Configuring A Logical Interface For A Persistent Backup; Connection - HP 7102dl - ProCurve Secure Router Configuration Manual

Configuring Backup WAN Connections
Configuring a Persistent Backup Connection
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Configuring a Logical Interface for a Persistent Backup

Connection

Although a backup connection provides redundancy for a primary WAN con-
nection such as a Frame Relay connection or an ISP connection, it does not
duplicate the primary WAN connection. The backup connection is ultimately
to the same peer, but it is established through a different path in the PSTN or
PTT infrastructure. For example, Frame Relay running over an E1- or T1-carrier
line establishes a fixed path through the PSTN or PTT infrastructure. If that
connection is lost, the backup connection must be established using a different
path through the PSTN or PTT infrastructure. (See Figure 3-14.)
ISDN
Router A
E1
Figure 3-14. Backing Up a Frame Relay Connection
The dial-up connection through the physical PSTN or PTT network needs a
Data Link Layer protocol to establish the new link and regulate the flow of
data. Just as for any other WAN connection on the ProCurve Secure Router,
you configure the Data Link Layer protocols in a logical interface. However,
unlike for ADSL, T1, and E1 connections, you do not explicitly bind the backup
line to a logical interface. Instead, you configure a backup logical interface,
which you then map to the logical interface for the primary connection. When
the primary interface goes down, the backup interface establishes a connec-
tion using whatever backup line is available.
On the ProCurve Secure Router, PPP provides the Data Link Layer for persis-
tent backup connections. You configure a backup PPP interface no matter
what type of Data Link Layer protocol, including Frame Relay or Asynchro-
nous Transfer Mode (ATM) (which is used for ADSL connections), is used for
the primary connection.
PTT
ISDN
Frame Relay
network E1
E1
Router C
Router B