3Com SuperStack 4 Configuration Manual page 127

Setting an Interval for LSA Retransmission between Neighboring Routers
If a router transmits an LSA (Link State Advertisements) to the peer, it requires an
acknowledgement packet from the peer. If it does not receive the
acknowledgement packet within the retransmit time, it retransmits this LSA to the
neighbor. You can configure the value of the retransmission interval.
Perform the following configuration in Interface View
Table 142 Setting an Interval for LSA Retransmission between Neighboring Routers
Operation
Configure the interval of LSA retransmission for
the neighboring routers
Restore the default LSA retransmission interval
for the neighboring routers
By default, the interval for neighboring routers to retransmit LSAs is five seconds.
The value of
interval
be transmitted and returned between two routers.
An LSA retransmission interval that is too small will cause unecessary
retransmission.
Setting a Shortest Path First (SPF) Calculation Interval for OSPF
Whenever the OSPF LSDB changes, the shortest path requires recalculation.
Calculating the shortest path after the change consumes enormous resources and
affects the operating efficiency of the router. Adjusting the SPF calculation interval,
however, can restrain the resource consumption due to frequent network
changes.
Perform the following configuration in OSPF View.
Table 143 Setting the SPF calculation interval
Operation
Set the SPF calculation interval
Restore the SPF calculation interval
By default, the interval for SPF recalculation is 5 seconds.
Configuring STUB Area of OSPF
STUB areas are special LSA areas in which the ABRs do not propagate the learned
external routes of the AS. In these areas, the routing table sizes of routers and the
routing traffic are significantly reduced.
The STUB area is an optional configuration attribute, but not every area conforms
to the configuration condition. Generally, STUB areas, located at the AS
boundaries, are those non-backbone areas with only one ABR. Even if this area has
multiple ABRs, no virtual links are established between these ABRs.
To ensure that the routes to destinations outside the AS are still reachable, the ABR
in this area will generate a default route (0.0.0.0) and advertise it to the non-ABR
routers in the area.
Command
ospf timer retransmit
undo ospf timer retransmit
should be bigger than the interval in which a packet can
Command
spf-schedule-interval
undo spf-schedule-interval
OSPF Configuration 139
interval
seconds
seconds