H3C S3610-28P Operation Manual page 443

Operation Manual – IPv4 Routing
H3C S3610&S5510 Series Ethernet Switches
III. 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 4-7
fields are the common header.
Figure 4-7 L1/L2 LAN IIH format
Reserved/Circuit Type: The first 6 bits are reserved with value 0. The last 2 bits
indicates router types: 00 means reserved, 01 indicates L1, 10 indicates L2, and
11 indicates L1/2.
Source ID: The system ID of the router advertising the hello packet.
Holding Time: If no hello packets are received from a neighbor within the holding
time, the neighbor is considered dead.
PDU Length: The total length of the PDU in bytes.
Priority: DIS priority.
LAN ID: Includes the system ID and one byte pseudonode ID.
Figure 4-8
illustrates the hello packet format in broadcast networks, where the blue
shows the hello packet format on the point-to-point network.
4-10
Chapter 4 IS-IS Configuration