User's Manual

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group of routers. Generally speaking, management distance is an integer between 0-255, the higher the value
is, the lower the reliability level it is. If the management distance is 255, then the route information source will
not be trusted and should be neglected.
OSPF uses 3 different types of management distances: inter-domain, inner-domain and exterior. The route
within an area is inner-domain; the route to other areas is inter-domain; the route distributed from other route
protocol domains is exterior. The default value of every kind of route is 110.
Under router configuration mode, use the following command to configure the distance value of OSPF:
Command Purpose
distance ospf
[
intra-area
dist1] [
inter-area
dist2] [
external
dist3]
Change the management distance value of
OSPF inner-domain, inter-domain and exterior
route.
60.3.13 Configuring the Route Calculation Timer
You can configure the time delay between the time when OSPF receives topologic change information and
when it starts to calculate SPF. You can also configure the interval between two consecutive calculations of
SPF. Under router configuration mode, use the following command to configure:
Command Purpose
timers delay
delaytime Set the time delay in the route calculation in a
area.
timers hold
holdtime
Set the minimum time interval of route
calculation in a area.
60.3.14 Configuring the On-Demand Link
OSPF over on-demand circuits is an upgrade of OSPF, which enables the protocol more efficient in case of
on-demand dialing network surfing. The OSPF protocol is to regularly exchange the HELLO packets and the
link-state broadcast-refresh packets among the connected routers after the connection is first established or
the information contained in the packet is changed, which means that the minimum spanning tree will be
recalculated and the packet will be transmitted only when the topology is really changed.
If the point-to-point connection is among the routers, the configuration should be conducted on one terminal.
Of cource, the router on the other terminal must support this trait. If the point-to-multipoint connection is among
the routers, the configuration must be conducted on the multipoint terminal.
It is recommended to configure the on-demand dialing in the STUB area. If this attribute is configured on each
router in the STUB area, the routers outside the STUB area are allowed not to support the on-demand dialing.
If on-demand dialinh is configured in a standard area, other standard areas must support this trait, because
the second kind of external link-state broadcast packets will be broadcast in all areas.
When the trait is configured on the broadcast-based network, the link-state broadcast packets can be restraint,
while the HELLO packets cannot be restraint. That’s because the HELLO packets are used to maintain the
neighborhood relation and to select DR.
Run the following command in interface mode:
Command Purpose