I have not been on a Linux server in ages. Recently, I noticed the use of PREFIX versus NETMASK for IP configuration.
Basically PREFIX=16 is the same as NETMASK 255.255.0.0 and PREFIX=24 is the same as NETMASK 255.255.255.0
Which one is your server using?
[oracle@rac02 ~]$ uname -an Linux rac02.localdomain 2.6.39-200.24.1.el6uek.x86_64 #1 SMP Sat Jun 23 02:39:07 EDT 2012 x86_64 x86_64 x86_64 GNU/Linux [oracle@rac02 ~]$ cat /etc/sysconfig/network-scripts/ifcfg-eth0 NAME="System eth0" DEVICE="eth0" TYPE="Ethernet" BOOTPROTO=none ONBOOT=yes NM_CONTROLLED="yes" IPV4_FAILURE_FATAL=yes IPV6INIT=no GATEWAY=172.16.0.1 DNS1=172.16.0.1 DEFROUTE=yes PREFIX=16 #rac01 #IPADDR=172.16.1.51 #HWADDR=08:00:27:D4:1A:98 #rac02 HWADDR=08:00:27:35:2D:54 IPADDR=172.16.1.52 [oracle@rac02 ~]$ cat /etc/sysconfig/network-scripts/ifcfg-eth1 NAME="System eth1" DEVICE="eth1" TYPE="Ethernet" BOOTPROTO=none ONBOOT=yes NM_CONTROLLED="yes" IPV4_FAILURE_FATAL=yes IPV6INIT=no DEFROUTE=yes GATEWAY=172.16.0.1 PREFIX=24 #rac01 #HWADDR=08:00:27:33:4C:DF #IPADDR=10.10.10.71 #rac02 HWADDR=08:00:27:BD:53:A7 IPADDR=10.10.10.72
Reference:
http://www.netfilter.org/documentation/HOWTO/networking-concepts-HOWTO-4.html
