This is to prevent connectivity issues caused by inter-DC links flapping.
In the past this has caused at least spikes of 503s.
The goal is to apply interface damping only on the primary link between 2 sites, where we at least have 2 backup options. That way we minimize the risk of multiple links being down at the same time.
Zayo link between codfw-eqiad
Zayo link between codfw-ulsfo
Level3 link between eqiad-esams
```
damping {
enable;
max-suppress 600; # Even if still flapping, re-enable interface after 10min (and start counters over)
suppress 2000; # Counter increase by 1000 at each flap, keep interface down when reached 2000
half-life 15; # Reduce by half the penalty counter after 15s
reuse 100; # Interface up when counter falls bellow 100
}
```
Example counters (and states), after 2 flaps in less than 15s, stable after:
5s =2000 (down), 15s = 1000, 30s = 500, 45s = 250, 1min = 125, 1m15 = 75 (back up)
if re-flap after 30s:
5s =2000 (down), 15s = 1000, 30s = 500, 35s = 1500, 45s = 750, 1min = 375, 1m15 = 187,5, 1m30 = 93 (back up)
etc.
In term of monitoring, the interfaces will report as down, which should be alerted on by our existing Icinga checks.
More doc:
https://www.juniper.net/documentation/en_US/junos/topics/concept/physical-interface-damping.html
https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/damping-edit-interfaces.html