Alcatel-Lucent 7450 Configuration Manual page 116

Router Global Commands
If one or more LSPs in the ECMP set of a prefix do not have a weight configured, the regular ECMP
spraying for the prefix will be performed.
The weight assigned to an LSP impacts only the forwarding decision, not the routing decision. In
other words, it does not change the selection of the set of ECMP tunnel next-hops of a prefix when
more next-hops exist than the value of the router ecmp option. Once the set of tunnel next-hops is
selected, the LSP weight is used to modulate the amount of packets forwarded over each next-hop. It
also does not change the hash routine, but only the spraying of the flows over the tunnel next-hops is
modified to reflect the normalized weight of each tunnel next-hop.
The no version of the command resumes regular ECMP spraying of packets of IGP, BGP, and static
route prefixes over MPLS LSP.
fib-priority
Syntax fib-priority {high | standard}
Context config>router
Description This command specifies the FIB priority for VPRN.
icmp-tunneling
Syntax icmp-tunneling
no icmp-tunneling
Context config>router
Description This command enables the tunneling of ICMP reply packets over MPLS LSP at a LSR node as per
RFC 3032.
The LSR part of this feature consists of crafting the reply ICMP packet of type=11- 'time exceeded',
with a source address set to a local address of the LSR node, and appending the IP header and leading
payload octets of the original datagram. The system skips the lookup of the source address of the
sender of the label TTL expiry packet, which becomes the destination address of the ICMP reply
packet. Instead, CPM injects the ICMP reply packet in the forward direction of the MPLS LSP the
label TTL expiry packet was received from. The TTL of pushed labels should be set to 255.
The source address of the ICMP reply packet is determined as follows. The LSR uses the address of
the outgoing interface for the MPLS LSP. Note that with LDP LSP or BGP LSP multiple ECMP
next-hops can exist and in such a case the first outgoing interface is selected. If that interface does not
have an address of the same family (IPv4 or IPv6) as the ICMP packet, then the system address of the
same family is selected. If one is not configured, the packet is dropped.
When the packet is received by the egress LER, it performs a regular user packet lookup in the data
path in the GRT context for BGP shortcut, 6PE, and BGP label route prefixes, or in VPRN context
for VPRN and 6VPE prefixes. It then forwards it to the destination, which is the sender of the original
packet which TTL expired at the LSR.
Page 116 7450 ESS Router Configuration Guide