Important Considerations - 3Com corebuilder 3500 Implementation Manual

OSPF Interfaces 385
Consider the following guidelines when you configure router interfaces:
Important
Considerations
To set the OSPF interface mode to active, enable IP routing.
Because designated routers and backup designated routers have the
Designated routers
most OSPF work to do within an area, select routers that are not
already loaded with CPU-intensive activities to be the designated
router and backup designated router.
Because router priority is assigned on a per-interface basis, a single
router with interfaces within several different areas can serve as
designated router for those areas. But because a designated router
has several CPU-intensive responsibilities, it is not a good idea to select
the same router as designated router for many areas simultaneously.
Routers that have an interface priority of 0 cannot serve as a
designated router or backup designated router.
On a broadcast network, if there is no designated router or backup
designated router (such as when all routers have a priority of 0),
routers do not form neighbor adjacencies, and routing information is
not exchanged.
Set the area ID to the same value for all routers on the network
Area ID
segment. All routers in the same area must have the same area ID.
The backbone area 0.0.0.0 is configured by default. The system
associates all newly defined OSPF interfaces with the backbone area.
You can change this association by changing the area ID for the
selected interface.
The default value for the transmit delay is 1 second.
Transmit delay
Set the transmit delay to an integer value greater than 0.
To set the transmit delay, take into account the transmission and
propagation delays for the interface.
Set the transmit delay according to the link speed; use a longer
transmit delay for slower link speeds.
The transmit delay is more effective on very low link speeds.
The default value for the Hello interval is 10 seconds.
Hello interval
The smaller the Hello interval, the faster that topological changes are
detected, although more routing traffic ensues.
Set the Hello interval to the same value for all routers on the same
network segment.