Brocade Multi-Service IronWare Administration Guide (Supporting R05.6.00) - Manual (Page 226)

208 Multi-Service IronWare Administration Guide
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IPv6 Traceroute over an MPLS network
6
3 <1 ms <1 ms <1 ms 2001:DD8:300::2
MPLS Label=1029 Exp=0 TTL=1 S=0
MPLS Label=794624 Exp=0 TTL=2 S=1
4. The fourth traceroute probe (TTL=4) is forwarded until it expires at the egress provider edge
device PE2. PE2 drops the packet and generates a ttl-exceeded ICMPv6 message without label
stack extension since there is no label stack to report.
Traceroute reports only the IP address of PE2. The transit router P2 popped the outer label
before passing the traceroute packet on to the egress PE2 and PE2 pops the VPN label before
sending the ICMPv6 message back to the customer source device CE1.
4 <1 ms <1 ms <1 ms 2001:DE8:300::2
5 <1 ms <1 ms <1 ms 2001:DB8:2::2
5. The fifth traceroute probe (TTL=5) has a TTL large enough for the packets to reach the
customer destination device CE2. CE2 generates an ICMPv6 port 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 port unreachable message is
label-switched back to the customer source device CE1, as a normal data packet.
5 <1 ms <1 ms <1 ms 2001:DB8:2::2
Configuring IPv6 Traceroute over MPLS
The ipv6 icmp mpls-response command configures the behavior of the traceroute operation by
controlling both the ICMPv6 message format (use ICMPv6 label stack extensions or not) and the
manner in which the ICMPv6 messages are forwarded through an MPLS domain (by way of IP
routing table lookup or through label-switching using LSPs).
MPLS response is enabled by default. To enable the MPLS response after it was disabled, enter the
following command:
Brocade(config)# ipv6 icmp mpls-response
You can use this version of the command if the traceroute is over an IPv6-aware MPLS core. In such
a case, IPv6 traceroute uses the default option of using the routing tables to forward packets. The
IPv6 link local addresses should not be used to send the ICMPv6 packet. At the same time, you can
still use the ipv6 icmp mpls-response use-lsp command to use the configured LSPs.
To specify using LSP to forward the ICMPv6 messages with MPLS label extensions, enter the
following command:
Brocade(config)# ipv6 icmp mpls-response use-lsp
Use this version of the command if the MPLS core is non IPv6-aware, because the IPv6 forwarding
will not work.
To specify generating ICMPv6 messages without MPLS label extensions, enter the following
command:
Brocade(config)# ipv6 icmp mpls-response no-label-extensions
To disable the IPv6 Traceroute over MPLS feature, enter the following command:
Brocade(config)# no ipv6 icmp mpls-response