Figure 10-42 HELLO Packet
1)
Netmask:
Netmask of the router interface forwarding Hello packet. Only when the netmask
of the forwarding interface and that of the receiving interface coincide, can these two
routers be neighbors.
2)
Hello Interval:
Interval of a sequence of Hello packets sending by the forwarding interface.
Only the routers with the same Hello interval can become neighbors.
3)
Router Priority:
This field decides the election result for DR/BDR in the network segment.
The greatest value means the highest priority of the advertising router and also the
possibility of being elected as the DR in the segment, while the value 0 means no election
right.
4)
Router Dead Interval:
When the receiving router doesn’t receive another Hello packet
update from the advertising router within the specified age time, it will delete the
advertising router from its neighbor table. Only routers with the coincident dead interval
can be neighbors.
5)
Designated Router ID:
The interface IP of the router specified by the advertising router in
the advertising interface network.
6)
Backup Designated Router ID:
The interface IP of the backup router specified by the
advertising router in the advertising interface network.
7)
Neighbor:
All the neighbor tables of the advertising router, listing the neighbor interface IP
addresses in each interface network segment.
3.
DD Packet
Two routers after becoming neighbors will send to each other the header of all routing
information in its link state database through the DD packets, in which way the receiving router
could synchronize the database.
Figure 10-43 DD Packet
1)
Interface MTU:
Size in bytes of the largest IP packet that can be sent out by the routing
interface of the advertising router.
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