This is an old story, perhaps a year ago, when I was working at one of telecommunication vendor. And I thank God, I got a lot of lessons and experiences while working there.
One day, my friend from NOC told me that the network couldn’t monitored from Cacti last night, but there was no traffic down. He asked me to check what happened.
Well, I was thinking that it was NMS problem. I started to check the alarm log on IPRAN core device.
An alarm 400136 ID 180933 level 5 occurred at 04:40:23 04-26-2016, cleared at 05
:54:05 04-26-2016 sent by xxx_9K8E_xxx_1461 PFU-0/1/0
%PORT% Physical interface status The physical interface xlgei-0/1/1/1 turned in
From the log I got notice that port xlgei-0/1/1/1 was down before, I found that this port is main link to IPBB PE router. So definitely the traffic passed through the backup link.
But wait, why no traffic shown by Cacti server?