Juniper JUNOSE SOFTWARE 11.0.X - LINK LAYER CONFIGURATION GUIDE 4-1-2010 Configuration Manual page 489

2.
3.
hdlc down-when-looped
hdlc keepalive
hdlc shutdown
host1(config-if)#hdlc keepalive 10
Enable loopback detection on an interface.
host1(config-if)#hdlc down-when-looped
Disable an interface.
host1(config-if)#hdlc shutdown
Use to enable loopback detection on a Cisco HDLC interface.
By default, loopback detection is disabled.
Example
host1(config-if)#hdlc down-when-looped
Use the no version to disable loopback detection on a Cisco HDLC interface.
See hdlc down-when-looped.
Use to specify the keepalive timeout value.
When the keepalive timer expires, the interface increments its own counter;
then it compares the value of this counter with the last value received from a
peer. If the difference between the values of the two counters is greater than
three, the Cisco HDLC interface is declared down. After that, the interface sends
a keepalive message containing the value of its counter and the last received
value of the peer's counter.
The router stores the values received in keepalive messages from a peer interface.
If the interface is down, the router compares the received value of its own counter
with the value from the peer. If the difference between the values of the two
counters is less than four, the router declares the interface to be up. Both sides
have to configure the same value for the keepalive interval.
If the keepalive interval is 10 seconds, then a failed link is detected between 30
and 40 seconds after failure.
The range is 0–6553 seconds. A value of 0 turns keepalive off.
The default is 10 seconds.
Example
host1(config-if)#hdlc keepalive 10
Use the no version to turn off the keepalive feature.
See hdlc keepalive.
Chapter 14: Configuring Cisco HDLC
Configuration Tasks
459