Routenberechnung - Hirschmann MACH 4000 User Manual

OSPF

7.5 Routenberechnung

After the LSDs are learned and the neighbor relationships go to the full state,
every router calculates a path to every destination using the Shortest Path
First (SPF) algorithm. After the optimal path to every destination has been
determined, these routes are entered in the routing table. The route
calculation is generally based on the accessibility of a hop and the metric
(costs). The costs are added up over all the hops to the destination.
The costs of an individual router interface are based on the available
bandwidth of this link. The calculation for the standard setting is based on the
following formula:
Metric = 10 000 000 / bandwidth (bits/sec) .
For Ethernet, this leads to the following costs:
10 Mbit 10
100 Mbit 1
1000 Mbit 1 (0.1 rounded up to 1)
The table shows that this form of calculation in the standard configuration
does not permit any distinction between fast Ethernet and gigabit Ethernet.
You can change the standard configuration by assigning a different value for
the costs to each OSPF interface. This enables you to differentiate between
fast Ethernet and gigabit Ethernet.
enable
configure
interface 1/1
ip ospf cost 2
Routing L3P
Release 4.0 11/07
7.5 Routenberechnung
Switch to the Priviledged EXEC mode.
Switch to the Configuration mode.
Switch to the Interface Configuration mode of
interface 1/1.
Assigns to port 1.1 the value 2 for the OSPF
costs.
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