IP address used by listener

Question

hi all,
we have 2 IPs (network cards) on one server (hp-ux). oracle db is installed on this server.
The listener PROD is defined in listener.ora using hostname
PROD =
(ADDRESS_LIST =
(ADDRESS= (PROTOCOL= IPC)(KEY= EXTPROCPROD))
(ADDRESS= (PROTOCOL= TCP)(Host= prodhost.prodomain)(Port= 1541))
in /etc/hosts
192.168.1.1 prodhost.prodomain prodhost
172.16.1.1 prodhost.prodomain prodhost
in hosts file only IP is different
my question is how to know which IP address the listener is using??
is there listener command that shows which IP address is used for the listener??
thank you
Edited by: BlueNet on Nov 3, 2010 1:23 PM

Answer 1

Billy  Verreynne  wrote:
BlueNet wrote:
my question is how to know which IP address the listener is using??All local IP addresses usually... depending on what you have in your listener.ora file.
In socket programming, you bind a port to a local IP address. There are 2 primary parameters specified in this - the port to bind too and the IP address to bind too.
Most server s/w does not specify a specific IP address when doing this bind. Instead they use a socket constant called INADDR_ANY - and this binds the port to all IP addresses/interfaces of that server.
You can look at sample C code that describes this at this link.
So how does the Oracle Listener deal with this when binding of port 1521?
This is slightly convoluted (as tested with 10.2).
It uses the IP address only if you specify the IP only in the listener.ora file. E.g.
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.100 )(PORT = 1521))
)So it will not listen on 127.0.0.1 (localhost) or any other IP addresses.
However, when you use the hostname instead, it binds using INADDR_ANY - and will listen on all your server's local IP addresses. E.g.
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = my-hostname.domain.com )(PORT = 1521))
is there listener command that shows which IP address is used for the listener??On Linux/Unix there is a command called lsof (List Of Files). This lists the file handles, and type of handle, of a process. A socket handle is also treated as a file handle. So this command lists socket handles too.
Example:
// listener config
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> cat listener.ora
# listener.ora Network Configuration File:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = my-hostname.domain.com )(PORT = 1521))
// starting the listener
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> lsnrctl start
// finding the listener process
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> ps -fu oracle | grep lsnr | grep -v grep
oracle   19290     1  0 10:21 ?        00:00:00 /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin/tnslsnr LISTENER -inherit
// listing its IP handles in numeric format - note the wildcard next to port 1521
// that indicates it listens to all local IP addresses
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> lsof -ni -p 19290
COMMAND   PID   USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
tnslsnr 19290 oracle    8u  IPv4 8764260      0t0  TCP *:1521 (LISTEN)Now we repeat using an IP address instead:
// the config is for a single IP
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> cat listener.ora
# listener.ora Network Configuration File:
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = 192.168.0.100 )(PORT = 1521))
// we start the listener
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> lsnrctl start
// we find the process id
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> ps -fu oracle | grep lsnr | grep -v grep
oracle   21386     1  0 10:26 ?        00:00:00 /usr/lib/oracle/xe/app/oracle/product/10.2.0/server/bin/tnslsnr LISTENER -inherit
// we lists its IP socket handles - it shows listening on a specific IP for port 1521
/usr/lib/oracle/xe/app/oracle/product/10.2.0/server/network/admin> lsof -ni -p 21386
COMMAND   PID   USER   FD   TYPE  DEVICE SIZE/OFF NODE NAME
tnslsnr 21386 oracle    8u  IPv4 8767359      0t0  TCP 192.168.0.100:1521 (LISTEN)
Billy,
Thanks for posting that. That's a layer of networking I've never gotten to, so was unaware of the "niceties" of specifying servername vs. ip address in the listener.ora.
Very enlightening.