Cloverleaf and Multiple IP’s Assigned to Server

[Tim Malaney]

We are currently running Cloverleaf version 6.0.2.0  on Linux.We are being required to change the IP of our Cloverleaf server. Our Server Engineers have stated that they may be able to place a second network card in the server with the new IP and allow for a gradual transition to the new IP. Has anyone hear of this being done?

Topic

[James Cobane]

Tim,

You may also want to consider using DNS vs IP for reference by external systems; that way they are agnostic to the actual IP address.

[Tim Malaney]

Thanks – most are DNS. We have a couple applications that are IP and the vendors will only make the change off hours for $$$.

[David Barr]

We have two IP addresses for our Cloverleaf servers: one that’s associated with the actual server, and another one that is for interface connections. We used to fail over the second address when we were doing HA on HPUX. Now we’re using Linux and VMWare, and we don’t have a secondary server set up. We rely on VMWare for hardware redundancy. We still use the second IP address for upgrades. We stage a server with the new version and start listening on the published IP address when we’re ready to cut over to the new server.

We’ve got a disaster recovery project underway, so we may have to change things slightly when we figure out how we are going to do disaster failover.

[Tim Malaney]

David, not sure I follow but it seems interesting. Do you have 1 physical server with two addressable IP’s? Can a sending system connect to either IP and a Cloverleaf thread? If so, how is the Cloverleaf connection being made – on the port?? Is it the port/IP that makes it unique?

Thanks

[Paul Glezen]

Network interfaces support multiple IP addresses.  Often an IP assigned after the first IP is considered a “secondary IP”.  There can be multiple secondaries.  The interface will respond to ARP requests for either IP.

I suspect the bigger question is how do you eventually remove the old IP (otherwise why bother moving in the first place).  If you have just a few clients, it’s easy to determine which client is using which IP.  Remove the old secondary IP when all your clients have migrated to the new IP.

Another factor is to which IP does your Cloverleaf servers bind.  You could have them all bind to 0.0.0.0 so that all inbound IP traffic is considered.  But some people prefer each server bind to a single IP.  In the interim you’ll have some servers bind to the primary, some to the secondary.  After you have all Cloverleaf servers binding to the new IP, you can remove the secondary IP from the network interface.

Disclaimer: I have no Cloverleaf-specific experience with this.  But I’ve done this kind of thing with other network devices used as data center application proxies.

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