08 - Optimising OSPF Flashcards
A ___ cost is better. The cost is proportional to the B/W on the interface.
small
Cost = ___ /____ (in bits per second)
reference BW / interface BW
Why do problems occur with links faster than 100mb?
Because the OSPF cost has to be an integer, all links faster than FastEthernet will have a cost of 1. This can be fixed by changing the default reference bandwidth
How do you create default passive interfaces?
passive-interface default
How do you turn off a passive interface on specific interface?
no passive-interface
How do you view passive interfaces?
show ip protocols
How do you inject the default route into OSPF?
default-information originate
The process of advertising a contiguous set of addresses as a single address with shorter subnet mask. Reduces the number of routes a router must maintain.
Route summarisation or route aggregation
How do you view the OSPF database?
show ip ospf database
How do you create a prefix list?
ip prefix-list FROM_R2 deny 192.168.2.0/24
ip prefix-list FROM_R2 permit 0.0.0.0/0 le 32
How do you apply a prefix list to OSPF?
router ospf 1
area 1 filter-list prefix FROM_R2 out
How do you clear OSPF processes?
clear ip ospf process
For OSPF, the ____ command filters what ends up in the routing table, and only on the router on which the __ command is configured. It does not remove routes from the link-state database or area routers.
distribute-list in
One major difference between route maps and access lists is that route maps can use the __ commands to modify the packets or route.
set
Route map configuration generally consists of three parts:
- define the route map - Route-map MyRouteMap permit 10
- define match action - Match ip address prefix-list MyList
- define set action - Set metric-type type-1
