OSPF Routing Configuration Flashcards

A network administrator configures an ArubaOS-CX switch for OSPF. The administrator wants to advertise the network associated with interface 1/1/5 into OSPF, but prevent the switch from forming OSPF adjacencies on that interface. Which command sequence achieves this goal?

Answer: switch(config)# interface 1/1/5 switch(config-if)# ip ospf passive

On ArubaOS-CX switches, the `ip ospf passive` command, configured under a specific interface, is the correct method to prevent OSPF Hello packets from being sent on that interface while still allowing the interface's network to be advertised. The `passive-interface ` command is not a valid syntax in the router OSPF context on ArubaOS-CX. `passive-interface default` would make all interfaces passive, and `ip ospf shutdown` would disable OSPF entirely on the interface.

An ArubaOS-CX switch needs to be configured to participate in OSPF Area 0. Which of the following is the minimum required configuration to establish an OSPF process and assign an interface to Area 0?

Answer: switch(config)# router ospf 1 switch(config-ospf-1)# router-id 10.1.1.1 switch(config-ospf-1)# area 0 switch(config)# interface 1/1/1 switch(config-if)# ip ospf 1 area 0

To configure OSPF on an ArubaOS-CX switch, you must first create the OSPF process using `router ospf `. A `router-id` must be configured for the process to start. Then, you must explicitly enable OSPF on an interface and assign it to an area using the `ip ospf area ` command under the interface configuration context.

A network engineer is configuring OSPF on an ArubaOS-CX switch and wants to ensure the router ID is statically set to 10.0.0.1. If the switch has a loopback interface with IP address 172.16.0.1 and a physical interface with IP address 192.168.1.1, which command correctly sets the OSPF router ID?

Answer: switch(config)# router ospf 1 switch(config-ospf-1)# router-id 10.0.0.1

The OSPF router ID on an ArubaOS-CX switch is configured within the OSPF process context. The correct command is `router-id ` entered after the `router ospf ` command. If not statically configured, the router ID is automatically selected, typically using the highest IP address of a loopback interface.

In an OSPF network running on ArubaOS-CX switches, what is the primary purpose of configuring MD5 authentication on an interface?

Answer: To ensure that routing updates are only accepted from trusted, authorized neighbor routers.

OSPF authentication, whether simple-text or MD5, is designed to enhance security by ensuring that a router only forms adjacencies and accepts routing updates from other routers that share the same pre-configured key. This prevents unauthorized routers from injecting false routing information. MD5 provides cryptographic authentication but does not encrypt the content of the Link-State Updates (LSUs).

A network administrator is configuring a multi-area OSPF network on ArubaOS-CX switches. An interface on a switch connects to Area 0.0.0.0. What is the common name for this area?

Answer: The Backbone Area

In OSPF, Area 0 (or 0.0.0.0) has a special designation as the backbone area. All other areas in a multi-area OSPF design must connect to the backbone area, either directly or through a virtual link, to ensure that routing information can be exchanged between non-backbone areas.

Which of the following commands would an administrator use on an ArubaOS-CX switch to change the OSPF network type on an interface to support a direct, two-router link efficiently?

Answer: switch(config-if)# ip ospf network point-to-point

For a link that connects only two routers, the `point-to-point` network type is the most efficient. It eliminates the need for Designated Router (DR) and Backup Designated Router (BDR) elections, which are unnecessary in a two-router topology, leading to faster convergence. The command to set this is `ip ospf network point-to-point` under the interface configuration.