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14-8 Riverstone Networks RS Switch Router User Guide Release 8.0
Creating Virtual Links OSPF Configuration Guide
14.7.1 Setting the Interface State
OSPF interfaces that are added to an area are enabled by default. You can disable them by using the
state disable
option with the
ospf set interface
command.
14.7.2 Setting the Default Cost of an OSPF Interface
The RS calculates the default cost of an OSPF interface using the reference bandwidth and the interface bandwidth.
The default reference bandwidth is 1000. It can be changed by using the
ospf set ref-bwdth
command.
A VLAN that is attached to an interface could have several ports of differing speeds. The bandwidth of an interface is
represented by the highest bandwidth port that is part of the associated VLAN. The cost of an OSPF interface is
inversely proportional to this bandwidth. The cost is calculated using the following formula:
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The following is a table of the port types and the OSPF default cost associated with each type:
14.8 CREATING VIRTUAL LINKS
In OSPF, virtual links can be established:
•
To connect an area via a transit area to the backbone
•
To create a redundant backbone connection via another area
Each ABR must be configured with the same virtual link. Note that virtual links cannot be configured through a stub
area.
Table 14-1 OSPF default cost per port type
Port Media Type Speed OSPF Default Cost
Ethernet 1000 1000 Mbps 2
Ethernet 10/100 100 Mbps 20
Ethernet 10/100 10 Mbps 200
WAN (T1) 1.5 Mbps 1333
WAN (T3) 45 Mbps 44