
Operation Manual – IPv4 Routing
H3C S3610&S5510 Series Ethernet Switches
Chapter 4 IS-IS Configuration
4-16
After reestablishing a neighbor relationship, the GR Restarter will synchronize the
LSDB and exchange routing information with all adjacent GR capable neighbors. After
that, the GR Restarter will update its own routing table and forwarding table based on
the new routing information and remove the stale routes. In this way, the IS-IS routing
convergence is complete.
III. Management tag
Management tag carries the management information of the IP address prefixes and
BGP community attribute. It controls the redistribution from other routing protocols.
IV. LSP fragment extension
IS-IS advertises link state information by flooding LSPs. One LSP carries limited
amount of link state information; therefore, 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 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
z
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.
z
System ID
The system ID of the originating system.
z
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.
z
Virtual System
Virtual System is identified by the additional system ID and generates extended LSP
fragments.
z
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.