Various IP-PUBLIC-VIP-Private-scan ip addresses in RAC

Each node in various IP-PUBLIC-VIP-Private-scan ip 1, PUBLIC, and VIPOracle RAC in RAC has a virtual IP address (VIP), which is in the same network segment as the public ip. 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. The role of VIP: VIP does not allow user requests to be forwarded to the instance. However, it allows users to connect to IP addresses and cannot connect to the listener. This allows users to quickly receive connection error messages. Quickly switch to a normal node. ######################################## ##### 2. Check that the Private IP in the Private RAC in RAC is used for heartbeat synchronization, this 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. in 11gR2, the scan ip address in RAC appears as a new IP address. The scan ip address is actually a new connection layer between the oracle client and the database, when a client accesses the client, it connects to the scan ip listener. When the scan ip listener receives the connection request, the client's connection request is sent according to the LBA algorithm, the vip listener is forwarded to the corresponding instance to complete the connection process between the client and the server. Simplified as follows: client-> scan listener-> local instance can also regard scan 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 the 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.