CCNA 3 Chapter 8 v5.1 + v6.0 Test Online 2018-2019

Hint

OSPF uses the formula: Cost = 100,000,000 / bandwidth. Because OSPF will only use integers as cost, any bandwidth of 100 Mb/s or greater will all equal a cost of 1.

Hint

The show ipv6 ospf neighbor command will verify neighbor adjacencies for OSPFv3 routers. The other options do not provide neighbor information.

Hint

Each OSPF router views the network differently as the root of a unique SPF tree. Each router builds adjacencies based on its own position in the topology. Each routing table in the area is developed individually through the application of the SPF algorithm. The link-state database for an area, however, must reflect the same information for all routers.

Hint

Link-state update (LSU) packets contain different types of link-state advertisements (LSAs). The LSUs are used to reply to link-state requests (LSRs) and to announce new information.

Hint

OSPFv6 messages can be sent to either the OSPF router multicast FF02::5, the OSPF DR/BDR multicast FF02::6, or the link-local address.

Hint

The OSPF metric is cost. The lowest cost path to a remote destination is the preferred path and is installed in the routing table.

Hint

OSPF router ID does not contribute to SPF algorithm calculations, nor does it facilitate the transition of the OSPF neighbor state to Full. Although the router ID is contained within OSPF messages when router adjacencies are being established, it has no bearing on the actual convergence process.

Hint

The basic command to implement OSPFv3 on a router uses the same process-id parameter as OSPFv2 to assign a locally-significant number to the OSPF process. OSPF does not use autonomous system numbers. Following the assignment of the process ID, a prompt will direct the user to manually assign a router ID. After the router ID is assigned, the reference bandwidth can be set.

Hint

During the exchange of hello packets, OSPF routers negotiate the election process and set the OSPF parameters. DBD packets are exchanged after that step has been completed. DBD packets contain abbreviated lists of link-state information. After that information has been exchanged, OSPF routers exchange Type 3 LSR packets to request further information.

Hint

There may be several reasons why two routers running OSPF will fail to form an OSPF adjacency, including these: The subnet masks do not match, causing the routers to be on separate networks. OSPF Hello or Dead Timers do not match. OSPF network types do not match. There is a missing or incorrect OSPF network command. Mismatched IOS versions, the use of private IP addresses, and different types of interface ports used on a switch are not causes for an OSPF adjacency failing to form between two routers.

Hint

Since serial interfaces do not have MAC addresses, OSPFv3 automatically assigns a link-local address to them derived from the first available MAC address from the pool of Ethernet interface addresses on the router. A FE80::/10 prefix is added. The router then applies the EUI-64 process to the MAC address by inserting FFFE into the middle of the existing 48-bit address and flipping the seventh bit.

Hint

The command to enable an OSPFv3 process on a router interface is ipv6 ospf process-id area area-id. In the case the process ID is 20 and the area ID is 0.

Hint

There is no need to have a DR/BDR election on a point-to-point link.

Hint

The show ipv6 route ospf command gives specific information that is related to OSPFv3 routes in the routing table. The show ipv6 route command will show the entire routing table. The show ip route and show ip route ospf commands are used with OSPFv2.

Hint

The show ip ospf neighbor command is used to verify that the router has formed an adjacency with its neighboring routers. The show ip ospf command displays the OSPF process ID and router ID, the OSPF area information, as well as the last time the SPF algorithm was calculated. The show ip ospf interface command provides detailed information about every OSPF-enabled interface.

Hint

The OSPFv3 router ID is configured in the IPv6 router configuration mode. The clear ipv6 ospf process privileged EXEC command forces OSPF on the router to renegotiate neighbor adjacencies. The interface serial 0/0/1 command causes the router to enter interface configuration mode where OSPFv3 is enabled by issuing the ipv6 ospf process-id area area-id command.

Hint

The first preference for an OSPF router ID is an explicitly configured 32-bit address. This address is not included in the routing table and is not defined by the network command. If a router ID that is configured through the router-id command is not available, OSPF routers next use the highest IP address available on a loopback interface, as loopbacks used as router IDs are also not routable addresses. Lacking either of these alternatives, an OSPF router will use the highest IP address from its active physical interfaces.

Hint

The active and passive states are used by EIGRP.

Hint

OSPF uses cost as a metric. OSPF calculates cost inversely to the bandwidth of an interface. The higher the interface bandwidth, the lower the cost of the interface.

Hint

OSPF designated routers are elected on multiaccess networks to disseminate LSAs to other OSPF routers. By having a single router disseminate LSAs, the exchanging of LSAs is more efficient.