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Figure 6- 101.Hello Packet
Field Description
Network Mask The network mask associated with this interface.
Options The optional capabilities supported by the router.
Hello Interval The number of seconds between this router’s Hello packets.
Router Priority This router’s Router Priority.The Router Priority is used in the election of the DR and BDR.If this field is set
to 0,the router is ineligible become the DR or the BDR.
Router Dead Interval The n
umber of seconds that m
ust pass bef
or
e declaring a silent r
outer as down.
Designated Router The identity of the DR f
or this netw
ork,
in the vie
w of the adv
er
tising r
outer
.The DR is identified here by its IP
interface address on the network.
Backup Designated Router The identity of the Backup Designated Router (BDR) for this network.The BDR is identified here by its IP
interface address on the network.This field is set to 0.0.0.0 if there is no BDR.
Neighbor The Router IDs of each r
outer from whom valid Hello packets have been seen within the Router Dead Interval
on the network.
Data
base Descr
iption P
ack
et
Database Description packets are OSPF packet type 2.These packets are exchanged when an adjacency is being initialized.They describe the contents of the
topological database
.
Multiple pack
ets ma
y be used to describe the database
.
For this purpose a poll-response procedure is used.One of the routers is designated
to be master,the other a slave.The master seconds Database Description packets (polls) that are acknowledged by Database Description packets sent by the
sla
ve (responses).The responses are linked to the polls via the packets’ DD sequence numbers.
109
Allied Telesyn AT-9724TS High-Density Layer 3 Stackable Gigabit Ethernet Switch
V
ersion No.
1
Pack
et Length
Octets
0
123
OSPF Hello Pack
et
Router ID
Ar
ea ID
Checksum
Authentication Type
Authentication
Authentication
Network Mask
Options
Router Priority
Hello Interval
Router Dead Inter
val
Designated Router
Backup Designated Router
Neighbour
4