H3C S5500-EI Configuration Manual page 154

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Hello
Hello packets are used by routers to establish and maintain neighbor relationships. A hello packet is also
an IS-to-IS hello PDU (IIH). For broadcast networks, the Level- 1 routers use the Level- 1 LAN IIHs; and the
Level-2 routers use the Level-2 LAN IIHs. The P2P IIHs are used on point-to-point networks.
Figure 55 illustrates the hello packet format in broadcast networks, where the blue fields are the common
header.
Figure 55 L1/L2 LAN IIH format
Major fields of the L1/L2 LAN IIH are as follows:
• Reserved/Circuit type: The first six bits are reserved with a value of 0. The last two bits indicate the
router type. Here, 00 means reserved, 01 indicates L1, 10 indicates L2, and 1 1 indicates L1/2.
Source ID: System ID of the router advertising the hello packet.
•
Holding time: If no hello packets are received from the neighbor within the holding time, the
•
neighbor is considered down.
• PDU length: Total length of the PDU in bytes.
PDU Type
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
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Acronym
P2P IIH
L1 LSP
L2 LSP
L1 CSNP
L2 CSNP
L1 PSNP
L2 PSNP