reboot spikes strike again

Hello,

I've recenly upgraded my FreeBSD router. New MRTG is 2.17.4, which I
use to self-monitor traffic on local ethernet interfaces.

>From the very start I can observe traffic spikes after each reboot.
I thought the days of MRTG spikes were gone for long...

As I could read, MRTG reads system uptime to check for reboot when
counter overflow is detected. This seems to be done (uptime 40
secs), according to debug log: 

2013-10-31 16:08:02 -- --snpo: run snmpget from ifHCInOctets&ifHCOutOctets:xxxxxxxx@localhost
2013-10-31 16:08:02 -- --snpo: (0) Confcache Match rl1 -> .3
2013-10-31 16:08:02 -- --snpo: (1) Confcache Match rl1 -> .3
2013-10-31 16:08:02 -- --snpo: SNMPGet from xxxxxxxx@localhost:::::2 -- ifDescr.3,ifHCInOctets.3,ifDescr.3,ifHCOutOctets.
3,sysUptime,sysName
2013-10-31 16:08:02 -- --snpo: SNMPfound -- 'rl1', '130249', 'rl1', '32200', '0:00:40', 'xxxxxx.xxxxxx.net'
2013-10-31 16:08:02 -- --snpo: (0) Descr crosscheck OK
2013-10-31 16:08:02 -- --snpo: (1) Descr crosscheck OK


The mrtg config section is nothing extraordinary:

Options[_]: growright, bits, unknaszero

Title[traffic-ciapek-rl1]: rl1
Target[traffic-ciapek-rl1]: \rl1:xxxxxxxx@localhost:::::2
MaxBytes[traffic-ciapek-rl1]: 12500000
Options[traffic-ciapek-rl1]: growright, bits, unknaszero


I've also checked two different SNMP daemons, without any
improvement. Any ideas, what can be the spiky reason?


-- 
Wojtuś