Damping Shorter Physical Interface Transitions
By default, when an interface changes from being up to being down, or from down to up, this transition is advertised immediately to the hardware and Junos OS. In some situations—for example, when an interface is connected to an add/drop multiplexer (ADM) or wavelength-division multiplexer (WDM), or to protect against SONET/SDH framer holes—you might want to damp interface transitions. This means not advertising the interface’s transition until a certain period of time has passed, called the hold-time. When you have damped interface transitions and the interface goes from up to down, the down hold-time timer is triggered. Every interface transition that occurs during the hold-time is ignored. When the timer expires and the interface state is still down, then the router begins to advertise the interface as being down. Similarly, when an interface goes from down to up, the up hold-time timer is triggered. Every interface transition that occurs during the hold-time is ignored. When the timer expires and the interface state is still up, then the router begins to advertise the interface as being up. For information about physical interface damping, see Physical Interface Damping Overview.
This task applies to damping shorter physical interface transitions in milliseconds. To damp longer physical interface transitions in seconds, see Damping Longer Physical Interface Transitions.
To configure damping of shorter physical interface transitions:
- Select the interface to damp, where the interface name
is interface-type-fpc/pic/port:user@host# edit interfaces interface-name
- Configure the hold-time for link up and link down.[edit interfaces interface-name]user@host# set hold-time up milliseconds down milliseconds
The hold time can be a value from 0 through 4,294,967,295 milliseconds. The default value is 0, which means that interface transitions are not damped. Junos OS advertises the transition within 100 milliseconds of the time value you specify.
For most Ethernet interfaces, hold timers are implemented using a one-second polling algorithm. For 1-port, 2-port, and 4-port Gigabit Ethernet interfaces with small form-factor pluggable transceivers (SFPs), hold timers are interrupt-driven.
The hold-time option is not available for controller interfaces.