DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
Switch Management and Operating Concepts 151
AllSPFRouters, to the multicast address AllDRouters, or as a
unicast packet.
The format of this packet is similar to that of the Data
Description packet. The body of both packets is simply a list of
link-state advertisement headers.
The format of the Link-State Acknowledgment packet is shown
below:
Version No.
Pa
Router ID
Area ID
Au
Authentication
Authentication
Checksum
Link-State Acknowledgment P
5
Link-State Advertisement
cket Length
thentication Type
acket
Header ...
Figure 5-27. Link-State Acknowledgement Packet
Each acknowledged link-state advertisement is described by its
link-state advertisement header. It contains all the information
required to uniquely identify both the advertisement and the
advertisement’s current instance.
Link-State Advertisement Formats
There are five distinct types of link-state advertisements. Each
link-state advertisement begins with a standard 20-byte link-
state advertisement header. Succeeding sections then diagram
the separate link-state advertisement types.
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