HP 6125XLG R2306-HP 6125XLG Blade Switch Layer 3 - IP Routing Configuration Gu - Page 124

NOTE: On an IS-IS broadcast network, all routers establish adjacency relationships, but they synchronize their LSDBs through the DIS. IS-IS PDUs PDU IS-IS PDUs are encapsulated into link layer frames. An IS-IS PDU has two parts, the headers and the variable length fields. The headers comprise the PDU common header and the PDU specific header. All PDUs have the same PDU common header. The specific headers vary by PDU type. Figure 34 PDU format Table 4 PDU types Type 15 16 17 18 20 24 25 26 27 PDU Type Level-1 LAN IS-IS hello PDU Level-2 LAN IS-IS hello PDU Point-to-Point IS-IS hello PDU Level-1 Link State PDU Level-2 Link State PDU Level-1 Complete Sequence Numbers PDU Level-2 Complete Sequence Numbers PDU Level-1 Partial Sequence Numbers PDU Level-2 Partial Sequence Numbers PDU Acronym L1 LAN IIH L2 LAN IIH P2P IIH L1 LSP L2 LSP L1 CSNP L2 CSNP L1 PSNP L2 PSNP Hello PDU IS-to-IS hello (IIH) PDUs are used by routers to establish and maintain neighbor relationships. On broadcast networks, Level-1 routers use Level-1 LAN IIHs, and Level-2 routers use Level-2 LAN IIHs. The P2P IIHs are used on point-to-point networks. LSP The LSPs carry link state information. LSPs include Level-1 LSPs and Level-2 LSPs. The Level-2 LSPs are sent by the Level-2 routers, and the Level-1 LSPs are sent by the Level-1 routers. The Level-1-2 router can send both types of LSPs. SNP A sequence number PDU (SNP) describes the complete or partial LSPs for LSDB synchronization. SNPs include CSNP and PSNP, which are further divided into Level-1 CSNP, Level-2 CSNP, Level-1 PSNP, and Level-2 PSNP. 113