SNMP memory usage

Hello, I am trying to load balance RDP (TCP port 3389) users across Windows2K3 WTS servers based on resource usage. One of the key metrics that I want to base the loadbalancing decision on is physical memory used (.1.3.6.1.2.1.25.2.3.1.6.4 => PhysicalMemoryUnitsUsed) However, the F5 F1500 Big IP the only OID being gathered is .1.3.6.1.2.1.25.2.2.0, which is the total physical memory on the box.

 

 

It would seem that since I have the OID for the PhysicalMemoryUnitsUsed (above) that I could just use a variable to query that OID. However, the OID for the PhysicalMemoryUnitsUsed varies between nodes based on other factors such as network mapped drives and I'm sure there are other factors that might also affect the OID but the point I want to make is it is not a static value.

 

 

Is there a way that I am not aware of to consistently and accurately gather the PhysicalMemoryUnitsUsed from each of the nodes regardless of any factor the would vary the OID? This is a key metric for load balancing and I would assume that I am not the only person wanting to use this metric to make load balacing decisions.

 

 

Also, although the servers are currently homogenous i.e, same platform and amount of memory and so forth, I would like to be able to make the laod balancing decision based on the amount of physical memory left on the box or the ratio of PhysicalMemoryUnitsUsed/TotalPhysicalMemory. This way I can add newer servers with more memory to the cluster or add memory to one of the current nodes and the Big IP box will continue to load balance appropriately. Thanks.