|  | 4.2 | PPP Session Establishment
| 4.2.4 | Phase 3: network-layer protocol configuration negotiation
When LCP finishes the link-quality determination phase, network-layer protocols can be separately configured by the appropriate NCP and can be brought up and taken down at any time. In this phase, the PPP devices send NCP packets to choose and configure one or more network-layer protocols (such as IP). When each of the chosen network-layer protocols has been configured, datagrams from each network-layer protocol can be sent over the link. If LCP closes the link, it informs the network-layer protocols so that they can take appropriate action. When PPP is configured, you can check its LCP and NCP states by using the show interfaces command.