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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
162 Switch Management and Operating Concepts
adjacent to the
Designated Router (DR)
are listed. The DR
includes itself in this list.
Table 5-23. Network Link Advertisement
Summary Link Advertisements
Summary link advertisements are Type 3 and 4 link state
advertisements. These advertisements are originated by Area
Border routers. A separate summary link advertisement is
made for each destination known to the router, that belongs to
the Autonomous System (AS), yet is outside the area.
Type 3 link state advertisements are used when the destination
is an IP network. In this case the advertisement’s Link State ID
field is an IP network number. When the destination is an AS
boundary router, a Type 4 advertisement is used, and the Link
State ID field is the AS boundary router’s OSPF Router ID.
Other that the difference in the Link State ID field, the format
of Type 3 and 4 link state advertisements is identical.
Link-State Age
Optio
Link-State ID
Advertising Router
Link-State Sequence Nu
Link-State Checksum
Network Mask
Summary Link Advertisement
TOS Metric
ns
mber
Length
2
s