Forum Discussion

mnagel's avatar
mnagel
Icon for Professor rankProfessor
9 years ago

custom speed for interfaces

In some cases, it is important to be able to alter the speed of an interface (speed up or down or both) to accurately reflect the connected device speed (which itself may be opaque, like a cable mo...
answered
Steve_Francis's avatar
Steve_Francis
Former Employee
9 years ago

So the only requirement for this is to have some way to know what the interfaces 'real' speed is. If you can get the Bandwidth description via SNMP (which I could not find an OID for), then it's easy.

Add a datapoint (say, 'RealSpeed') that gets that speed via the right OID to the Interfaces datasource. 

Then change the Utilization datapoint expression from this:

InOctets*8/if(lt(BasicSpeed,4294967295),BasicSpeed/1000000,Speed)/1000000*100 (which says divide inOctets *8 by BasicSpeed, if BasicSpeed is less than 4294967295, else by Speed)

to

InOctets*8/if(un(RealSpeed),if(lt(BasicSpeed,4294967295),BasicSpeed/1000000,Speed)/1000000*100,RealSpeed) (which says divide InOctets * 8  by RealSpeed, unless RealSpeed is unknown - else use the original expression.) This assumes that the OID reports nothing if that bandwidth description is not set.

 

If there is no OID to get the 'real' bandwidth, you will be able to manually set a property on the instance level where you can define the real bandwidth, and then you could use the property in the expression.  Instance level properties are being developed right now, so should be released within 3 months.