mapping TLV. This TLV contains all the downstream mappings of the LSR on which the
TTL expired, if that feature is supported by the LSR. You can use the detail version of the
trace mpls commands to display these downstream mappings.
Supported TLVs
Table 51 on page 243 lists the TLVs supported by the MPLS LSP ping feature. Table 52 on
page 244 lists the sub-TLVs supported for the Target FEC Stack TLV.
Table 51: TLVs Supported by MPLS LSP ping
CommentsValueType Number
Multiple FEC stack sub-TLVs are not supported.
A single LSP ping message cannot have more than
one target FEC stack TLV.
Target FEC Stack1
Only the IPv4 (numbered or unnumbered)
downstream address type is supported.
Flag I for the Interface and Label Stack object is
supported. Flag N, to treat the packet as a non-IP
packet, is not supported.
An MPLS LSP trace echo request includes this TLV.
This TLV contains the downstream address
all-routers-multicast; that is the well-known IP
address 224.0.0.2. Validation of the downstream
address is not performed.
Verification of the downstream address is not
performed on receipt of an MPLS echo request
that contains this TLV.
In an MPLS echo reply, multipath information is
not supported in this TLV; the multipath type is
always set to 0 in the reply. However, the reply
includes one downstream mapping TLV for each
downstream path.
Downstream Mapping2
This TLV is included in the MPLS echo request
packet. The TLV can specify either “ Do not reply”
or “ Reply via an IPv4/IPv6 UDP packet.”
Pad3
This TLV is generated if requested by the received
downstream mapping TLV.
Interface and Label Stack7
This TLV is generated if an error is encountered
while parsing one of the received TLVs.
Errored TLVs9
–Reply TOS Byte10
243Copyright © 2010, Juniper Networks, Inc.
Chapter 3: MPLS Overview
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