Pdus - HPE 5800 Series Configuration Manual

IS-IS DIS election differs from OSPF DIS election in the following ways:
•
A router with priority 0 can also participate in the DIS election.
•
When a router with a higher priority is added to the network, an LSP flooding process is
performed to elect the router as the new DIS.
As shown in
adjacencies with each other.
Figure 38 DIS in the IS-IS broadcast network
The DIS creates and updates pseudonodes, as well as generates their LSPs, to describe all routers
on the network.
A pseudonode represents a virtual node on the broadcast network. It is not a real router. In IS-IS, it is
identified by the system ID of the DIS and a one-byte Circuit ID (a non-zero value).
Using pseudonodes can reduce the resources consumed by SPF and simplify network topology.
NOTE:
On an IS-IS broadcast networks, all routers establish adjacency relationships, but they synchronize
their LSDBs through the DIS.

PDUs

PDU format
IS-IS PDUs are encapsulated in link layer frames. An IS-IS PDU has 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 39 PDU format
Figure 38, the same level routers on a network, including non-DIS routers, establish
116