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DES-3326S Layer 3 Fast Ethernet Switch User’s Guide
148 Switch Management and Operating Concepts
The Link-State Request Packet
Link-State Request packets are OSPF packet type 3. After
exchanging Database Description packets with a neighboring
router, a router may find that parts of its topological database
are out of date. The Link-State Request packet is used to
request the pieces of the neighbor’s database that are more up
to date. Multiple Link-State Request packets may need to be
used. The sending of Link-State Request packets is the last
step in bringing up an adjacency.
A router that sends a Link-State Request packet has in mind
the precise instance of the database pieces it is requesting,
defined by LS sequence number, LS checksum, and LS age,
although these fields are not specified in the Link-State
Request packet itself. The router may receive even more recent
instances in response.
The format of the Link-State Request packet is shown below:
Version No.
Pa
Router ID
Area ID
Au
Authentication
Authentication
Checksum
Link-State Request Packet
3
Link-State Type
Link-State ID
Advertising Router
cket Length
thentication Type