>>> <[EMAIL PROTECTED]> 04/01/04 02:54AM >>> >Hello to all, > >I need some help with MRTG. > >I'm monitoring four high speed interfaces and I want to measure the >Aggregate of 2 x firewall external interfaces minus aggregate of 2 x >firewall internal, like so:- > >[target]: 1:[EMAIL PROTECTED] + 2:[EMAIL PROTECTED] - >3:[EMAIL PROTECTED] + 4:[EMAIL PROTECTED] > >However the graph should be flat (or close to flat) but what I'm actually >getting is (1+2) (3+4), not (1+2)-(3+4) effectively double the internal and >external graphs, anyone have any ideas? > >Regards. > >John
To paraphrase Monty Python - "You need to get to TWO OIDs in each intended target, not one, not three, two, only after you have completed one. Your goal is to get TWO OIDs." So, MRTG is doing more than I would expect it to do. If your goal is to subtract the sum of 3 & 4 from the sum of 1 & 2, you need to do some additional math. Do you want one line on your graph? If so, you'll need to do one of at least two things to get there. 1. Find an OID that always returns 0 and incorporate that into your equation. 2. Write an external script to do the math and not worry about the OID. Either way, you need to provide an expression similar to this: target: OID1&OID2 It can be in a form like so: target: OID1&0 + OID2&0 - OID3&0 - OID4&0 This will result in adding OIID1 and OID2, then subtracting the value of OID3 and OID4. (1+2) - (3+4) is the same as 1 + 2 - 3 - 4. Remember MRTG doesn't do negative values. Paul Please add -- Unsubscribe mailto:[EMAIL PROTECTED] Archive http://www.ee.ethz.ch/~slist/mrtg FAQ http://faq.mrtg.org Homepage http://www.mrtg.org WebAdmin http://www.ee.ethz.ch/~slist/lsg2.cgi
