RAC Operational Practices - Expert Oracle RAC 12c - page 79

If a service is not visible in a SCAN listener services output, the service registration to SCAN listener(s) is
incorrect. Similarly, the lsnrctl services command output of a VIP listener will print services as LOCAL SERVER
keyword, indicating that the VIP listener will handle the connection for that service.
SCAN Listener in Second Network (12c)
From version 11.2 and later, it is possible to create a second network, and VIP listeners can be created in the second
network, too. However, SCAN listeners can listen only in the default first network in version 11.2. Version 12c
eliminates that restriction, and it is possible to have SCAN listeners listening on a second network also. By specifying
the listener_networks parameter, SCAN listeners will redirect the connection to VIP listeners within the same
network subnet.
Let us walk through an example of SCAN listener in the second network in version 12c. The following set of
commands adds a network with netnumber 2 in a subnet of 192.168.8.0 (note that first network has 10.7.11.0 subnet).
The next three commands add VIP addresses with -netnumber 2, specifying that these VIP listeners are associated
with the second network. The fourth command adds a listener to listen in port 1521 in these node VIP addresses.
$ srvctl add network -netnum 2 -subnet 192.168.8.0/255.255.255.0
$ srvctl add vip -node rac1.example.com -address rac1vip.example2.com /255.255.255.0 -netnum 2
$ srvctl add vip -node rac2.example.com -address rac2vip.example2.com /255.255.255.0 -netnum 2
$ srvctl add vip -node rac3.example.com -address rac3vip.example2.com /255.255.255.0 -netnum 2
$ srvctl add listener -netnum 2 -endpoints TCP:1522
The following commands add a SCAN name in network 2 with a SCAN name of ebs.example2.com . The second
of the following two commands adds a SCAN listener 3 listening in port 20000, and Grid Infrastructure identifies SCAN
IP addresses by querying DNS for SCAN name ebs.example2.com .
$ srvctl add scan -scanname ebs.example2.com -netnum 2
$ srvctl add scan_listener -listener LISTSCAN -endpoints TCP:20000
Database initialization parameter listener_networks must be modified so that the PMON or LREG process can
register the services to listeners in both networks. The LISTENER_NETWORKS parameter specifies the network
configuration in two parts, the first part specifying the configuration of the first network, named network1, and the
second part specifying the configuration of the second network, named network2. In this example, listener_net1 and
listener_net2 are TNS aliases connecting to VIP listener in local nodes; the remote_listener parameter refers to the
SCAN listeners running in their respective networks specified using EZConnect syntax.
alter system set LISTENER_NETWORKS='((NAME=network1)(LOCAL_LISTENER=listener_net1)
(REMOTE_LISTENER= ebs.example.com : 10000))','((NAME=network2)(LOCAL_LISTENER=listener_net2)
(REMOTE_LISTENER= ebs.example2.com : 20000))';
Consider the following connection string from a user connecting to the second network (possibly a connection
originating from example2.com domain): SCAN listeners will redirect the connection to a VIP listener in the second
network only. Essentially, connection from the second network subnet will remain in the second network subnet and
the network packets may not traverse from one subnet to another subnet. This network demarcation is important,
as a firewall might prevent network packets from crossing over to another domain.
3 Notice the syntax for adding scan_listener does not specify a netnum clause. This appears to be a documentation bug, so refer to
public documentation to verify the syntax.