This is rather silly, but I lost some time with it, so I thought to put it in a blog post as it might be useful to others. Ok, a few days ago I took over an existing cacti installation; I was working to improve it and bring in some other stuff I always do in a cacti installation (note to self, I should really put some blog posts about cacti templates I use, as that will definitely save me some time in the future). One problem I noticed was that there was a traffic interface graph that was wrong when it was going over 114Mbps. I knew what the problem was and it should have been a quick fix.

All I had to do was to change from regular 32-bit counters to 64-bit counters and increase the maximum value to 1M. I have done that, but to my surprise the graph stopped working completely for the respective interface. So I had to dig into it, and debug the problem. I was able to see that the cacti poller snmp query was failing and returning:
Error in packet
Reason: (noSuchName) There is no such variable name in this MIB.
Failed object: IF-MIB::ifHCInOctets.10124

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