Hello,
we are using MRTG to measure throughput connections between LAN equipment, and bbmrtg.pl to report the status to Hobbit / Xymon. bbmrtg.pl is extended to optionally check the status of a connection too, and report a 'red' status if the connection is down. We have found this a useful feature, as it detects link problems even in case redundancy in the network hides the problem.
bbmrtg.pl is extended to take some special action if (A) variable bb*chklink is defined and (B) at the same time no input is received, thus 0 bytes per second, and almost no output is sent. There are two cases: if bb*chklink is negative, this condition is sufficient to set the status of the connection to 'red'. If bb*chklink is positive, it is assumed to be the ifIndex of the interface. Using SNMP, the current status of the interface is retrieved. If the status is "down", the connection status is set to 'red'. The small amount of output allowed takes care of some L2 protocols which are almost always active, such as STP or CDP.
Note that this condition cannot be checked with the original version of bbmrtg.pl. That version cannot check for the condition that both input *and* output is (almost) zero.
Attached is the list of modifications in bbmrtg.pl.
Kind regards, Wim Nelis.
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