H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – IPv4 Routing
H3C S7500E Series Ethernet Switches Chapter 4 IS-IS Configuration
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Figure 4-10 LSDB overload
z IS Type: Type of the router generating the LSP.
V. SNP format
The Sequence Number PDU (SNP) confirms the latest received LSPs. It is similar to
the Acknowledge packet, but more efficient.
SNP contains Complete SNP (CSNP) and Partial SNP (PSNP), which are further
divided into Level-1 CSNP, Level-2 CSNP, Level-1 PSNP and Level-2 PSNP.
CSNP covers the summary of all LSPs in the LSDB to synchronize the LSDB between
neighboring routers. On broadcast networks, CSNP is sent by the DIS periodically (10s
by default). On point-to-point networks, CSNP is only sent during the first adjacency
establishment.
The CSNP packet format is shown in
Figure 4-11.
Figure 4-11 L1/L2 CSNP format