Remote "Local Address" of netstat and SCAN listener and VIP on different hosts
- From: Yong Huang <yong321@xxxxxxxxx>
- To: oracle-l@xxxxxxxxxxxxx
- Date: Mon, 23 Apr 2012 12:51:16 -0700 (PDT)
2-node Oracle 11.2.0.1 RAC, RHEL 5.7 x86_64, kernel 2.6.18-274.7.1.el5
One of the 3 SCAN listeners listens on an IP which exists on the other
node of this 2-node RAC.
C:\>nslookup scancs4.<domainname>
...
Name: scancs4.<domainname>
Addresses: 10.111.76.85
10.111.76.84
10.111.76.86
dcsrpcora4a ~ $ ifconfig | egrep '10.111.76.84|10.111.76.85|10.111.76.86'
inet addr:10.111.76.85 Bcast:10.111.76.127 Mask:255.255.255.128
inet addr:10.111.76.84 Bcast:10.111.76.127 Mask:255.255.255.128
dcsrpcora4b ~ $ ifconfig | egrep '10.111.76.84|10.111.76.85|10.111.76.86'
inet addr:10.111.76.86 Bcast:10.111.76.127 Mask:255.255.255.128
The problem is that the 3 IP's, supposedly each backed by one Oracle
SCAN listener, do not all have SCAN listeners listening on them.
Specifically, 10.111.76.84 on node a has no listener, and on node b there
*is* a SCAN listener that claims to be listening on that IP. (Note that
the 4th field of `netstat -an' is "Local Address".)
dcsrpcora4b ~ $ netstat -anp 2>/dev/null | grep 10.111.76.84 <-- this IP exists
on node a
tcp 0 0 10.111.76.84:1521 0.0.0.0:*
LISTEN 15130/tnslsnr
tcp 0 0 10.111.76.70:55578 10.111.76.84:1521
ESTABLISHED 12061/ora_pmon_orac
dcsrpcora4b ~ $ ps -fp 15130
UID PID PPID C STIME TTY TIME CMD
oracle 15130 1 0 Jan27 ? 00:04:40
/u01/app/11.2.0/grid/bin/tnslsnr LISTENER_SCAN3 -inherit
How can a listener process running on its own server (node b) claim to be
listening on an IP which is physically located on a different server (node
a)? On node a, everything looks normal from the OS perspective, and there
actually is a process, named, listening on 10.111.76.84 using port 53.
(Not sure why named uses a virtual interface created by Oracle.)
[root@dcsrpcora4a ~]# netstat -anp | grep 10.111.76.84
tcp 0 0 10.111.76.84:53 0.0.0.0:*
LISTEN 5001/named
udp 0 0 10.111.76.84:53 0.0.0.0:*
5001/named
We know a SCAN VIP can "float" or relocate between the 2 nodes. But at any
give point in time, when netstat says a specific IP is local to a specific
host, that IP must be given by that host (as shown by ifconfig), not by a
different host, regardless what magic Oracle's SCAN listener software does.
Checking with srvctl:
dcsrpcora4a ~ $ srvctl status scan -i 3
SCAN VIP scan3 is enabled
SCAN VIP scan3 is running on node dcsrpcora4a
dcsrpcora4a ~ $ srvctl status scan_listener -i 3
SCAN Listener LISTENER_SCAN3 is enabled
SCAN listener LISTENER_SCAN3 is running on node dcsrpcora4b <-- not dcsrpcora4a!
On another RAC cluster, I tried 'srvctl relocate scan' and 'srvctl
relocate scan_listener'. In both cases, both the SCAN VIP and SCAN
listener are relocated *together* to a different node. It's not possible
to reproduce relocating one but not the other.
I believe to correct the problem we have now, we may just run srvctl
relocate either the VIP (...84) or the SCAN listener (LISTENER_SCAN3). But
I'd like to find out what caused this situation.
Yong Huang
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