Database Reference
In-Depth Information
Table 29-1 summarizes the TNS Listener's IP address binding behavior under all situations
which may arise. Note that the TNS Listener's behavior for boot IP address, non-boot IP
address or host name, and service IP addresses or host name is identical, irrespective of the
option
IP=FIRST
. In other words,
IP=FIRST
solely has an impact when the system's host name is
used in
listener.ora
.
Table 29-1.
TNS Listener IP Address Binding
HOST Setting
in listener.ora
IP=FIRST
Boot IP
Address
Other Non-Boot IP Address
or Service IP Address (IP Aliasing)
Loopback
Address
System host name
(maps to boot IP address)
yes
yes
no
no
System host name
(maps to boot IP address)
no
yes
yes
yes
Boot IP address
no
yes
no
no
Non-Boot IP address/host
name
no
no
no
no
Service IP
address/host name
no
no
no
no
The first row of the table represents the TNS Listener's behavior when a system's host
name is used in the configuration file
listener.ora
and
IP=FIRST
is set. Columns 3-5 indicate
the IP address binding behavior under the settings in columns 1 and 2. The value “yes” means that
the TNS Listener does bind to the type of IP address indicated in the table's column heading. Thus,
the TNS listener binds solely to the boot IP address under the settings depicted in the first row.
Lessons Learned
This chapter investigated the TNS Listener's binding to IP addresses on multihomed systems
as well as its use of the loopback adapter. Several undocumented aspects were found:
When assigned a system's host name, the TNS Listener uses
INADDR_ANY
and thus can be
reached from any network as well as via the loopback adapter, which always has the IP
address 127.0.0.1.
When assigned the boot IP address or a non-boot IP address or host name, the TNS
Listener does not use
INADDR_ANY
, but instead binds specifically to the address assigned.
It also refrains from using the loopback adapter.
When the op ion
IP=FIRST
is enabled, the TNS Listener binds specifically to the IP address,
which the configured host name resolves to and cannot be reached from any other IP
address including the loopback address. This option is relevant only if the system's host
name is assigned to the parameter
HOST
in
listener.ora
.
