Juniper JUNOSE, Configuration Manual

Page: 271 / 738

Table 25: Sub-TLVs Supported for the Target FEC Stack TLV
Comments Value Subtype Number
– LDP IPv4 prefix 1
– LDP IPv6 prefix 2
– RSVP IPv4 LSP 3
– VPN IPv4 prefix 6
– VPN IPv6 prefix 7
For VPLS and VPWS L2 VPN endpoint 8
For Martini encapsulation FEC 128 pseudowire 10
Related Topics
■
MPLS Label Switching and Packet Forwarding on page 209
MPLS Connectivity Verification and Troubleshooting Methods
In IP networks, the ping and traceroute commands enable you to verify network
connectivity and find broken links or loops. In MPLS-enabled networks, you can use
the
ping command to determine whether IP connectivity exists to a destination even
when the ping packets must traverse multiple LSPs. You can use the traceroute
command to determine the labels that data packets use when traversing LSPs to the
destination.
In an MPLS-enabled network, however, you cannot use these IP commands to
determine MPLS connectivity to a destination.
You can use the MPLS ping and trace features to detect data plane failures in LSPs.
Specific
mpls ping and trace mpls commands enable you to target different types
of MPLS applications and network topologies. The various ping mpls and trace mpls
commands send UDP packets, known as MPLS echo requests, to the egress LSR of
MPLS packets in a given FEC. Each echo request is forwarded along the same data
path as the MPLS packets in that FEC.
The echo request packets use a destination address in the 127.0.0.0/8 range and
port 3503. The default address is 127.0.0.1. This address range prevents IP from
forwarding the packet, so that the echo request must follow the MPLS data path. This
behavior is different from that of the IP
ping and traceroute commands, which send
ICMP packets to the actual destination.
Each MPLS echo request packet contains information about the FEC stack that is
being validated. LSRs that receive an MPLS echo request respond with MPLS echo
reply packets. (Even when MPLS is not enabled on that router, echo reply packets
are sent by E Series routers that receive an echo request packet. This situation is a
transient condition when the router is receiving labeled packets. A return code in
MPLS Connectivity Verification and Troubleshooting Methods
■ 235
Chapter 2: MPLS Overview