How to Configure SCAN and VIPs in Oracle RAC 19c

 

How to Configure SCAN and VIPs in Oracle RAC 19c

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1. What is SCAN and VIP in RAC? (Quick intro)

• SCAN (Single Client Access Name):
• A single name that clients use to connect to the database.
• Behind the scenes, SCAN resolves to three IP addresses (round-robin via DNS or GNS).
• Advantage: No need to change client connection strings if nodes are added/removed.
• VIP (Virtual IP):
• Each RAC node gets a VIP in addition to its public IP.
• If a node fails, its VIP can quickly failover to another node.
• Helps in fast TCP/IP failover without long TCP timeout delays.

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2. Network Requirements

You'll need three networks:

• Public Network (for client/database communication)
• Private Network (for cluster interconnect/heartbeat)
• Optional: Backup Network (for redundancy)

Important IP planning:

IP Type	Needed
Public IPs	1 per node
VIPs	1 per node
Private IPs	1 per node
SCAN IPs	3 total (shared across the cluster)

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3. DNS Setup (for SCAN and VIPs)

Before RAC installation, ensure:

• SCAN Name points to three IP addresses in DNS.
• VIP Names are mapped separately in DNS (or /etc/hosts for non-production setups).

Example DNS Entries:

# SCAN entries (round-robin DNS) testrac-scan.subnet09212030.vcn09212030.oraclevcn.com IN A 10.0.0.98 testrac-scan.subnet09212030.vcn09212030.oraclevcn.com IN A 10.0.0.177 testrac-scan.subnet09212030.vcn09212030.oraclevcn.com IN A 10.0.0.112 # Public IPs testrac1.subnet09212030.vcn09212030.oraclevcn.com IN  A 10.0.0.127 testrac2.subnet09212030.vcn09212030.oraclevcn.com IN  A  10.0.0.158 # VIPs testrac1-vip.subnet09212030.vcn09212030.oraclevcn.com  IN  A  10.0.0.36 testrac2-vip.subnet09212030.vcn09212030.oraclevcn.com  IN  A  10.0.0.178

 

Note:

• SCAN should not resolve to a single IP — must have three IPs.
• VIPs should be in the same subnet as the public IPs.

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4. /etc/hosts Example (if not using DNS)

# Public IPs 10.0.0.127 testrac1.subnet09212030.vcn09212030.oraclevcn.com testrac1 10.0.0.158  testrac2.subnet09212030.vcn09212030.oraclevcn.com  testrac2   # VIPs 10.0.0.36 testrac1-vip.subnet09212030.vcn09212030.oraclevcn.com testrac1-vip 10.0.0.178  testrac2-vip.subnet09212030.vcn09212030.oraclevcn.com  testrac2-vip   # Private Interconnect 192.168.16.18 testrac1-priv.subnet09212030.vcn09212030.oraclevcn.com testrac1-priv 192.168.16.19  testrac2-priv.subnet09212030.vcn09212030.oraclevcn.com  testrac2-priv   #Scan IPs 10.0.0.98         testrac-scan.subnet09212030.vcn09212030.oraclevcn.com 10.0.0.177      testrac-scan.subnet09212030.vcn09212030.oraclevcn.com 10.0.0.112      testrac-scan.subnet09212030.vcn09212030.oraclevcn.com

 

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5. During Grid Infrastructure Installation

When you install Grid Infrastructure:

• Installer will prompt for SCAN name.
• Installer will auto-detect SCAN IPs based on DNS.
• It will also ask for:
• Public Interface
• Private Interface
• VIP names for each node.

✅ Oracle Clusterware will configure and manage SCAN listeners and VIP listeners automatically after installation.

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6. Post-Installation Checks

After installation:

• Check SCAN listeners:

$srvctl config scan

[oracle@testrac1 ~]$ srvctl config scan SCAN name: testrac-scan.subnet09212030.vcn09212030.oraclevcn.com, Network: 1 Subnet IPv4: 10.0.0.0/255.255.255.0/enp0s5, static Subnet IPv6: SCAN 1 IPv4 VIP: 10.0.0.112 SCAN VIP is enabled. SCAN 2 IPv4 VIP: 10.0.0.177 SCAN VIP is enabled. SCAN 3 IPv4 VIP: 10.0.0.98 SCAN VIP is enabled.

 

$srvctl config scan_listener

[oracle@testrac1 ~]$ srvctl config scan_listener SCAN Listeners for network 1: Registration invited nodes: Registration invited subnets: Endpoints: TCP:1521 SCAN Listener LISTENER_SCAN1 exists SCAN Listener is enabled. SCAN Listener LISTENER_SCAN2 exists SCAN Listener is enabled. SCAN Listener LISTENER_SCAN3 exists SCAN Listener is enabled.

 

• Check VIPs:

[oracle@testrac1 ~]$ srvctl config nodeapps Network 1 exists Subnet IPv4: 10.0.0.0/255.255.255.0/enp0s5, static Subnet IPv6: Ping Targets: Network is enabled Network is individually enabled on nodes: Network is individually disabled on nodes: VIP exists: network number 1, hosting node testrac1 VIP Name: testrac1-vip.subnet09212030.vcn09212030.oraclevcn.com VIP IPv4 Address: 10.0.0.36 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes: VIP exists: network number 1, hosting node testrac2 VIP Name: testrac2-vip.subnet09212030.vcn09212030.oraclevcn.com VIP IPv4 Address: 10.0.0.178 VIP IPv6 Address: VIP is enabled. VIP is individually enabled on nodes: VIP is individually disabled on nodes: ONS exists: Local port 6100, remote port 6200, EM port 2016, Uses SSL true ONS is enabled ONS is individually enabled on nodes: ONS is individually disabled on nodes:

 

You should see VIPs and SCAN listeners running fine.

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7. Troubleshooting Tips

• If SCAN listeners aren’t working, check:
• DNS settings (or /etc/hosts)
• Firewall rules blocking SCAN IPs
• Network interface binding issues
• If VIP fails to start:
• Ensure the VIP is in the correct subnet.
• Check the public network card configuration.