R3303-HP HSR6800 Routers Layer 3 - IP Routing Configuration Guide

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• In IRF mode, NSR backs up IS-IS link state information from the global active MPU to the global
standby MPU. When a global active/standby MPU switchover occurs, NSR can complete link state
recovery and route regeneration without requiring the cooperation of other devices.
IS-IS TE
IS-IS traffic engineering (TE) creates and maintains the Label Switched Path (LSP).
When creating the Constraint-based Routed LSP (CR LSP), MPLS must get the traffic attributes of all links
in the local area. The traffic engineering information of links is obtained from IS-IS. For more information
about configuring IS-IS TE, see MPLS Configuration Guide.
Management tag
Management tag simplifies routing information management by carrying the management information
of the IP address prefixes (to control route redistribution from other routing protocols) and BGP community
and extended community attributes.
LSP fragment extension
IS-IS advertises link state information by flooding LSPs. Because one LSP carries a limited amount of link
state information, IS-IS fragments LSPs. Each LSP fragment is uniquely identified by a combination of the
System ID, Pseudonode ID (0 for a common LSP or a non-zero value for a Pseudonode LSP), and LSP
Number (LSP fragment number) of the node or pseudo node that generated the LSP. The one-byte LSP
Number field, allowing a maximum of only 256 fragments to be generated by an IS-IS router, limits the
amount of link information the IS-IS router can advertise.
The LSP fragment extension feature allows an IS-IS router to generate more LSP fragments. Up to 50
additional virtual systems can be configured on the router, and each virtual system is capable of
generating 256 LSP fragments to enable the IS-IS router to generate up to 13056 LSP fragments.
• Terms:
{ Originating system—The router actually running IS-IS. After LSP fragment extension is enabled,
additional virtual systems can be configured for the router. Originating system is the IS-IS
process that originally runs.
{ System ID—The system ID of the originating system.
{ Additional system ID—Additional virtual system IDs are configured for the IS-IS router after LSP
fragment extension is enabled. Each additional system ID can generate 256 LSP fragments.
Both the additional system ID and the system ID must be unique in the entire routing domain.
{ Virtual system—A virtual system is identified by an additional system ID and generates
extended LSP fragments.
{ Original LSP—The LSP generated by the originating system. The system ID in its LSP ID field is
the system ID of the originating system.
{ Extended LSP—Extended LSPs are generated by virtual systems. The system ID in its LSP ID field
is the virtual system ID. After additional system IDs are configured, an IS-IS router can advertise
more link state information in extended LSP fragments. Each virtual system can be considered a
virtual router. An extended LSP fragment is advertised by a virtual system identified by an
additional system ID.
• Operation modes:
The LSP fragment extension feature operates in the following modes:
{ Mode-1—Applicable to a network where some routers do not support LSP fragment extension.
In this mode, adjacencies are formed between the originating system and virtual systems, with
the link cost from the originating system to each virtual system as 0. Each virtual system acts as