332 CHAPTER 29: IS-IS CONFIGURATION
Figure 104 PDU common header format
■ Intra-domain Routing Protocol Discriminator: Set to 0x83.
■ Length Indicator: The length of the PDU header, including both common and
specific headers, present in bytes.
■ Version/Protocol ID Extension: Set to 1(0x01).
■ ID Length: The length of the NSAP address and NET ID.
■ R (Reserved): Set to 0.
■ PDU Type: For detail information, refer to Table 44.
■ Version: Set to 1(0x01).
■ Maximum Area Address: Maximum number of area addresses supported.
Hello
The hello packet is used by routers to establish and maintain the neighbor
relationship. It is also called IS-to-IS hello PDU (IIH). For broadcast network, the
Level-1 router uses the Level-1 LAN IIH; and the Level-2 router uses the Level-2
LAN IIH. The P2P IIH is used on point-to-point network.
Figure 105 illustrates the hello packet format in broadcast networks, where the
blue fields are the common header.
Table 44 PDU type
Type PDU Type Acronym
15 Level-1 LAN IS-IS hello PDU L1 LAN IIH
16 Level-2 LAN IS-IS hello PDU L2 LAN IIH
17 Point-to-Point IS-IS hello PDU P2P IIH
18 Level-1 Link State PDU L1 LSP
20 Level-2 Link State PDU L2 LSP
24 Level-1 Complete Sequence Numbers PDU L1 CSNP
25 Level-2 Complete Sequence Numbers PDU L2 CSNP
26 Level-1 Partial Sequence Numbers PDU L1 PSNP
27 Level-2 Partial Sequence Numbers PDU L2 PSNP
Intradomain routing protocol discriminator
Reserved
Version
R
ID length
Version/Protocol ID extension
Length indicator
Maximum area address
R R PDU type
No. of Octets
1
1
1
1
1
1
1
1
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