How to Configure SCAN and VIPs in Oracle RAC 19c

 

How to Configure SCAN and VIPs in Oracle RAC 19c

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.

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)

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.

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

 

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.

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.

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.

 

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