the echo replies indicates to the sending router that no label mapping exists on the
receiving router.)
The
ping mpls
commands perform a basic connectivity check. When the echo request
exits the tunnel at the egress LSR, the LSR sends the packet to the control plane. The
egress router validates the FEC stack to determine whether that LSR is the actual
egress for the FEC. The egress router sends an echo reply packet back to the source
address of the echo request packet. The egress router can send the packet back by
means of either the IP path or the MPLS path.
The
trace mpls
commands isolate faults in the LSP. For these commands, successive
echo request packets are sent along the path. The first packet has a TTL of one; the
TTL value is incremented by one for each successive packet. The first packet therefore
reaches only the next hop on the path; the second packet reaches the next router
after that. Echo request packets are sent until either an echo reply is received from
the egress router for the FEC or a TTL of 32 is reached.
When a TTL expires on an LSR, that LSR sends an echo reply packet back to the
source. For transit routers, the echo reply indicates that downstream mapping exists
for the FEC, meaning that the packet would have been forwarded if the TTL had not
expired. The egress router sends an echo reply packet verifying that it is the egress.
Although you cannot send IPv6 UDP packets for MPLS ping, you can use the
ping
mpls l3vpn
command with an IPv6 prefix to investigate IPv6 VPNs.
Related Topics
■
ECMP Labels for MPLS on page 233
■
Verifying and Troubleshooting MPLS Connectivity on page 363
■
Packet Flow Examples for Verifying MPLS Connectivity on page 365
■
ping mpls ip
■
ping mpls l2transport
■
ping mpls l3vpn
■
ping mpls rsvp tunnel
■
ping mpls vpls
■
trace mpls ip
■
trace mpls l2transport
■
trace mpls l3vpn
■
trace mpls rsvp tunnel
■
trace mpls vpls
LDP Discovery Mechanisms
LDP uses two different mechanisms for peer discovery. Peer discovery removes the
need to explicitly configure the label-switching peers for an LSR.
236
■
LDP Discovery Mechanisms
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Страница 346: ...310 Example Traffic Class Configuration for Differentiated Services JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 535: ...There is no no version See undebug ip mbgp Monitoring BGP MPLS VPNs 499 Chapter 5 Configuring BGP MPLS Applications...
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Страница 538: ...502 Layer 2 Services Over MPLS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 592: ...556 Multiple ATM Virtual Circuits over a Single Pseudowire Example JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 604: ...568 Virtual Private LAN Service JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 618: ...582 VPLS References JUNOSe 11 0 x BGP and MPLS Configuration Guide...
Страница 642: ...606 VPLS Configuration Example with LDP Signaling JUNOSe 11 0 x BGP and MPLS Configuration Guide...
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Страница 718: ...682 Monitoring MPLS Forwarding Table for VPWS JUNOSe 11 0 x BGP and MPLS Configuration Guide...
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