OSPF Configuration Flashcards
OSPFv2 is enabled using __ command?
OSPFv2 is enabled using the:
router ospf process-id
global configuration mode command.
The process-id value represents a number between 1 and 65,535 and is selected by the network administrator.
how does the router determine the router ID? (1 of 3 criteria)
- The router ID is explicitly configured using the: OSPF router-id “rid”
router configuration mode command. The rid value is any 32-bit value expressed as an IPv4 address. This is the recommended method to assign a router ID. - If the router ID is not explicitly configured, the router chooses the highest IPv4 address of any of configured loopback interfaces. This is the next best alternative to assigning a router ID.
- If no loopback interfaces are configured, then the router chooses the highest active IPv4 address of any of its physical interfaces.
OSPF: How do you configure a loopback interface on the Router?
R1(config-if)# interface Loopback 1
OSPF: How do you manually assign a router ID?
Use the router-id rid router configuration mode command to manually assign a router ID. Then use the show ip protocols command to verify the router ID.
R1(config)# router ospf 10
R1(config-router)# router-id 1.1.1.1
R1# show ip protocols | include Router ID
After a router selects a router ID, an active OSPF router does not allow the router ID to be changed until the router is reloaded or the OSPF process is reset. How do you then reset the adjacencies to Modify a Router ID?
Use the “clear ip ospf process” command to reset the adjacencies.
One type of network classified by OSPF is a point-to-point network. What command(s) can specify the interfaces that belong to a point-to-point network?
You can specify the interfaces that belong to a point-to-point network by configuring the “network” command.
Router(config-router)# network “network-address” “wildcard-mask” area “area-id”
(You can also configure OSPF directly on the interface with the ip ospf command)
What command do you use to configure OSPF directly on the interface?
To configure OSPF directly on the interface, use the “ip ospf interface” configuration mode command.
Router(config-if)# ip ospf “process-id” area “area-id”
remove the network commands by using the ____ form of the network commands
“no”
ex:
R1(config-router)# no network 10.10.1.1 0.0.0.0 area 0
By default, OSPF messages are forwarded out all OSPF-enabled interfaces. However, these messages really only need to be sent out interfaces that are connecting to other OSPF-enabled routers. What are 3 reasons we would want to create a Passive Interface?
Inefficient Use of Bandwidth - Available bandwidth is consumed transporting unnecessary messages.
Inefficient Use of Resources - All devices on the LAN must process and eventually discard the message.
Increased Security Risk - Without additional OSPF security configurations, OSPF messages can be intercepted with packet sniffing software. Routing updates can be modified and sent back to the router, corrupting the routing table with false metrics that misdirect traffic.
What command is used to Configure Passive Interfaces
“passive-interface” router configuration mode command
ex:
R1(config-router)# passive-interface loopback 0
On what type of network does OSPF elects a DR and BDR?
multiaccess networks
What are all other routers besides the DR and BDR called?
All other routers become a DROTHER (a router that is neither the DR nor the BDR).
What is the multiaccess address that DROTHERS use?
DROTHERs use the multiaccess address 224.0.0.6 (all designated routers)
What is the multiaccess address that the DR uses?
The DR uses the multicast IPv4 address 224.0.0.5 which is meant for all OSPF routers.
What command is used to verify the OSPFv2 adjacencies?
To verify the OSPFv2 adjacencies, use the show ip ospf neighbor command
R1# show ip ospf neighbor
