H3C Technologies H3C SR8800 - Manual (Page 166)

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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 a
router connected to the originating system in the network, but the virtual systems are reachable
through the originating system only. The IS-IS routers not supporting LSP fragment extension
can operate properly without modifying the extended LSP fragments received, but some
limitation is imposed on the link state information in the extended LSP fragments advertised by
the virtual systems.
{
Mode-2
Applicable to a network where all the routers support LSP fragment extension. In this mode, all
the IS-IS routers know which virtual system belongs to which originating system; no limitation is
imposed on the link state information of the extended LSP fragments advertised by the virtual
systems.
The operation mode of LSP fragment extension is configured based on area and routing level.
Mode-1 allows the routers supporting and not supporting LSP fragment extension to interoperate
with each other, but it restricts the link state information in the extended fragments. Mode-2 does
not restrict the link state information in the extended fragments, and is recommended for an area
where all the routers are at the same routing level and support LSP fragment extension.
Dynamic host name mapping mechanism
The dynamic host name mapping mechanism provides the mappings between the host names and the
system IDs for the IS-IS routers. The dynamic host name information is announced in the dynamic host
name CLV of an LSP.
This mechanism also provides the mapping between a host name and the DIS of a broadcast network,
which is announced in the dynamic host name TLV of a pseudonode LSP.
A host name is easier to remember than a system ID. After enabling this feature on the router, you can see
the host names instead of system IDs using the display command.
BFD
NOTE:
For more information about BFD, see High Availability Configuration Guide.
Bidirectional forwarding detection (BFD) provides a single mechanism to quickly detect any link failures
between IS-IS neighbors to reduce network convergence time.
Protocols and standards
• ISO 10589 ISO IS-IS Routing Protocol
• ISO 9542 ES-IS Routing Protocol
• ISO 8348/Ad2 Network Services Access Points
• RFC 1195, Use of OSI IS-IS for Routing in TCP/IP and Dual Environments
• RFC 2763, Dynamic Hostname Exchange Mechanism for IS-IS
• RFC 2966, Domain-wide Prefix Distribution with Two-Level IS-IS
• RFC 2973, IS-IS Mesh Groups
• RFC 3277, IS-IS Transient Blackhole Avoidance
• RFC 3358, Optional Checksums in ISIS