Alcatel-Lucent 7750 SR OS - Manual (Page 21)

IP Router Configuration
7750 SR OS Router Configuration Guide Page 21
System Interface
The system interface is associated with the network entity (such as a specific router or switch), not
a specific interface. The system interface is also referred to as the loopback address. The system
interface is associated during the configuration of the following entities:
• The termination point of service tunnels
• The hops when configuring MPLS paths and LSPs
• The addresses on a target router for BGP and LDP peering
The system interface is used to preserve connectivity (when routing reconvergence is possible)
when an interface fails or is removed. The system interface is used as the router identifier. A
system interface must have an IP address with a 32-bit subnet mask.