Cisco ASR 900 Series User Manual

Table 5: MPLS LSP Traceroute Example
Device ActionMPLS Packet Type and
Description
DeviceStep
•
Sets the TTL of the label
stack to 1.
•
Sends the request to
LSR2.
MPLS echo request—With a
target FEC pointing to LSR4
and to a downstream mapping.
LSR1
1
Receives packet with TTL = 1.
•
Processes the UDP packet
as an MPLS echo request.
•
Finds a downstream
mapping, replies to LSR1
with its own downstream
mapping based on the
incoming label, and sends
a reply.
MPLS echo reply.LSR2
1
•
Sets the TTL of the label
stack to 2.
•
Sends the request to
LSR2.
MPLS echo request—With the
same target FEC and the
downstream mapping received
in the echo reply from LSR2.
LSR1
1
Receives packet with TTL = 2.
•
Decrements the TTL.
•
Forwards the echo request
to LSR3.
MPLS echo request.LSR2
1
Receives packet with TTL = 1.
•
Processes the UDP packet
as an MPLS echo request.
•
Finds a downstream
mapping and replies to
LSR1 with its own
downstream mapping
based on the incoming
label.
MPLS reply packet.LSR3
1
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
67
MPLS LSP Ping, Traceroute, and AToM VCCV
MPLS LSP Traceroute Operation

Cisco ASR 900 Series Specifications

General

Brand	Cisco
Model	ASR 900 Series
Category	Network Router
Language	English