Extension of bbmrtg.pl: check on link down

[W.J.M. Nelis]

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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