Robert Bentley .NET

This is more a confused ramble than a blog entry.

I use a Cacti installation (www.cacti.net) to poll the SynergyWorks switches via SNMP and generate traffic graphs on a per-port basis. Until recently only 100Mbps ports were used, so 32bit SNMP counters were fine. As traffic grew however, I had to purchase various all-gigabit Dell PowerConnect 5324 switches. Graphing these showed the traffic bunny-hop between 0Mbit and 100Mbit when traffic flowed at a rate higher than ~ 100Mbps. This was clearly the 32bit counter rolling over - so I switched over to 64-bit counters - problem solved (i thought).

Forward fast 6 months, when I purchase a HP ProCurve 2824 Gigabit switch for our Telehouse East core. This was setup in the same way, SNMP enabled and polled using 64-bit counters via Cacti. Traffic starts to grow as the evenings draws closer and everybody starts to ‘log-on’, so I decide to have a look at cacti to find the graphs for the ProCurve 2824 stop plotting any traffic at all after a magic 80Mbps… No bunny-hopping, so clearly not a counter rolling over (and well - 64bit counters anyway, go figure?).

Various calls to HP yield nothing. “The ProCurve 2824 supports 64-bit counters sir. You should plot graphs above 100Mbps easily”. Despite me trying to explain its not a counter issue - as its just not presenting data after 80Mbit precisely.

So I decide we’re using an old version of Cacti, i’ll install a new version onto a new server on the off chance (you do apparently stupid things when your desperate for a solution). If you think about it, we happily poll 64-bit from the Dells… what on earth could a new cacti do to help?

… well, it fixed it. I’ve no idea how, what was wrong or why. If anybody out there in the land of the internet has a clue as to why an old version of Cacti wouldn’t plot above 80Mbit from a ProCurve 2824 but would a PowerConnect 5324, i’d be delighted to hear it.

For anybody intrested.. here are examples of a 32-bit counter rolling over and a 64-bit counter being v.wierd at 80Mbit.





/end waffle

This entry was posted on Wednesday, January 9th, 2008 at 4:23 am and is filed under General. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.