Juniper JUNOS OS 10.3 - XML MANAGEMENT PROTOCOL GUIDE 6-30-2010, Command Reference Manual

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interface loopback
Syntax [ no ] interface loopback interfaceSpecifier
Release Information Command introduced before JunosE Release 7.1.0.
Description 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.
Options
•
interfaceSpecifier— Particular interface; format varies according to interface type; see
Interface Types and Specifiers on page 5
Mode Global Configuration
Related Topics 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. 720
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