# Guidelines for Configuring 802.3ah OAM Link-Fault Management

Keep the following points in mind when you configure OAM link-fault management on Ethernet interfaces:

- The OAM application transmits and receives an OAM PDU at a maximum frequency of every 100 milliseconds (10 OAM PDUs/sec) on every port on the set of IOAs for a line module. The most impact on performance might occur on ES2 4G LMs with two GE-8 I/O modules (16 ports) that cause 160 OAM PDUs to be transmitted per second. Also, the OAM application must query MAC-layer statistics (up to 6-8 for frame errors) every 10 seconds and errored symbol statistics per second.
- Because the outage time of the forwarding controller can last up to about 15 seconds or longer, the 802.3ah OAM feature does not support unified ISSU. The link-fault management of Ethernet interfaces is halted during a unified ISSU operation. Monitoring resumes immediately after the unified ISSU operation is completed.
- Although OAM configurations on an interface are preserved during a stateful SRP switchover procedure, the retention of such OAM settings depends on the time that the stateful SRP switchover process takes to complete. If the stateful SRP switchover operation causes a traffic disruption of more than two seconds, the previously configured OAM settings are affected. We recommend that you configure the number of PDUs that are failed to be received by an OAM entity before it generates a link fault/down event to be greater than two, and the high and low thresholds for an error to be exceeded on an Ethernet OAM interface to be more than two seconds.
- 802.3ah OAM functionality is not supported on SRP Ethernet interfaces. Also, JunosE Software does not support unidirectional operation of Ethernet OAM links, which enable the OAM entities to send Link Fault Information OAM PDUs to the peer whenever a receive path failure is detected. In addition, an active mode OAM entity can retrieve and respond to the performance variables that it receives from its peer entity. However, the local OAM entity does not send a list of such performance variables that it can process from the peer.

#### Related Documentation

- OAM Feature Overview
- Interrelationship of OAM Link-Fault Management with Ethernet Subsystems
- Configuring 802.3ah OAM Link-Fault Management