3Com Switch 7750 Configuration Guide Guide

OSPF Network Adjustment and Optimization 303
n
■ Default Hello and Dead timer values will be restored once the network type is
changed.
■ Do not set an LSA retransmission interval that is too short. Otherwise,
unnecessary retransmission will occur. LSA retransmission interval must be
greater than the round trip time of a packet between two routers.
Configuring the LSA
transmission delay
n
The transmission of OSPF packets on a link also takes time. Therefore, a
transmission delay should be added to the aging time of LSAs before the LSAs are
transmitted. For a low-speed link, pay close attention on this configuration.
Configuring the SPF
Calculation Interval
Whenever the LSDB of OSPF is changed, the shortest paths need to be
recalculated. When the network changes frequently, calculating the shortest paths
immediately after LSDB changes will consume enormous resources and affect the
operation efficiency of the router. By adjusting the minimum SPF calculation
Set the hello interval on the
interface
ospf timer hello seconds
Optional
By default, p2p and
broadcast interfaces send
Hello packets every 10
seconds; while p2mp and
NBMA interfaces send Hello
packets every 30 seconds.
Set the poll interval on the
NBMA interface
ospf timer poll seconds
Optional
By default, poll packets are
sent every 120 seconds.
Set the dead time of the
neighboring router on the
interface
ospf timer dead seconds
Optional
By default, the dead time for
the OSPF neighboring router
on a p2p or broadcast
interface is 40 seconds and
that for the OSPF neighboring
router on a p2mp or NBMA
interface is 120 seconds.
Set the interval at which the
router retransmits an LSA to
the neighboring router on the
interface
ospf timer retransmit
interval
Optional
By default, this interval is five
seconds.
Table 225 Configure OSPF timers
Operation Command Description
Table 226 Configure the LSA transmission delay
Operation Command Description
Enter system view system-view -
Enter interface view
interface interface-type
interface-number
-
Configure the LSA
transmission delay
ospf trans-delay seconds
Optional
By default, the LSA
transmission delay is one
second.