LINK-3-UPDOWN vs LINEPROTO-5-UPDOWN
December 20, 2015
This post describes the difference between LINK and LINEPROTO syslog messages.
- Layer 1
- it is down in case of cable unplugged, wrong cable, shutdown command, speed mismatch (ethernet), device on the other end of cable is powered off
- Layer 2
- software handling the link claims that the interface is unusable
- if Layer 1 is down then this is also down
- if Layer 1 is up it can be down – for example if physical link works properly but ppp session can not be established (incorrect password, etc).