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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Using pseudonodes can reduce the resources used by SPF and simplify the network
topology.
 Note:
On IS-IS broadcast networks, all routers are adjacent with each other. The DIS is
responsible for the synchronization of their LSDBs.
4.1.4 IS-IS PDU Format
I. PDU header format
The IS-IS packets are encapsulated into link layer frames. The Protocol Data Unit (PDU)
consists of two parts, the headers and the variable length field, where the headers can
be further divided into the common header and the specific header. The common
headers are the same for all PDUs, while the specific headers vary by PDU type. The
following figure shows the PDU format.
Figure 4-5 PDU format
II. Common header format
Figure 4-6 shows the common header format.
Figure 4-6 PDU common header format
z Intradomain Routing Protocol Discriminator: Set to 0x83.
z Length Indicator: The length of the PDU header, including both common and
specific headers, present in bytes.
z Version/Protocol ID Extension: Set to 1(0x01).
z ID Length: The length of the NSAP address and NET ID.