Configuring Integrated IS-IS 343NETNetwork Entity Title (NET) indicates the network layer information, which containsno transfer layer information (SEL=0). You can regard it as a special NSAP.In general, you can configure a NET for a router. If you will redivide an area(combine multiple areas or divide an area into multiple areas), you can configuremultiple NETs to ensure correct routes in the case of reconfiguration. Because youcan configure up to three area addresses, you can only configure up to three NETs.For example, there is a NET 47.0001.aaaa.bbbb.cccc.00, in which,Area=47.0001, System ID=aaaa.bbbb.cccc, SEL=00.For example, there is a NET 01.1111.2222.4444.00, in which,Area=01, System ID=1111.2222.4444, and SEL=00.IS-IS Routing ProtocolPacketsIS-IS packets are directly encapsulated in the data link frames and mainly dividedinto 3 kinds, Hello, LSP and SNP.Hello packetsHello packets, which is also called IIH (IS-to-IS Hello PDUs), can establish andmaintain neighbor relations. The Level-1 router in a broadcast LAN forwardsLevel-1 LAN IIH; the Level-2 router in a broadcast LAN forwards Level-2 LAN IIH;non-broadcast network forwards Point-to-Point IIH.LSPLink state packet (LSP) can switch link state information. LSP can be divided intoLevel-1 LSP and Level-2 LSP. Level-2 routers transmit Level-2 LSPs; Level-1 routerstransmit Level-1 LSPs; Level-1-2 routers transmit both Level-2 LSPs and Level-1LSPs.SNPSequence Number Packet (SNP) can confirm the LSPs last received from neighbors.SNPs function as acknowledge packets, but SNPs function more validly. SNPincludes complete SNP (CSNP) and partial SNP (PSNP). SNP can be further dividedinto Level-1 CSNP, Level-2 CSNP, Level-1 PSNP and Level-2 PSNP.PSNP only lists one or more last received LSP sequence numbers, and confirmsmultiple LSPs. When detecting asynchronous LSDBs, the system asks neighbors tosend new LSPs by PSNPs.CSNP contains all LSP digest information in a LSDB, synchronizing LSDBs forneighbor routers. On a broadcast network, a DIS sends CSNPs periodically (thedefault sending period is 10 seconds). On the point-to-point line, a DIS sendsCSNPs only when the neighbors are established for the first time.ConfiguringIntegrated IS-ISAmong the following configurations, the configuration of enabling integratedIS-IS is required, while other configurations are optional.
