Brocade FastIron Ethernet Switch Layer 3 Routing Configuration Guide - Manual (Page 281)

Limitations
• If a neighbor router is inactive for 30 seconds, and if the standby module takes over in another 10
seconds, the neighbor router cannot be dropped. The inactivity timer starts again and takes another
40 seconds to drop the neighbor router.
• In standby module, the valid neighbor states are LOADING, DOWN, 2WAY, and FULL. If the active
management processor (MP) fails when the neighbor state is LOADING, the standby module cannot
continue from LOADING, but the standby can continue from 2WAY and tries to establish adjacency
between the neighboring routers.
• The minimum OSPF dead-interval timer value is 40 seconds (default dead-interval value). When the
dead-interval value is configured less than this minimum value, OSPF NSR cannot be supported.
Interface synchronization
Interface information is synchronized for interfaces such as PTPT, broadcast, and non-broadcast.
Interface wait time is not synchronized to the standby module. If an interface waits for 30 seconds to
determine the identity of designated router (DR) or backup designated router (BDR), and if the standby
module takes over, the wait timer starts again and takes another 40 seconds for the interface state to
change from waiting to BDR, DR, or DROther.
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.
Limitations
FastIron Ethernet Switch Layer 3 Routing Configuration Guide 281
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