[mrtg-developers] Mathematical operations on OIDs

[nisha]

Hi Steve,

This solution worked. But now i have a problem when the calcualtion results
in a negative value. 

Lets say [oid1 - (oid2 * 5)] gives a positive value and [oid3 - (oid4 * 10)]
gives a negative value then the rrds are not able to update these values and
hence my graph shows Nan

Have you come across something like this before? Can mrtg can handle this?

Regards,
Nisha



S Shipway wrote:
> 
> This is not possible as you state it; Target line calculations can only be
> done on an OID pair.  However you might achieve it like this:
> 
> Target[targetname]: oid1&oid3:comm. at host - ( oid2&oid4:comm at host * 5 + (
> pseudoZero&oid4:comm. at host * 5 ) )
> 
> Note that the spaces around the brackets and arithmetic signs are
> essential.  'pseudoZero' is a magic MRTG virtualOID that always resolves
> to zero.
> 
> Check the documentation on complex calculated Target lines online at
> www.mrtg.org<http://www.mrtg.org/> or get a copy of the book from
> www.steveshipway.org/book<http://www.steveshipway.org/book>
> 
> Your example below is using oid4x10 in one place but oid4x8 in another but
> I guess that's just a typo.
> 
> Steve
> 
> ________________________________
> From: nisha (via Nabble) [mailto:ml-user+230579-585948030 at n2.nabble.com]
> Sent: Thursday, 27 August 2009 11:02 p.m.
> To: Steve Shipway
> Subject: [mrtg-developers] Mathematical operations on OIDs
> 
> Hi all,
> 
> I want to perform mathematical operations on OIDs in the target line. For
> example, there are 4 oids as shown below:
>         traffic packet
> In oid1 oid2
> Out oid3 oid4
> 
> 
> Now i want to apply the following formula
>         traffic in  = oid1 - (oid2 * 5)
>         traffic out = oid3 - (oid4 * 10)
> 
> My target line in router cfg file is like this:
> Target[targetname]: oid1&oid3:comm at hostname - (oid2 * 5)&(oid4 *
> 8):comm at hostname
> 
> Is this possible in MRTG? Can the router cfg file handle oids with
> mathematical operations?
> 
> 
> 
> 

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