Feature Behavior - Alcatel-Lucent 7450 Configuration Manual

Weighted Load Balancing IGP, BGP, and Static Route Prefix Packets over IGP Shortcut
The user can also disable specific MPLS LSPs from being used in IGP shortcut or forwarding
adjacency by configuring the following:
configure>router>mpls>lsp>no igp-shortcut
The user enables the weighted load balancing feature using the following new router level
command:
configure>router>weighted-ecmp
When this command is enabled, packets of IGP, BGP, and static route prefixes resolved to
a set of ECMP tunnel next-hops are sprayed proportionally to the weights configured for
each MPLS LSP in the ECMP set.
The user can configure a weight for each LSP using the following command:
configure>router>mpls>lsp>load-balancing-weight <32-bit-integer>
For an auto-LSP signaled via an LSP template, the weight is configured using the
following command:
configure>router>mpls>lsp-template>load-balancing-weight <32-bit-integer>
There is no default weight value for an LSP. If one or more LSP in the ECMP set of a
prefix does not have a weight configured, the regular ECMP spraying for the prefix will be
performed. The user entered weight is normalized to the closest integer value which
represents the number of entries in the ingress prefix hash table assigned to the LSP for the
purpose of spraying packets of all prefixes resolved to this LSP. The higher the normalized
weight, the more entries will be assigned to the LSP, the more packets will be sent to this
LSP.

Feature Behavior

This section describes the details of the behavior of the weighted load-balancing feature for IGP,
BGP, and static route prefixes resolved in RTM to IGP shortcuts.
When an IGP, BGP, or a static route prefix is resolved in RTM to a set of ECMP tunnel next-hops
of type RSVP-TE and the router level weighted-ecmp option is enabled, the ingress hash table for
the next-hop selection is populated with a number of tunnel next-hop entries for each LSP equal to
the normalized LSP weight value. All prefixes resolving to the same set of ECMP tunnel next-hops
use the same table.
This feature follows the following procedures:
Page 54 7450 ESS Router Configuration Guide