Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 621)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 597
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IS-IS shortcuts
5
Displaying show command
These commands display the configuration.
Brocade(config)# show running config
Brocade(config)# show ip bgp config
To check BGP next hop resolution and the IGP cost for the next hop, use this show command.
Brocade(config)# show ip bgp next-hop
This command checks the RTM entry cost value to determine whether BGP next hop resolution
takes the IGP cost value, compare to MPLS LSP metric value.
Brocade(config)# show ip route
IS-IS shortcuts
This section describes IS-IS shortcuts and how to configure them on an MPLS router with traffic
engineering (TE) capabilities.
Overview
The IS-IS Shortcuts feature enables an MPLS TE path (LSP tunnel) to serve as a shortcut through
the network to a destination based on the cost of the path (metric). Traffic is forwarded through the
LSP tunnel to destinations within the IS-IS routing domain. This feature helps optimize available
bandwidth by choosing paths using LSPs where multiple paths exist to the same destination.
When IS-IS shortcuts are enabled on an LSP tunnel, IS-IS includes the LSP in the SPF calculation.
When IS-IS determines that the LSP shortcut is the best path to a destination, it adds the route to
the IP routing table, specifying the LSP tunnel interface as the outbound interface, including the
cost of the LSP. Only LSPs configured to a router ID are considered as shortcuts. When the LSP
goes down or is administratively disabled, or when the shortcuts isis command is removed from the
configuration, the IS-IS LSP tunnel routes are removed from the main routing table.
Determining the cost of an IS-IS shortcut
IS-IS uses the following information to determine the cost of an IS-IS shortcut:
• The announce metric, when announce is enabled
• When announce is not enabled and “ignore-lsp-metric” is not configured, IS-IS uses the LSP
metric configured under the LSP configuration mode, for example:
Brocade(config-mpls-lsp)# metric value
• When no LSP metric is configured, IS-IS uses the native IGP cost, plus or minus the relative
metric
• When there is no relative metric, IS-IS uses the native IGP cost