoid unnecessary problems, clear network planning before installation is very important for the entire architecture and we are willing to share with you.
 

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