FTOS Configuration Guide for the C-Series - Force10 Networks

Cost is a numbered rating 1-65535. The higher the number, the greater the cost. The cost assigned reflects
the cost should the router fail. When a router fails and the cost is assessed, a new priority number results.
Figure 377 Priority and Costs Example
Router 1
Priority 200
Cost 21
Router 2
Priority 180
Cost 50
Implementing OSPF with FTOS
The Force 10 Operating System (FTOS) supports 1 OSPF process ID per system. FTOS supports up to
10,000 OSPF routes. Within that 10,000 up to 8,000 routes can be designated as external and up to 2,000
designated as inter/intra area routes.
• Grace (to support Hitless OSPF Restart)
Router 3
Priority 100
Cost 25
Router 4
Priority 150
Cost 20
Router 1 selected by the system as DR.
Router 2 selected by the system as BDR.
If R1 fails, the system "subtracts" 21 from R1's priority
number. R1's new priority is 179.
R2 as both the selected BDR and the now-highest
priority, becomes the DR.
If R3 fails, the system "subtracts" 50 from its priority.
R2's new priority is 130.
R4 is now the highest priority and becomes the DR.
FTOS supports Stub areas, Totally Stub (No Summary) and Not So Stubby Areas (NSSAs) and supports
the following LSAs, as discussed earlier in this document.
• Router (type 1)
• Network (type 2)
• Network Summary (type 3)
• AS Boundary (type 4)
536 Open Shortest Path First