I am in the situation where I have a number of CentOS Linux servers which all have two NIC interfaces. Currently one of these interfaces is used for internal communication, the other is used for external (internet) communication. Both of the NIC's are connected to the same switch.
My intention is to move both of these tasks to the first NIC and assigning it both an internal and external IP. Doing this will free the second NIC from all of its tasks, which then will be available for being connected to a second (back-up) switch.
The second NIC should the also receive an internal and a external IP address. My question is this: What should I do regarding the IP addressing on the second NIC? When the first switch or NIC breaks is there a way to automatically assign the IP info of NIC1 to NIC2? Or could I always give the the same IP information and let the switches work out the best route? What are proven techniques to accomplish this?
Best Answer
In Linux, this is called a bonded ethernet interface.
The steps here are for Red Hat Linux and hopefully will be similar for other Linux distributions:
Step 1. Create bond0 - ethernet card
#vi /etc/sysconfig/network-script/ifcfg-bond0
Step 2. /etc/sysconfig/network-script/ifcfg-eth0
Step 3. /etc/sysconfig/network-script/ifcfg-eth1
Step 4 /etc/modprobe.conf
mode=1
means active/passive, andmiimon=100
millisecond ping or checks for update.Step 5. Restart the service.