Dual-Device Hot Backup on the LAC Side

Context

The following requirements must be met to implement dual-device hot backup when a protection tunnel is set up between two LACs:
  • The master and backup LACs use the same IP address to establish L2TP tunnels with the LNS.
  • The master and backup LACs synchronize L2TP tunnel and user information with each other.
  • A protection tunnel (LSP/L2TP tunnel) is set up between the master and backup LACs.
Figure 1 Dual-device hot backup

Process of Dual-Device Hot Backup

The process of dual-device hot backup is as follows:

  1. A terminal is connected to Master 1 (master LAC) through PPPoE dialup.

  2. Master 1 (master LAC) performs PPP LCP negotiation and PAP/CHAP authentication with the terminal.

  3. Master 1 (master LAC) sends an authentication request to the LAC-side RADIUS server. After the terminal is authenticated, Master 1 (master LAC) establishes a tunnel with the LNS.

  4. Master 1 (master LAC) sends backup tunnel information to Master 2 (backup LAC), and Master 2 (backup LAC) stores the tunnel data locally.

  5. Master 1 (master LAC) establishes a session with the LAC-side RADIUS server and sends user authentication information and PPP negotiation parameters to the server.

  6. The LNS sends an authentication request to the LNS-side RADIUS server, and the authentication succeeds.

  7. Master 1 (master LAC) sends backup session information to Master 2 (backup LAC), and Master 2 (backup LAC) stores the session data locally.

  8. Master 1 (master LAC) establishes a local PPP session with Master 2 (backup LAC) and backs up PPP user information.

  9. Master 1 (master LAC) sends Hello messages to the LNS and copies the received Hello messages to Master 2 (backup LAC). Master 2 (backup LAC) then updates the tunnel control sequence number.

Parent Topic: Understanding L2TP Access
Copyright © Huawei Technologies Co., Ltd.
Copyright © Huawei Technologies Co., Ltd.
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