140
Hello PDU
IS-to-IS hello (IIH) PDUs are used by routers to establish and maintain neighbor relationships. On
broadcast networks, Level-1 routers use Level-1 LAN IIHs, and Level-2 routers use Level-2 LAN IIHs.
The P2P IIHs are used on point-to-point networks.
LSP
The LSPs carry link state information. LSPs include Level-1 LSPs and Level-2 LSPs. The Level-2
LSPs are sent by the Level-2 routers, and the Level-1 LSPs are sent by the Level-1 routers. The
Level-1-2 router can send both types of LSPs.
SNP
A sequence number PDU (SNP) describes the complete or partial LSPs for LSDB synchronization.
SNPs include CSNP and PSNP, which are further divided into Level-1 CSNP, Level-2 CSNP, Level-1
PSNP, and Level-2 PSNP.
A CSNP describes the summary of all LSPs for LSDB synchronization between neighboring routers.
On broadcast networks, CSNPs are sent by the DIS periodically (every 10 seconds by default).
A PSNP only contains the sequence numbers of one or multiple latest received LSPs. It can
acknowledge multiple LSPs at one time. When LSDBs are not synchronized, a PSNP is used to
request missing LSPs from a neighbor.
CLV
The variable fields of PDU comprise multiple Code-Length-Value (CLV) triplets.
Figure 40 CLV format
shows that different PDUs contain different CLVs. Codes 1 through 10 are defined in ISO
10589 (code 3 and 5 are not shown in the table). Codes 128 through 132 are defined in RFC 1195.
Codes 222 through 237 are defined in RFC 5120.
Table 12 CLV codes and PDU types
CLV Code
Name
PDU Type
1
Area Addresses
IIH, LSP
2
IS Neighbors (LSP)
LSP
4
Partition Designated Level 2 IS
L2 LSP
6
IS Neighbors (MAC Address)
LAN IIH
7
IS Neighbors (SNPA Address)
LAN IIH
8
Padding
IIH
9
LSP Entries
SNP
10
Authentication Information
IIH, LSP, SNP
128
IP Internal Reachability Information
LSP
129
Protocols Supported
IIH, LSP
130
IP External Reachability Information
L2 LSP
No. of Octets
1
1
Length
Code
Length
Value
Summary of Contents for HPE FlexNetwork 7500 series
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