Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 235)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 211
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IP Traceroute over MPLS
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• IP Traceroute over MPLS supports IPv4 traceroute only.
Configuration examples
The MPLS response feature supports four different configuration options for controlling the
traceroute behavior in an MPLS domain. The command behavior varies depending on what types of
routes are configured for a given MPLS domain.
The following examples assume the same MPLS response configuration for each of the LSRs in the
MPLS domain. The user configures the MPLS response parameters per LSR, and to get consistent
traceroute behavior, it is desirable for all the LSRs in the MPLS domain to have the same settings.
Use the show running configuration command to verify the configuration.
The configuration examples refer to the topology described in Figure 1 configured with either IP
over MPLS or Layer 3 VPN over MPLS. All Layer 3 VPN examples use a Brocade NetIron CER or a
Brocade NetIron CES as the egress router.
Using IP traceroute over MPLS with the default configuration
Assumptions: The default MPLS response configuration was disabled on all LSRs in the MPLS
domain and the user re-enables the default configuration. In default mode, ICMP messages are
generated with label stack extensions and forwarded per IP routing table lookup. CE1 is tracing the
traffic path to CE2 with a destination IP address of 10.1.3.8.
Scenario A - IP over MPLS
IP over MPLS (IPoMPLS) is enabled in the provider core.
1. Re-enable the MPLS response default configuration on each LSR (R1, R2, R3, and R4).
Brocade# configure terminal
Brocade(config)# ip icmp mpls-response
2. On CE1 (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 <1 ms <1 ms <1 ms 10.56.1.2
MPLS Label=1048 Exp=7 TTL=1 S=1
3 <1 ms <1 ms <1 ms 10.52.10.4
MPLS Label=1026 Exp=7 TTL=1 S=1
4 <1 ms <1 ms <1 ms 10.34.22.8
5 <1 ms <1 ms <1 ms 10.1.3.8
The default IP over MPLS traceroute output shows a single label at hop 2 and at hop 3. Traceroute
operates like the standard implementation except that the output is enhanced with label
information. VPN labels are not used in this scenario. All ICMP error responses are routed as
normal IP packets.
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.