Automatic Ethernet Failover Using Virtual IP Addressing

Marc Vadeboncoeur, iTech Solutions

Do you have a “backup” for your IBM i system’s Ethernet line in the event that it fails?  If you don’t, did you know that you can configure an automatic failover line quickly and easily in IBM i?

Virtual IP Addressing (a.k.a. “VIPA”) is a capability that has existed on IBM i for quite some time, but surprisingly many shops don’t know about it, or, they are aware of it but don’t realize how easy it is to configure and the terrific redundancy it can quickly & easily provide.

In our services practice here at iTech it is very rare that we see an Ethernet adapter in an IBM i system fail, however, Ethernet switch failures can be a common occurrence.  If you have an unused Ethernet port on your system (as many installations do) and you have another switch in your data center that is on the same network, adding automatic redundancy for your current primary Ethernet connection to your network to guard against a primary switch failure is a snap, and here’s how you do it.

In this configuration example, we assume that you have free/unused Ethernet port available on your system and another switch on the same network that you can attach that unused port to via a simple Ethernet cable connection.  First, determine the “resource name” that your system has assigned to the unused Ethernet port that you wish to use for your failover redundant connection, this can be done by using the command WRKHDWRSC *CMN and looking for a resource name beginning with the letters “CMN..” with the text “Ethernet Port”.  Most Ethernet adapters in use have 4-ports and are installed with the ports aligned vertically and the top port is the 1st port listed for the adapter on the WRKHDWRSC *CMN display, the 2nd port down from the top in the 2nd port listed, etc. so it’s easy to determine the resource name to use, in this example we assume the resource name for the unused port that you are going to use is “CMN03”.

The configuration steps we will use are as follows:

  1. Create a new Ethernet line description and TCP/IP interface for the unused port on the Ethernet card that we will use (using resource name “CMN03” in our example)
  2. Create a new TCP/IP interface that will use the existing (current) line description
  3. Attach to the system with Navigator for i using one of the new TCP/IP interfaces
  4. Delete the current production TCP/IP interface
  5. Create a new virtual IP address interface with the current production IP address
  6. Change the two physical IP interfaces to associate them with the new virtual IP address interface and start the new virtual IP interface

Create a new Ethernet line description and TCP/IP interface for the unused port on the Ethernet card that we will use (using resource name “CMN03” in our configuration example)

Signon to IBM Navigator for i and go to Network/TCP/IP Configuration/IPv4/IPv4 Interfaces and click the Actions drop-down button and select New Interface/Local Area Network to invoke the LAN interface wizard and take all the defaults until you get to the New IPv4 Interface – Resource screen and select the “CMNxx” resource name for the Ethernet card port number you want to use for the new line (“CMN03” in our example below) and click the Next button.

 

Select the Create a new line radio button and click the Next button

Enter-in the desired values for the new Ethernet line name and description and click the Next button until you get to the New IPv4 Interface – Settings screen

Enter-in a static IP address (that’s unused on your network) and the appropriate subnet mask value and some descriptive text as shown below and click the Next button until you get to the New IPv4 Interface – Summary screen

Click the Finish button and the wizard will create the new Ethernet line description and TCP/IP interface for the backup Ethernet link you will be using

Create a new TCP/IP interface that will use the existing (current) line description

Go to Network/TCP/IP Configuration/IPv4/IPv4 Interfaces and click the Actions drop-down button and select New Interface/Local Area Network to invoke the LAN interface wizard and take all the defaults until you get to the New IPv4 Interface – Resource screen and then select the List by lines radio button and then select the radio button alongside the line description for the existing production Ethernet line that you have been using (“ETHLINE” in our example) and then click the Next button and the screen below will appear, enter-in a static IP address (that’s unused on your network) and the appropriate subnet mask value and some descriptive text as shown below and click the Next button until you get to the New IPv4 Interface – Summary screen

Attach to the system with Navigator for i using one of the new TCP/IP interfaces

Logoff your current Navigator for i session and re-start the session using the new system address that you just created above (172.29.6.200 in our example)

Delete the current production TCP/IP interface

NOTE: This step needs to be done when no one is using the system as it will temporarily bring down the current production IP address being used for your system!

Signon to IBM Navigator for i at the new address as described above and go to Network/TCP/IP Configuration/IPv4/IPv4 Interfaces and this screen will appear showing the following:

  • The existing production TCP/IP address of the system (172.29.6.83 in our example)
  • The new TCP/IP interface we created in the steps above to use the new backup Ethernet line (172.29.6.199)
  • The new TCP/IP we created in the steps above to use the existing production Ethernet line (172.29.6.200)

Right-click on your current production Ethernet interface (172.29.6.83 in our example) and click Stop in the popup window that appears to stop the interface

Right-click again on your current production Ethernet interface (172.29.6.83 in our example) and click Delete in the popup window that appears to delete the interface

Create a new virtual IP address interface with the current production IP address

Click the Actions button at the top and select New Interface/Virtual IP and the New IPv4 Interface – Welcome screen will appear, click the Next button and then fill-in the screen below with the IP address that is the normal production TCP/IP address for your system and a subnet mask value of 255.255.255.255 (note that the subnet mask MUST be 255.255.255.255 because you are creating a virtual IP address interface)

Click the Next button until the New IPv4 Interface – Summary screen below appears and then click the Finish button to create the virtual IP interface

Change the two physical IP interfaces to associate them with the new virtual IP address interface and start the new virtual IP interface

Stop the IP interface that you are currently NOT using with your current Navigator for i session (in our example we are currently attached to IP address 172.29.6.200, so we will stop 172.29.6.199)

Right-click on the interface you just stopped and select Properties in the pop-up menu and then click the Advanced tab on the left and you’ll see this screen, for “Associated local interface” select the new virtual IP interface we created in the steps above (172.29.6.83 in our example) and click OK

 

 

 

 

 

 

 

Start interface you just changed (172.129.6.199 in our example)

Now logoff your current Navigator for i session and log back on using the IP address you just changed above (172.16.29.199 in our example)

Signon to IBM Navigator for i at the new address as described above and go to Network/TCP/IP Configuration/IPv4/IPv4 Interfaces and this screen will appear showing the following:

  • The existing production TCP/IP address of the system (172.29.6.83 in our example)
  • The new TCP/IP interface we created in the steps above to use the new backup Ethernet line (172.29.6.199)
  • The new TCP/IP we created in the steps above to use the existing production Ethernet line (172.29.6.200)

Stop the IP interface that you are currently NOT using with your current Navigator for i session (in our example we are currently attached to IP address 172.29.6.199, so we will stop 172.29.6.200)

Right-click on the interface you just stopped and select Properties in the pop-up menu and then click the Advanced tab on the left and you’ll see this screen, for “Associated local interface” select the new virtual IP interface we created in the steps above (172.29.6.83 in our example) and click OK

Start interface you just changed (172.129.6.199 in our example)

Start the interface for the virtual IP address that we created in the steps above (172.129.6.83 in our example) and the virtual IP address configuration is now complete!  The production IP address of your system (172.29.6.83 in our example configuration) is now a virtual IP address that will use one of the physical Ethernet lines on your system and automatically fail over to the other Ethernet line should a line failure occur!

Using virtual IP addressing on your IBM i system is an easy, quick, and FREE way of greatly increasing your system’s resiliency against a network Ethernet connection failure.  The ideal scenario for the highest level of redundancy/resiliency is to use two Ethernet ports that are on different physical Ethernet cards with each connection plugged-into a different Ethernet switch, this will protect your system’s network connectivity against Ethernet card failure and network switch failure.

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