Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 233)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 209
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IP Traceroute over MPLS
1
9. CE1 sends a forth traceroute probe with a TTL value of 4. The packet is label-switched until it
arrives at PE2 with a TTL value of 1. PE2 drops the packet and generates an ICMP ttl-exceeded
message without label stack extension.
Traceroute reports only the IP address of PE2. There is no label stack to report. R3 popped the
outer label before passing the traceroute packet on to PE2, and the Brocade egress router
pops the VPN label before sending the ICMP message back to CE1
4 <1 ms <1 ms <1 ms 10.34.22.8
5 <1 ms <1 ms <1 ms 10.1.3.8
10. The fifth traceroute probe has a TTL large enough (TTL=5) for the packets to reach CE2. CE2
generates an ICMP destination unreachable message, which CE2 sends back to CE1.
Traceroute reports only the IP address of the destination device CE2. No label extension is
added because the received packet is not labeled. The destination unreachable message is
label-switched back as a normal data packet.
5 <1 ms <1 ms <1 ms 10.1.3.8
Configuring Traceroute over MPLS
The ip icmp mpls-response command configures the behavior of the traceroute operation by
controlling both the ICMP message format (use ICMP label stack extensions or not) and the manner
in which the ICMP messages are forwarded through an MPLS domain (by way of IP routing table
lookup or through label-switching using LSPs).
The command is accessible in global configuration mode.
MPLS response is enabled by default. To enable the MPLS response after it was disabled, enter the
following command:
Brocade(config)# ip icmp mpls-response
To specify using LSP to forward the ICMP messages with MPLS label extensions, enter the following
command:
Brocade(config)# ip icmp mpls-response use-lsp
To specify generating ICMP messages without MPLS label extensions, enter the following
command:
Brocade(config)# ip icmp mpls-response no-label-extensions
To disable the IP Traceroute over MPLS feature, enter the following command:
Brocade(config)# no ip icmp mpls-response
Syntax: [no] ip icmp mpls-response [use-lsp] [no-label-extension]
The mpls-response parameter enables the ICMP MPLS response in default mode. The feature is
enabled by default and configured to use IP routing to forward ICMP messages.
The use-lsp parameter, specifies to forward ICMP error messages based on information encoded in
the label stack along the LSPs configured for the MPLS domain. LSP use is disabled by default.
The no-label-extension parameter specifies not to use label extensions in the ICMP error messages.