A null, also known as Blackhole, is a routing table entry that discards a matching packet without sending it further. It is mainly used for preventing/ blocking an unwanted IP to attack your system. It drops the IP using IPtables. for instance, if you want to block an IP address 192.168.0.1, you can write the command:
# ip route add blackhole 192.168.0.1/32
your system will now drop all packets coming from 192.168.0.1
If we have two network interfaces, eth0 and eth1 and we want it to be shown in a single bond as bond0, we need to first create a config file with the name bond0. The network configuration in Linux stores files in etc/sysconfig/network-scripts/ directory.
The work parameters must be set as follows:
DEVICE=bond0 IPADDR=192.168.1.20 NETWORK=192.168.1.0 NETMASK=255.255.255.0 USERCTL=no BOOTPROTO=none ONBOOT=yes
The IP address must be replaced with your actual setup.
Open eth0 and eth1 configuration files
# vi /etc/sysconfig/network-scripts/ifcfg-eth0
# vi /etc/sysconfig/network-scripts/ifcfg-eth1
Modify the parameters as follows: DEVICE=eth0 USERCTL=no ONBOOT=yes MASTER=bond0 SLAVE=yes BOOTPROTO=none DEVICE=eth1 USERCTL=no ONBOOT=yes MASTER=bond0 SLAVE=yes BOOTPROTO=none
Save and close the file.
Now load the bond driver/module when the channel bonding interface is brought up. The kernel configuration files are also modified using # vi /etc/modprobe.conf
Add these lines : alias bond0 bonding options bond0 mode=balance-alb miimon=100
Test configuration using these two steps:
Firstly, load the bonding module:
# modprobe bonding
Restart the network to see bond0 interface:
# service network restart
Both Nic's should now be working as one