HPE 5800 Series Configuration Manual page 134

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Obtain IS-IS neighbor information without changing adjacencies.
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Obtain the LSDB.
To complete these tasks, the GR Restarter sends an OSPF GR signal to GR Helpers so that the GR
Helpers keep their adjacencies with the GR Restarter, and restores the neighbor table after receiving
responses from neighbors. The GR Restarter then synchronizes the LSDB with all GR-capable
neighbors, calculates routes, updates its routing table and forwarding table, and removes stale
routes. The IS-IS routing convergence is then complete.
IS-IS NSR
NSR is a new feature that overcomes the application limit of GR. It backs up IS-IS link state
information from the master device to the slave device. When a master/slave occurs, NSR can
complete link state recovery and route re-generation 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.
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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.
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