HP VPN Firewall Appliances Appendix Protocol Reference

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{ 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
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 correctly 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 by using the display command.
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