This is typical behavior.

On most systems, the routing of each packet is determined when the
packet is about to be sent.  Just because it comes in a NIC, does't mean
it will response will respond through the same NIC.
        
Since you have multiple interfaces to the same logical network, the
determination of which on it will be sent out, will be determined by
anyone of multiple factors.  The instance number of the NICs.  The IP
addresses of the network interfaces.  Order of routing table entries.
The only way to be sure is to peruse the source code.


-----Original Message-----
From: veritas-bu-bounces AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-bounces AT mailman.eng.auburn DOT edu] On Behalf Of Crowey
Sent: Thursday, March 17, 2011 10:08 PM
To: VERITAS-BU AT MAILMAN.ENG.AUBURN DOT EDU
Subject: [Veritas-bu] NetBackup Not Using Backup NIC

Gidday, I'm trying to troubleshoot some really bad performance issues
when writing to disc for NetBackup differentials, and as part of that
process I noticed that NetBackup is not using the backup NIC I have
configured on our main server.

Our main server has two NICs configured, eth0 on 172.20.10.23 and eth2
on 172.20.10.24.  In DNS I have eth0's address resolving to server, and
eth2's address resolving to server-backup.

I have NetBackup configured to connect to the address server-backup.
And in the Admin Console | Host Properties | Clients I can connect to
the server - ostensibly via the configured DNS address of server-backup.

I can ping both addresses on the Master/Media NetBackup server as well
as the server itself.  However if I do a ifconfig eth0/2 on the server
in question I get this ...

  eth0      Link encap:Ethernet  HWaddr 00:14:4F:0D:82:92  
            inet addr:172.20.10.23  Bcast:172.20.10.255
Mask:255.255.255.0
            inet6 addr: fe80::214:4fff:fe0d:8292/64 Scope:Link
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            RX packets:126134922 errors:0 dropped:0 overruns:0 frame:0
            TX packets:249411328 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000 
            RX bytes:46698652928 (43.4 GiB)  TX bytes:289231929457
(269.3 GiB)
            Base address:0x8800 Memory:85b80000-85ba0000 

  eth2      Link encap:Ethernet  HWaddr 00:14:4F:0D:7E:FA  
            inet addr:172.20.10.24  Bcast:172.20.10.255
Mask:255.255.255.0
            inet6 addr: fe80::214:4fff:fe0d:7efa/64 Scope:Link
            UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
            RX packets:197097 errors:0 dropped:0 overruns:0 frame:0
            TX packets:11 errors:0 dropped:0 overruns:0 carrier:0
            collisions:0 txqueuelen:1000 
            RX bytes:92088745 (87.8 MiB)  TX bytes:782 (782.0 b)
            Base address:0xc800 Memory:b3d80000-b3da0000 

Clearly eth2 (server-backup) is receiving OK, but nothing is going back
out.

Any ideas what I can do to resolve this? - I'm sure its probably
something stupid, but I'd be grateful for any advice on this matter.

(I'm running RHEL AS 4.6 x86_64 by the way)

Cheers
John

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