Brocade Multi-Service IronWare Routing Configuration Guide (Supporting R05.6.00) - Manual (Page 223)

Multi-Service IronWare Routing Configuration Guide 195
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BFD with OSPF NSR
BFD with OSPF NSR
Bidirectional forwarding detection (BFD) supports MP switchover and all BFD sessions for OSPF
with graceful OSPF NSR, which are in the up state after the switchover. The BFD sessions for OSPF
that do not use OSPF NSR are cleared before the switchover and then re-established on the new
active MP after the MP switchover.
In case the active MP learns an OSPF neighbor and then restarts before a new BFD session is
established, the standby module will not have a BFD session for the new OSPF neighbor. To
overcome this and to support OSPF NSR with BFD, the following functions are supported when the
active MP restarts:
• During MP switchover, BFD checks whether OSPF NSR is enabled. If OSPF NSR is enabled, the
existing BFD sessions for OSPF is maintained during the switchover.
• OSPF sets up or clears the BFD sessions after OSPF neighbor transition.
• After the switchover, BFD sessions correspond with the active OSPF neighbor.
Standby module operations
The standby management module with OSPF configuration performs the following functions.
Neighbor database
Neighbor information is updated in the standby module based on updates from the active module.
Certain neighbor state and interface transitions are synchronized to the standby module. By
default, the neighbor timers on the standby module are disabled.
LSA database
The standby module processes LSA synchronization events from the active module and unpacks
the LSA synchronization information to directly install it in its LSDB as the LSA has already been
processed on the active module. The information required to install all types of LSAs (and special
LSAs such as Grace LSAs) is packed by OSPF on the active module in the synchronization buffer, so
that you can directly install LSAs on the standby module without extra processing.
The standby module is not allowed to originate any LSAs of its own. This is to maintain all
information consistently from the active module. The active module synchronizes self-originated
LSAs to the standby module.
LSA aging is not applicable on the standby module. During synchronization from the active, the
current LSA age is recorded and the new database timestamp is created on the standby to later
derive the LSA age as needed.
When the active module sends the LSAs to the standby module, based on the message, the
standby module deletes or updates its link state database with the latest information.
LSA acknowledging or flooding are not done on the standby module. When the LSA synchronization
update arrives from the active module, it will be directly installed into the LSDB.