The Nortel Ethernet Routing Switch 8600 supports a feature called link flap detect. This feature is designed to detect a port whose link is flapping up and down and potentially disable the port and/or issue an SNMP trap. The feature allows the configuration of a specific frequency and interval which can be used to fine tune control of the feature.
A few years ago we deployed about 25 Voice Gateway Media Cards (VGMC) across five different Nortel Call Server 1000Ms. We almost immediately started to notice a problem between the VGMCs and the ERS 8600 switches. The VGMCs would link up and link down multiple times as they booted up. While there is technically no real problem with the VGMC you can run straight into a road block if you reboot the card multiple times in a short period of time. Without getting to crazy on the explanation the ERS 8600 switch would potentially disable the switch port(s) that connected to the VGMCs if they were rebooted to often during a 60 minute period. The problem was only observed while the VGMCs were booting up, once the VGMC was up and running the problem never occurred. I believe the link flap detect feature is enabled by default unless specifically disabled.
This may be an old problem that might have already been corrected by Nortel but I still have the link flap detect feature disabled on the Ethernet Routing Switch 8600s that connect to our Nortel Voice Gateway Media Cards.
ERS8600:5# config sys link-flap-detect interval 60 ERS8600:5# config sys link-flap-detect frequency 10 ERS8600:5# config sys link-flap-detect auto-port-down disable ERS8600:5# config sys link-flap-detect send-trap enable
The configuration can be confirmed using the following command;
ERS8600:5# show sys link-flap-detect general-info Auto Port Down: enable Send Trap : enable Interval : 60 Frequency : 10
The frequency defines how often a port can go down, where the default is 10 (times). The default interval is 60 minutes; therefore the port will be disabled if the port goes down 10 times within 60 minutes.