Interface Loopback - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - COMMAND REFERENCE A TO M 2010-10-19 Command Reference Manual

JunosE 11.3.x Command Reference Guide A to M

interface loopback

Syntax
Release Information
Description
Options
Mode
Related
Documentation
720
[ no ] interface loopback interfaceSpecifier
Command introduced before JunosE Release 7.1.0.
Defines a loopback interface, which provides a stable address for protocols (for example,
BGP, Telnet, or LDP) to use so that they can avoid any impact if a physical interface goes
down. The loopback interface sends packets back to the router or access server for local
processing. Any packets routed from the loopback interface, but not destined to the
loopback interface, are dropped. The no version deletes the loopback interface.
NOTE: Do not confuse loopback with the null 0 interface. Traffic routed to
null 0 is discarded on the line module.
You cannot shut down a loopback interface.
BEST PRACTICE: We recommend that you configure a 32-bit subnet mask
for the loopback interface. For example, if you configure a loopback interface
with the IP address and mask as 1.1.1.1/16, the 1.1.0.0/16 route entry is entered
on the line module and if no specific or longer route entry is found, all traffic
destined to the to 1.1.0.0/16 subnet is forwarded to the SRP module by the
line module. Although the SRP module responds only to traffic destined to
the 1.1.1.1 subnet and discards traffic to all other host IP addresses within that
subnet (1.1.1.1/16), if the SRP module receives too much traffic from subnets
other than 1.1.1.1, the CPU utilization on the SRP module reaches the saturation
level.
interfaceSpecifier—Particular interface; format varies according to interface type; see
Interface Types and Specifiers on page 5
Global Configuration
Configuring an MPLS Pseudowire with VCC Cell Relay Encapsulation, Configuring Local
ATM Cross-Connects with AAL5 Encapsulation, Configuring Local Cross-Connects
Between Ethernet/VLAN Interfaces, Configuring the Loopback Interface and Router ID
for BGP for L2VPNs, and Configuring the Loopback Interface and Router ID for VPLS in
the JunosE BGP and MPLS Configuration Guide
Copyright © 2010, Juniper Networks, Inc.