132
NOTE:
On IS-IS broadcast networks, all routers are adjacent with each other. However, the DIS is responsible for
the synchronization of their LSDBs.
IS-IS PDU format
PDU header format
IS-IS packets are encapsulated into link layer frames. The Protocol Data Unit (PDU) consists of two parts,
the headers and the variable length fields. The headers comprise the PDU common header and the PDU
specific header. All PDUs have the same PDU common header. The specific headers vary by PDU type.
Figure 53 PDU format
Common header format
Figure 54 PDU common header format
Major fields of the PDU common header are as follows:
• Intradomain routing protocol discriminator—Set to 0x83.
• Length indicator—Length of the PDU header in bytes, including both common and specific headers.
• Version/Protocol ID extension—Set to 1(0x01).
• ID length—Length of the NSAP address and NET ID.
• R (Reserved)—Set to 0.
• PDU type—See Table 4.
• Ve
rsion—Set to 1(0x01).
• Maximum area address—Maximum number of area addresses supported.
Table 4 PDU type
T
e PDU T
e Acron
m
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
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
To Next Page
Loading...
Need help?
General
