Siemens S7-400 FH Redundancy

[booger]

I am looking to understand how Siemens implements redundancy in their S7-400 series PLCs. Specifically, we provide a DCS that speaks modbusTCP, and need to interface to a redundanct siemens plc.

I have spent a day or so slogging through the prodigous siemens online documentation, and can't really find anything that clearly describes the standard redundancy configuration. I would like to know if for example the siemens configuration for redundant is similar to ControlLogix where the redundant racks look like a single IP address, and they swap the IP address on failover.

Any help would be appreciated.

 

[booger]

Siemens' Redundancy

Not that anyone else has had or will have this question - but I got the answer from Siemens support so I will post here.

The S7-400H series is what I was referrring to. This is Siemens hot-backup configuration. It turns out that Siemens does there redundancy differently than everyone else. ControlLogix redundancy is handled (from the ethernet standpoint) so that the redundant node appears as a single IP address. The redundancy scheme switches the IP address to whichever side is the running side.

Siemens allows you to talk to either side, the running side or the backup and their redundancy propogates the data across. Siemens expects that if you are configuring a redundant node to exist on a network, that each side of the redundant pair be configured with a separate IP address. You can however configure both sides with the same IP address so long as they are not on the same ethernet network.

I suspect that part of the reason there are so few questions about Siemens is that there phone support is excellent.