Main Link With A Cisco Router With L2Tp - Teldat -3Ge-USB User Manual

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those in the event syslog pattern command.

12.2 Main link with a Cisco router with L2TP

To configure the link as a main link through the Teldat-3Ge-USB. Here, the Cisco default route is the Virtual-ppp in-
terface, which connects to the mobile network through the Teldat-3Ge-USB.
Note
This only applies if using L2TP, not PPPoE.
If idle time is configured in the Vitural-ppp interface in a Cisco router, when this times out, the router drops the PPP
connection and then immediately enables it again (even if there is no important traffic). Consequently, we have to
add to the Cisco configuration to resolve this. The additional configuration ensures that the router, once the idle time
has timed out and the link dropped, automatically puts the Virtual-ppp interface into shutdown. The Virtual-ppp inter-
face remains in shutdown until traffic begins to arrive again and communications through the Teldat-3Ge-USB are
needed once more. If we don't do this, the connection remains permanently active without traffic to justify this.
So a drop in the PPP link can be detected, use a Cisco feature known as EEM ( Embedded Event Manager) and
monitor the Virtual-ppp interface for a drop. When this occurs change the Virtual-ppp interface state to shutdown, so
the connection to the Teldat-3Ge-USB doesn't activate again.
To detect the presence of important traffic in the Cisco router (so the connection to the mobile network, through a
Teldat-3Ge-USB, must reestablish) enable packet drop events in the Cisco configuration. Consequently, if this event
appears, the Virtual-ppp interface state changes from shutdown to active.
The commands to add are as follows:
• To make the Virtual-ppp interface become the Cisco router's default route:
ip route 0.0.0.0 0.0.0.0 Virtual-PPP1
• To ensure the Virtual-PPP interface has an idle time configured, enter the following command in the Virtual-ppp in-
terface configuration:
ppp timeout idle 180
• So the Virtual-ppp interface changes its state to shutdown once idle time has timed out:
!
event manager applet ETHANT-DOWN
event syslog pattern "Interface Virtual-PPP1, changed state to down"
action 1.0 cli command "enable"
action 1.1 cli command "debug ip cef drops"
action 1.2 cli command "conf te"
action 1.3 cli command "interface virtual-ppp1"
action 1.4 cli command "shutdown"
action 1.5 cli command "exit"
action 1.6 cli command "exit"
action 1.7 cli command "exit"
!
• So the Virtual-ppp interface enables again once there is important traffic, we need to preenable events triggering
incidents where the router drops a packet because it can't find an exit route ( action 1.1 cli command "debug ip cef
drops").
!
event manager applet ETHANT-UP
event syslog pattern "No route"
action 1.0 cli command "enable"
action 1.1 cli command "conf te"
action 1.2 cli command "interface virtual-ppp1"
action 1.3 cli command "no shutdown"
action 1.4 cli command "exit"
action 1.5 cli command "exit"
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