Questions and Answers
DROTHERs use the multiaccess address 224.0.0.______ to send OSPF packets to the DR and BDR.
6
In the multiaccess topology, there are three routers interconnected over a common Ethernet multiaccess network, ______.
192.168.1.0/24
OSPF has automatically elected a ______ and BDR in multiaccess networks.
DR
R3 has been elected as the DR because its router ID is ______.
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R2 is the BDR because it has the second highest router ID, which is ______.
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To verify OSPF router roles, use the ______ command.
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R1 is not the DR or BDR, but is a DROTHER with a default priority of ______.
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R1 has two adjacencies: one with the ______ and one with the DR.
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To verify the OSPFv2 adjacencies, use the show ip ospf ______ command.
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The state of neighbors in multiaccess networks can be ______ such as FULL or DROTHER.
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FULL/DROTHER indicates a DR or BDR router that is fully ______ with a non-DR or BDR router.
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A router in the FULL/DR state is fully adjacent with the indicated ______ neighbor.
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The normal state for an OSPF router is usually ______.
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In a 2-WAY state, a non-DR or BDR router can exchange ______ packets with another non-DR or BDR router.
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If a router is stuck in a state other than FULL, it is an indication that there are ______ in forming adjacencies.
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The Backup Designated Router (BDR) can also be referred to by the ______ neighbor.
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The ______ state is considered normal in a multiaccess broadcast network.
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In OSPF, the Internet Address for a router can be expressed as ______/24.
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The command 'show ip interface brief' is used to verify that the desired interfaces are active with correct ______.
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After configuring single-area OSPFv2, it is important to verify the ______.
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The command 'show ip route' is particularly useful for verifying that the routing ______ contains all the expected routes.
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To verify that OSPF is operating as expected, additional commands include 'show ip ospf ______'.
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The command 'show ip ospf protocols' provides information about the OSPF ______.
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If a router's neighboring router is not displayed, the two routers have not formed an OSPFv2 ______.
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The states of neighboring routers can be verified using the 'show ip ospf neighbor' command, where a router must be in the state of ______.
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To confirm communication between routers, you must check the ______ relationships formed by OSPF.
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In OSPFv2, the command 'show ip ospf interface' shows the status of OSPF's ______.
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The process of verifying OSPF configurations is essential to ensure proper ______ in the network.
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To verify the OSPFv2 interface intervals, use the show ip ospf ______ command.
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The router located between an OSPF routing domain and a non-OSPF network is called the ______.
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To propagate a default route, the ASBR must be configured with a default static route using the ip route 0.0.0.0 0.0.0.0 ______ command.
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Additional commands for determining that OSPF is operating as expected include: show ip ospf ______.
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To modify the OSPFv2 Hello and Dead intervals manually, use the commands ip ospf hello-interval and ip ospf ______.
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To configure OSPF directly on the interface, use the ip ospf ______ configuration mode command.
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The DR uses the multicast IPv4 address ______ which is meant for all OSPF routers.
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Only the DR and BDR listen for ______.
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To verify the roles of the OSPFv2 router, use the ______ command.
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To verify the OSPFv2 ______, use the show ip ospf neighbor command.
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The OSPF DR and BDR election decision is based on the router with the highest interface ______ as the DR.
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The router with the second highest interface priority is elected as the ______.
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If the interface priorities are equal, then the router with the highest ______ is elected the DR.
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The state of neighbors in multiaccess networks can be: FULL/DROTHER, FULL/______, FULL/BDR, or 2-WAY/DROTHER.
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To stop transmitting routing messages through a router interface, use the ______ router configuration mode command.
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Study Notes
OSPF Multiaccess Networks
- The multicast address 224.0.0.6 is used by DROTHERs to send OSPF packets to the Designated Router (DR) and Backup Designated Router (BDR).
- Only DR and BDR routers listen for traffic on the address 224.0.0.6.
- In a common Ethernet multiaccess network (192.168.1.0/24), OSPF automatically elects a DR and a BDR based on router IDs.
DR and BDR Election
- Router R3 is elected as the DR with the highest router ID (3.3.3.3).
- Router R2 is the BDR, having the second highest router ID (2.2.2.2).
- To check the OSPF roles, the command
show ip ospf interfacedisplays the status of the routers.
Verifying OSPF Roles
- R1, identified as a DROTHER, has a default priority of 1 and does not participate as a DR or BDR.
- Adjacencies between routers are confirmed through output details, listing neighbor router IDs and their roles.
OSPF Neighbor States
- OSPFv2 neighbor states in multiaccess networks include:
- FULL/DROTHER: Fully adjacent with a DROTHER; can exchange OSPF data.
- FULL/DR: Fully adjacent with the DR.
- FULL/BDR: Fully adjacent with the BDR.
- 2-WAY/DROTHER: Normal state for non-DR/BDR routers, indicates a Hello packet relationship.
Default Route Propagation
- Default routes can be propagated in OSPF to ensure connectivity through the ASBR (Autonomous System Boundary Router).
- Configuration requires establishing a default static route and utilizing the command
default-information originate.
OSPF Verification Commands
- To verify routing configurations, use:
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show ip interface briefto check active interfaces. -
show ip routeto confirm routing table entries. - Additional commands:
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show ip ospf neighborfor neighbor adjacency. -
show ip ospffor general OSPF status. -
show ip ospf interfacefor interface-specific details.
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OSPF Configuration Commands
- Key commands for OSPF configuration include:
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router ospf process-idto enable OSPF. -
network network-address wildcard-mask area area-idfor area assignment. - Interface-specific commands like
ip ospf hello-intervalandip ospf dead-intervalto adjust timing.
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Additional OSPF Concepts
- OSPF uses a designated router to collect and distribute Link-State Advertisements (LSAs).
- If the DR fails, the BDR assumes the DR role and the remaining routers become DROTHERs.
- OSPF encourages efficient routing through the use of router priority and router IDs during the election process.
- The interface type can be set to point-to-point using
ip ospf network point-to-point, disabling the DR/BDR election in point-to-point topologies.
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Description
Test your understanding of the OSPF protocol in multiaccess networks. This quiz covers key concepts such as designated routers, multicast addresses, and OSPF packet transmission. Get ready to dive deep into network routing mechanisms!
