Figure 83: Label Encoding
Reserved Labels
Labels range from 0 through 1,048,575. Labels 0 through 999,999 are for internal use.
Some of the reserved labels (in the 0 through 15 range) have well-defined meanings.
The following reserved labels are used by EX Series switches:
•
0, IPv4 Explicit Null label—This value is legal only when it is the sole label entry (no
label stacking). It indicates that the label must be popped on receipt. Forwarding
continues based on the IP version 4 (IPv4) packet.
•
1, Router Alert label—When a packet is received with a top label value of 1, it is delivered
to the local software module for processing.
•
2, IPv6 Explicit Null label—This value is legal only when it is the sole label entry (no
label stacking). It indicates that the label must be popped on receipt.
•
3, Implicit Null label—This label is used in the control protocol (RSVP) only to request
label popping by the downstream switch. It never actually appears in the encapsulation.
Labels with a value of 3 must not be used in the data packet as real labels. No payload
type (IPv4 or IPv6) is implied with this label.
MPLS Label Operations on EX Series Switches
EX Series switches support the following label operations:
•
Push
•
Pop
•
Swap
The push operation affixes a new label to the top of the IP packet. For IPv4 packets, the
new label is the first label. The time to live (TTL) field value in the packet header is derived
from the IP packet header. The push operation cannot be applied to a packet that already
has an MPLS label.
Copyright © 2010, Juniper Networks, Inc.
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Complete Software Guide for Junos
®
OS for EX Series Ethernet Switches, Release 10.3
Summary of Contents for JUNOS OS 10.3 - SOFTWARE
Page 325: ...CHAPTER 17 Operational Mode Commands for System Setup 229 Copyright 2010 Juniper Networks Inc ...
Page 1323: ...CHAPTER 56 Operational Mode Commands for Interfaces 1227 Copyright 2010 Juniper Networks Inc ...
Page 2841: ...CHAPTER 86 Operational Commands for 802 1X 2745 Copyright 2010 Juniper Networks Inc ...
Page 3367: ...CHAPTER 113 Operational Mode Commands for CoS 3271 Copyright 2010 Juniper Networks Inc ...
Page 3435: ...CHAPTER 120 Operational Mode Commands for PoE 3339 Copyright 2010 Juniper Networks Inc ...
Page 3529: ...CHAPTER 126 Operational Mode Commands for MPLS 3433 Copyright 2010 Juniper Networks Inc ...