IP Router Configuration
Router Configuration Guide 47
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:
1. MPLS populates the user configured LSP weight in TTM. When the global command
weighted-ecmp is enabled, and if one or more LSPs in the ECMP set of a prefix does
not have a weight configured, the regular ECMP spraying for the prefix will be
performed.
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