Implementing Cisco Service Provider Advanced Routing Solutions

B.

Segment Routing (SR) is a technology that simplifies the deployment and operation of network services by allowing network administrators to steer traffic along any path in the network using segment identifiers. In the context of Interior Gateway Protocols (IGPs), such as OSPF and IS-IS, segment routing enables a more flexible and scalable way of distributing routing information and traffic engineering.

To enable segment routing for IGPs, you must configure it on the routers that run the IGP. There are two possible ways to enable segment routing for IGPs: globally or under the routing process.

• Global Configuration: When segment routing is enabled globally, all routing processes on the router can use SR. To enable segment routing globally, you can use the following command:

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Router(config)# segment-routing global 

• Per-Process Configuration: When segment routing is enabled under a routing process, only that process can use SR. To enable segment routing under an IGP process, you can use the following command:

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Router(config-router)# segment-routing 

Now, coming to the given options:

Option A: "Segment routing must first be enabled under then routing process and then globally." This statement is incorrect because you can enable SR either globally or under the routing process, and the order does not matter.

Option B: "Segment routing must first be enabled globally and then under the routing process." This statement is partially correct because you can enable SR globally first and then under the routing process, but you can also enable it only under the routing process.

Option C: "Segment routing can be enabled only under the routing process." This statement is incorrect because you can enable SR either globally or under the routing process.

Option D: "Segment routing can be enabled only globally." This statement is incorrect because you can enable SR either globally or under the routing process.

Therefore, the correct answer is option B: "Segment routing must first be enabled globally and then under the routing process." However, it is important to note that you can also enable SR only under the routing process, which makes this option partially correct.