Avaya Configuring Dial Services Manual de usuario descargar pdf (Pagina 45)

Dial Services Overview

117353-B Rev. 00

1-17

In Figure 1-8, if the frame relay link fails at router R1, the router activates a

backup connection through the ISDN network, then back through the frame relay

network to the destination. The backup connection to the frame relay network uses

a different network interface and PVCs than the primary connection. Once the

primary line recovers and the frame relay switch responds to router R1’s DLCMI

status requests, router R1 terminates the backup connection.

Knowing When the Primary Line Fails

Depending on the protocol for the primary and backup circuit, the router

determines that the primary circuit failed in one of the following ways:

• No Breath of Life (BofL) messages in the BofL

time period

(Standard and PPP)

For Standard and PPP, the router automatically enables BofL messages on

each primary line and disables them on each backup line. BofL messages

verify that the line is operational. The router determines that the primary line

has failed when it stops receiving packets within the BofL time period.

You configure the BofL timer. For instructions, see Configuring WAN Line

Services.

• No DLCMI messages (frame relay primary/frame relay backup)

When frame relay is the protocol for the backup circuit, the router performs

link backup. For link backup, the router knows that the primary failed when it

no longer receives DLCMI messages from the switch. These messages

communicate information about the interface and the status of each PVC.

The router may also rely on modem signals to determine if the primary circuit

failed. If you rely on modem signals, you must enable the sync polling

feature, which instructs the router to monitor modem signals. (See

Configuring WAN Line Services for more information about the Sync Polling

parameter.) In addition, you must use the proper synchronous cable to connect

to the primary line’s modem or CSU/DSU. See the Cable Guide.

Note:

A primary circuit cannot use link and circuit backup simultaneously.

1 2 ... 40 41 42 43 44 45 46 47 48 49 50 ... 481 482

Sin comentarios

Avaya Configuring Dial Services Manual de usuario Pagina 45