Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) User Manual
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Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide
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IP Traceroute over MPLS
1
1 <1 ms <1 ms <1 ms 10.51.3.7
2 <1 ms <1 ms <1 ms 10.56.1.2
3 <1 ms <1 ms <1 ms 10.52.10.4
4 <1 ms <1 ms <1 ms 10.34.22.8
5 <1 ms <1 ms <1 ms 10.1.3.8
In this scenario, IP traceroute over MPLS behaves just like the standard traceroute command. At
each hop, ICMP messages are generated and returned to the destination (source CE1) as regular
IP packets through standard IP routing protocols. The user gets the same traceroute behavior when
the user disables the IP Traceroute over MPLS feature with the no ip icmp mpls-response
command before sending a traceroute probe. When the ICMP response is disabled, the standard
traceroute implementation is used.
Scenario B - Layer 3 VPN over MPLS
MPLS is enabled in the provider core. Customer traffic is routed through the provider network using
a Layer 3 VPN. The egress PE is a Brocade NetIron CER or a Brocade NetIron CES
1. Issue the ip icmp mpls-response command with the no-label-extension option on each LSR
(R1, R2, R3, and R4).
Brocade# configure terminal
Brocade(config)# ip icmp mpls-response no-label-extension
2. On CE 1 (IP address 10.3.3.3), issue the traceroute command with the destination address of
CE2 (IP address 10.1.3.8).
CE1# traceroute 10.1.3.8
Type Control-c to abort
Tracing the route to IP node (10.1.3.8) from 1 to 30 hops
1 <1 ms <1 ms <1 ms 10.51.3.7
2 * * * ?
3 * * * ?
4 * * * ?
5 <1 ms <1 ms <1 ms 10.1.3.8
The outcome is the same as if the user were using the default configuration (
). Only PE1 and CE2 return traceroute information. ICMP error messages
generated at R2, R3, and PE2 with subsequent probes are dropped, because these routers can
only use LSPs to transport traffic and using LSP is blocked. Traceroute prints an asterisk (*) for
each dropped package. The fifth traceroute probe makes it to C2, which routes a destination
unreachable message back to CE1 using IP routing lookup. Refer to the
for more
information.
Tracing a route across an MPLS domain with label extensions disabled and
use-lsp enabled
Assumptions: MPLS is enabled in the provider core. Only the PEs have IP routes to the CEs. The
MPLS response default configuration is enabled on all routers in the MPLS domain. The example
specifies LSP forwarding but suppresses label stack information. CE1 is sending a traceroute to
CE2 with a destination IP address of 10.1.3.8.