What command sequence will configure a router to run OSPF and add network 10.1.1.0 /24 to
area 0?
A.
router ospf area 0
network 10.1.1.0 255.255.255.0 area 0
B.
router ospf
network 10.1.1.0 0.0.0.255
C.
router ospf 1
network 10.1.1.0 0.0.0.255 area 0
D.
router ospf area 0
network 10.1.1.0 0.0.0.255 area 0
E.
router ospf
network 10.1.1.0 255.255.255.0 area 0
F.
router ospf 1
network 10.1.1.0 0.0.0.255
OSPF is an interior gateway routing protocol that uses link states rather than distance vectors for path selection. OSPF propagates link-state advertisements rather than routing table updates. Because only LSAs are exchanged instead of the entire routing tables, OSPF networks converge more quickly than RIP networks.
OSPF uses a link-state algorithm to build and calculate the shortest path to all known destinations. Each router in an OSPF area contains an identical link-state database, which is a list of each of the router usable interfaces and reachable neighbors.
The advantages of OSPF over RIP include the following:
•OSPF link-state database updates are sent less frequently than RIP updates, and the link-state database is updated instantly rather than gradually as stale information is timed out.
•Routing decisions are based on cost, which is an indication of the overhead required to send packets across a certain interface. The ASA calculates the cost of an interface based on link bandwidth rather than the number of hops to the destination. The cost can be configured to specify preferred paths.
The disadvantage of shortest path first algorithms is that they require a lot of CPU cycles and memory.
The ASA can run two processes of OSPF protocol simultaneously, on different sets of interfaces. You might want to run two processes if you have interfaces that use the same IP addresses (NAT allows these interfaces to coexist, but OSPF does not allow overlapping addresses). Or you might want to run one process on the inside, and another on the outside, and redistribute a subset of routes between the two processes. Similarly, you might need to segregate private addresses from public addresses.
You can redistribute routes into an OSPF routing process from another OSPF routing process, a RIP routing process, or from static and connected routes configured on OSPF-enabled interfaces.
The ASA supports the following OSPF features:
•Support of intra-area, interarea, and external (Type I and Type II) routes.
•Support of a virtual link.
•OSPF LSA flooding.
•Authentication to OSPF packets (both password and MD5 authentication).
•Support for configuring the ASA as a designated router or a designated backup router. The ASA also can be set up as an ABR.
•Support for stub areas and not-so-stubby-areas.
router ospf process_id
Example:
hostname(config)# router ospf 1
======================================
This step defines the IP addresses on which OSPF runs and to define the area ID for that interface (see below)
network ip_address mask area area_id
Example:
hostname(config)# router ospf 2
hostname(config-router)# network 10.0.0.0
255.0.0.0 area 0
OSPF network command uses wildcard mask:
0.0.0.255 area 0