3Com MSR 50 Series Configuration Manual page 890

890 C 57: IS-IS C
HAPTER ONFIGURATION
(0 for a common LSP or non-zero for a Pseudonode LSP), and LSP Number (LSP
fragment number) of the node or pseudo node that generated the LSP. The 1-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 that 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,
with each virtual system capable of generating 256 LSP fragments, to enable the
IS-IS router to generate up to 13056 LSP fragments.
1 Terms
Originating System
■
It is 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 actual IS-IS process that originally runs.
System-ID
■
The system ID of the Originating System.
Additional System-ID
■
It is the additional virtual system ID 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
■
Virtual System is identified by the additional system ID and generates extended LSP
fragments
Original LSP
■
It is 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
■
It is the LSP generated by a virtual system. 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 as a virtual router. An extended LSP fragment is advertised by a virtual
system identified by additional system ID.
2 Operation modes
The LSP fragment extension feature operates in two modes on an IS-IS router: